truffle: graal/com.oracle.max.graal.doc.initial/graal

annotate graal/com.oracle.max.graal.doc.initial/graal_compiler.tex @ 2892:5005a5607506

Moved design doc to graal project directory.

author	Thomas Wuerthinger <thomas@wuerthinger.net>
date	Wed, 08 Jun 2011 14:06:17 +0200
parents	doc/design/graal_compiler.tex@3396862d4cee
children	5d4aa5672d3d

rev	line source
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	1 \documentclass[twocolumn]{svjour3}
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	2 \usepackage{listings}
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	3 \usepackage[pdftex]{graphicx}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	4 \usepackage{environ}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	5 \usepackage{amsmath}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	6 \usepackage{amsfonts}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	7 \usepackage[english]{babel}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	8 \usepackage[utf8]{inputenc}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	9 \usepackage{lmodern}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	10 \usepackage[T1]{fontenc}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	11 \usepackage{color}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	12
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	13 \input{graphdrawing}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	14
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	15 \renewcommand*\descriptionlabel[1]{\hspace\labelsep\normalfont\bf #1}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	16
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	17 \newcommand{\Sa}{{\Large$^*$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	18 \newcommand{\Sb}{{\Large$^\dag$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	19 \newcommand{\Sc}{{\Large$^\S$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	20
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	21
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	22 \newcommand{\mynote}[2]{
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	23 \textcolor{red}{\fbox{\bfseries\sffamily\scriptsize#1}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	24 {\small\textsf{\emph{#2}}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	25 \fbox{\bfseries\sffamily\scriptsize }}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	26
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	27 \newcommand\TODO[1]{\mynote{TODO}{#1}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	28 \newcommand\cw[1]{\mynote{CW}{#1}}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	29 \newcommand\ls[1]{\mynote{LS}{#1}}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	30 \newcommand\nodename[1]{\texttt{#1}}
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	31
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	32
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	33
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	34 \smartqed % flush right qed marks, e.g. at end of proof
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	35
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	36 \journalname{Graal Compiler Design}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	37 \def\makeheadbox{{%
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	38 \hbox to0pt{\vbox{\baselineskip=10dd\hrule\hbox
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	39 to\hsize{\vrule\kern3pt\vbox{\kern3pt
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	40 \hbox{\bfseries The Graal Compiler - Design and Strategy}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	41 \kern3pt}\hfil\kern3pt\vrule}\hrule}%
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	42 \hss}}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	43
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	44 \begin{document}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	45
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	46 \author{Thomas W\"{u}rthinger \Sa, Lukas Stadler \Sc, Gilles Duboscq \Sa}
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	47 \institute{\Sa Oracle, \Sc Johannes Kepler University, Linz}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	48
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	49 \date{Created: \today}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	50
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	51 \title{The Graal Compiler}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	52 \subtitle{Design and Strategy \\ \textcolor{red}{work in progress (Oracle internal)}}
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	53
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	54 \maketitle
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	55
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	56 \abstract{
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	57 The Graal compiler (simply referred to as \emph{the compiler} in the rest of this document) aims at improving upon C1X, the Java port of the HotSpot client compiler, both in terms of modularity and peak performance.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	58 The compiler should work with the Maxine VM and the HotSpot VM.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	59 This document contains information about the proposed design and strategy for developing the compiler.}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	60
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	61 \section{Context}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	62
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	63 In 2009, the Maxine team started with creating C1X, a Java port of the HotSpot client compiler, and integrated it into the Maxine VM.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	64 Part of this effort was the development of a clear and clean compiler-runtime interface that allows the separation of the compiler and the VM.
c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	65 This compiler-runtime interface enables the use of one compiler for multiple VMs.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	66 In June 2010, we started integrating C1X into the HotSpot VM and we called the resulting system Graal~VM.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	67 Currently, the Graal~VM is fully functional and runs benchmarks (SciMark, DaCapo) at a similar speed as the HotSpot client compiler.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	68
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	69 \section{Goals}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	70 The compiler effort aims at rewriting the high-level intermediate representation of C1X with two main goals:
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	71 \begin{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	72 \item[Modularity:] A modular design of the compiler should simplify the implementation of new languages, new back-ends, and new optimizations.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	73 \item[Peak Performance:] A more powerful intermediate representation should enable the implementation of aggressive optimizations that impact the peak performance of the resulting machine code.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	74 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	75
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	76 \section{Design}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	77 For the implementation of the compiler, we rely on the following design decisions:
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	78 \begin{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	79 \item[Graph Representation:]
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	80 The compiler's intermediate representation is modeled as a graph with nodes that are connected with directed edges.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	81 There is only a single node base class and every node has an associated graph object that does not change during the node's lifetime.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	82 Every node is serializable and has an id that is unique within its graph.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	83 Every edge is classified as either a control flow edge (anti-dependency) or a data flow edge (dependency) and represented as a simple pointer from the source node to the target node.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	84 It is possible to replace a node with another node without traversing the full graph.
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	85 The graph does not allow data flow edge cycles or control flow edge cycles.
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	86 We achieve this by explicitly modeling loops (see Section~\ref{sec:loops}).
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	87 \item[Extensibility:]
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	88 The compiler is extensible by allowing developers to add new compiler phases and new node subclasses without modifying the compiler's sources.
15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	89 A node has an abstract way of expressing its semantics and new compiler phases can ask compiler nodes for their properties and capabilities.
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	90 We use the ``everything is an extension'' concept.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	91 Even standard compiler optimizations are internally modeled as extensions, to show that the extension mechanism exposes all necessary functionality.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	92 \item[Detailing:]
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	93 The compilation starts with a graph that contains nodes that represent the operations of the source language (e.g., one node for an array store to an object array).
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	94 During the compilation, the nodes are replaced with more detailed nodes (e.g., the array store node is split into a null check, a bounds check, a store check, and a memory access).
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	95 Compiler phases can choose whether they want to work on the earlier versions of the graph (e.g., escape analysis) or on later versions (e.g., null check elimination).
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	96 \item[Generality:]
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	97 The compiler does not require Java as its input.
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	98 This is achieved by having a graph as the starting point of the compilation and not a Java bytecode array.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	99 Building the graph from the Java bytecodes must happen before giving a method to the compiler.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	100 This enables front-ends for different languages (e.g., Ruby or JavaScript) to provide their own graph.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	101 Also, there is no dependency on a specific back-end, but the output of the compiler is a graph that can then be converted to a different representation in a final compiler phase.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	102 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	103
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	104 \section{Milestones}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	105 \label{sec:mile}
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	106 The compiler is being developed starting from the current C1X source code base.
3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	107 This helps us test the compiler at every intermediate development step on a variety of Java benchmarks.
3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	108 We define the following development milestones (see Section~\ref{sec:conclusions} for planned dates):
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	109 \begin{description}
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	110 \item[M1:] We have a fully working Graal~VM version with a stripped down C1X compiler that does not perform any optimization.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	111 \item[M2:] We modified the high-level intermediate representation to be based on the compiler graph data structure.
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	112 \item[M3:] We have reimplemented and reenabled compiler optimizations in the compiler that previously existed in C1X.
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	113 \item[M4:] We have reintegrated the new compiler into the Maxine VM and can use it as a Maxine VM bootstrapping compiler.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	114 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	115
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	116 After those four milestones, we see three different possible further development directions that can be followed in parallel:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	117 \begin{itemize}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	118 \item Removal of the XIR template mechanism and replacement with a snippet mechanism that works with the compiler graph.
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	119 \item Improvements for peak performance (loop optimizations, escape analysis, bounds check elimination, processing additional interpreter runtime feedback).
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	120 \item Implementation of a prototype front-end for a different language, e.g., JavaScript.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	121 \end{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	122
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	123 \section{Project Source Structure}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	124 In order to support the goal of a modular compiler, the code will be divided into the following source code projects (as subprojects of \textbf{com.oracle.max.graal}).
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	125
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	126 \begin{description}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	127 \item[graph] contains the abstract node implementation, the graph implementation and all the associated tools and auxiliary classes.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	128 \item[nodes] contains the implementation of known basic nodes (e.g., phi nodes, control flow nodes, \ldots).
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	129 Additional node classes should go into separate projects and be specializations of the known basic nodes.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	130 \item[java] contains code for building graphs from Java bytecodes and Java-specific nodes.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	131 \item[opt] contains optimizations such as global value numbering or conditional constant propagation.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	132 \item[compiler] contains the compiler, including:
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	133 \begin{itemize}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	134 \item Scheduling of the compilation phases.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	135 \item Implementation of the \emph{compiler interface} (CI).
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	136 \item Implementation of the final compilation phase that produces the low-level representation.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	137 \item Machine code creation, including debug info.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	138 \end{itemize}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	139 \end{description}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	140
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	141
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	142 \section{Graph}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	143
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	144 The \emph{intermediate representation}~(IR) of the compiler is designed as a directed graph.
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	145 The graph allocates unique ids for new nodes and can be queried for the node corresponding to a given id as well as for an unordered list of nodes of the graph.
3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	146 Graphs can manage side data structures (e.g. dominator trees and temporary schedules), which will be automatically invalidated and lazily recomputed whenever the graph changes. These side data structures will usually be understood by more than one optimization.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	147
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	148 The nodes of the graph have the following properties:
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	149 \begin{itemize}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	150 \item Each node is always associated with a single graph and this association is immutable.
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	151 \item Each node has an immutable id that is unique within its associated graph.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	152 \item Nodes can have a data dependency, which means that one node requires the result of another node as its input. The fact that the result of the first node needs to be computed before the second node can be executed introduces a partial order to the set of nodes.
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	153 \item Nodes can have a control flow dependency, which means that the execution of one node will be followed by the execution of another node. This includes conditional execution, memory access serialization and other reasons, and again introduces a partial order to the set of nodes.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	154 \item Nodes can only have data and control dependencies to nodes which belong to the same graph.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	155 \item Control dependencies and data dependencies each represent a \emph{directed acyclic graph} (DAG) on the same set of nodes. This means that data dependencies always point upwards, and control dependencies always point downwards in a drawing of the graph. Situations that normally incur cycles (like loops) are represented by special nodes (see Section~\ref{sec:loops}).
2619 1586b1b56f0c Fixed typo. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2618 diff changeset	156 \item Ordering between nodes is specified only to the extent which is required to correctly express the semantics of a given program. This gives the compiler flexibility for the possible scheduling of a node and therefore wiggle room for optimizations. For algorithms that require a fixed ordering of nodes, a temporary schedule can always be generated.
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	157 \item Both data and control dependencies can be traversed in both directions, so that each node can be traversed in four directions (see Figure~\ref{fig:directions}):
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	158 \begin{itemize}
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	159 \item \emph{inputs} are all nodes that this node has data dependencies on.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	160 \item \emph{usages} are all nodes whose inputs contain this node.
c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	161 \item \emph{successors} are all nodes that have to be after this node in control flow.
c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	162 \item \emph{predecessors} are all nodes whose successors contain this node.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	163 \end{itemize}
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	164 \item Only inputs and successors can be changed, and changes to them will update the usages and predecessors.
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	165 \item Every node must be able to support cloning and serialization.
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	166 \item The edges of a node also define \textit{happens-before} and \textit{happens-after} relationships as shown in Figure~\ref{fig:directions}.
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	167 \end{itemize}
795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	168
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	169 \begin{figure}[h]
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	170 \centering
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	171 \begin{digraphenv}{scale=0.5}{graphdirections}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	172 \node{node1}{Node}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	173 \textnode{inputs}{inputs}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	174 \textnode{usages}{usages}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	175 \textnode{successors}{successors}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	176 \textnode{predecessors}{predecessors}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	177 \data{node1}{inputs}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	178 \control{node1}{successors}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	179 \data{usages}{node1}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	180 \control{predecessors}{node1}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	181 \node{node2}{Node}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	182 \textnode{before}{happens-before}
c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	183 \textnode{after}{happens-after}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	184 \data{node2}{before}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	185 \control{node2}{after}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	186 \data{after}{node2}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	187 \control{before}{node2}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	188 \end{digraphenv}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	189 \caption{A node and its edges.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	190 \label{fig:directions}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	191 \end{figure}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	192
2687 77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	193 \subsection{Inlining}
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	194 Inlining is always performed by embedding one graph into another graph.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	195 Nodes cannot be reassigned to another graph, they are cloned instead.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	196 Therefore, inlining is performed by copying and rewiring the nodes of the inlined method into the graph of the outer method.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	197 While the copying will decrease compilation performance, it enables us to cache the graph for the inlined method, optimize it independently from the outer method, and use the optimized graph for subsequent inlinings.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	198 We do not expect a significant negative impact on overall compilation performance.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	199
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	200 We are able to perform the inlining at any point during the compilation of a method and can therefore selectively expand the inlining if a certain optimization turns out to depend on the inlining of a method.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	201 An example for this would be when the escape analysis finds out that a certain object only escapes because of one method call and this method call is not inlined, because the penalty was to high.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	202 In this case, we can chose to nevertheless inline the method in order to increase the chances for finding out that the object does not escape.
77e106760633 Additional subsection on inlining. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2685 diff changeset	203
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	204 \section{Control Flow}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	205
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	206 Control flow is managed in way where the predecessor node contains direct pointers to its successor nodes.
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	207 We reserve the term \textit{instruction} for nodes that are embedded in the control flow.
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	208 This is opposite to the approach taken in the server compiler, where control flow and data flow edges point in the same direction.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	209 The advantage that we see in our approach is that there is no need for projection nodes in case of control flow splits.
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	210 An \texttt{If} instruction can directly point to its true and false successors without any intermediate nodes.
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	211 This makes the graph more compact and simplifies graph traversal.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	212
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	213 Listing~\ref{lst:cfg2} shows an example Java program with an if statement where both paths do not contain any instruction with side effects.
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	214 The \texttt{If} instruction can directly point its true and false successors to a \texttt{Merge} instruction.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	215 A \texttt{Phi} node that selects the appropriate value is appended to the \texttt{Merge} instruction.
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	216 The \texttt{Return} instruction then has a data dependency on the \texttt{Phi} node.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	217
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	218 \begin{lstlisting}[label=lst:cfg2, caption=Control flow in the graph., captionpos=b]
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	219 if (condition) { return 0; }
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	220 else { return 1; }
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	221 \end{lstlisting}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	222
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	223 \begin{figure}[h]
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	224 \centering
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	225 \begin{digraphenv}{scale=0.5}{cfg2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	226 \textnode{entry}{Entry}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	227 \textnode{condition}{condition}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	228 \textnode{const0}{0}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	229 \textnode{const1}{1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	230 \nodesplit{if}{If}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	231 \control{entry}{if}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	232 \controllabel{if:succ1}{merge}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	233 \controllabel{if:succ2}{merge}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	234 \data{if}{condition}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	235 \node{merge}{Merge}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	236 \node{return}{Return}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	237 \nodetri{phi}{Phi}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	238 \datalabel{phi:in1}{merge}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	239 \datalabel{phi:in2}{const0}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	240 \datalabel{phi:in3}{const1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	241 \data{return}{phi}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	242 \control{merge}{return}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	243 \end{digraphenv}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	244 \caption{A simple loop with two exits.}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	245 \label{fig:exc1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	246 \end{figure}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	247
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	248 \section{Exceptions}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	249 \label{sec:Exceptions}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	250
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	251 We do not throw runtime exceptions (e.g., \texttt{IndexOutOf\-BoundsException}, \texttt{NullPointerException}, or \texttt{Out\-Of\-MemoryException}), but deoptimize instead.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	252 This reduces the places in the compiled code where an exact bytecode location and debug information must be known.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	253 Additionally, this greatly reduces the number of exception handler edges in the compiled code.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	254 The main advantage of this technique is however, that we are free in moving around bounds checks, memory allocation, memory accesses with implicit null checks, etc.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	255
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	256 There are only two kinds of instruction that need explicit exception edges, because they are the only instructions that can throw exceptions in compiled code: \texttt{Throw} instructions and \texttt{Invoke} instructions.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	257 They are modelled as instructions with an additional control flow continuation that points to an \texttt{ExceptionDispatch} instruction.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	258 The exception dispatch instruction decides based on the type of the exception object whether the control should flow to the catch handler or to another exception dispatch.
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	259 If there is no catch handler in the currently compiled method, then the control flows into the \texttt{Unwind} instruction that handles the exception by forwarding it to the caller.
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	260 Listing~\ref{lst:exc1} shows an example Java program with nested try blocks and Figure \ref{fig:exc1} shows the corresponding compiler graph.
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	261
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	262 \begin{lstlisting}[label=lst:exc1, caption=Exception dispatch in the compiler graph., captionpos=b]
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	263 try { m1();
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	264 try { m2();
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	265 } catch(ExtendedException e) { ... }
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	266 m3();
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	267 throw exception;
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	268 } catch(Exception e) { ... }
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	269 \end{lstlisting}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	270
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	271 \begin{figure}[h]
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	272 \centering
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	273 \begin{digraphenv}{scale=0.5}{exc1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	274 \textnode{entry}{Entry}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	275 \textnode{catch1}{catch1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	276 \textnode{catch2}{catch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	277 \nodesplit{m1}{Invoke m1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	278 \nodesplit{m2}{Invoke m2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	279 \nodesplit{m3}{Invoke m3}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	280 \nodesplit{dispatch1}{ExceptionDispatch}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	281 \nodesplit{dispatch2}{ExceptionDispatch}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	282 \node{throw}{Throw}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	283 \node{unwind}{Unwind}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	284 \control{entry}{m1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	285 \controllabel{m1:succ1}{m2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	286 \controllabel{m1:succ2}{dispatch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	287 \controllabel{m2:succ1}{m3}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	288 \controllabel{m2:succ2}{dispatch1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	289 \controllabel{m3:succ1}{throw}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	290 \controllabel{m3:succ2}{dispatch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	291 \control{throw}{dispatch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	292 \controllabel{dispatch1:succ2}{catch1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	293 \controllabel{dispatch1:succ1}{dispatch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	294 \controllabel{dispatch2:succ2}{catch2}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	295 \controllabel{dispatch2:succ1}{unwind}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	296 \end{digraphenv}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	297 \caption{A simple loop with two exits.}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	298 \label{fig:exc1}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	299 \end{figure}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	300
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	301 \section{Loops}
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	302 \label{sec:loops}
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	303 Loops form a first-class construct in the IR that is expressed by specialized IR nodes during all optimization phases.
15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	304 We only compile methods with a control flow where every loop has a single entry point.
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	305 This entry point is a \nodename{LoopBegin} instruction.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	306 This instruction is connected to a \nodename{LoopEnd} instruction that merges all control flow paths that do not exit the loop.
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	307 The edge between the \nodename{LoopBegin} and the \nodename{LoopEnd} is the backedge of the loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	308 It goes from the beginning to the end in order to make the graph acyclic.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	309 An algorithm that traverses the control flow has to explicitely decide whether it wants to incorporate backedges (i.e., special case of the treatment of \nodename{LoopEnd}) or ignore them.
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	310 Figure \ref{fig:loop1} shows a simple example with a loop with a single entry and two exits.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	311
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	312 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	313 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	314 \begin{digraphenv}{scale=0.5}{layout1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	315 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	316 \textnode{Exit1}{First loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	317 \textnode{Exit2}{Second loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	318 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	319 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	320 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	321 \nodesplit{If2}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	322 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	323 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	324 \controllabel{If1:succ1}{If2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	325 \controllabel{If2:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	326 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	327 \controllabel{If1:succ2}{Exit1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	328 \controllabel{If2:succ2}{Exit2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	329 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	330 \caption{A simple loop with two exits.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	331 \label{fig:loop1}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	332 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	333
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	334 \subsection{Loop Phis}
2688 3396862d4cee Minor design doc edits. Doug Simon <doug.simon@oracle.com> parents: 2687 diff changeset	335 Data flow in loops is modeled with special phi nodes at the beginning and the end of the loop.
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	336 The \nodename{LoopEnd} instruction merges every value that flows into the next loop iteration in associated \nodename{LoopEndPhi} nodes.
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	337 A corresponding \nodename{LoopBeginPhi} node that is associated with the loop header has a control flow dependency on the \nodename{LoopEndPhi} node.
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	338 Listing~\ref{lst:loop} shows a simple counting loop that is used as an example in the rest of this section.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	339 Figure~\ref{fig:loop2} shows how the loop is modelled immediately after building the graph.
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	340
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	341 \begin{lstlisting}[label=lst:loop, caption=Loop example that counts from 0 to n-1., captionpos=b]
2678 b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	342 for(int i=0; i<n; ++i) { }
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	343 \end{lstlisting}
b9b0a0aa7ee8 Added addition sections on control flow and exceptions. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2619 diff changeset	344
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	345 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	346 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	347 \begin{digraphenv}{scale=0.5}{layout2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	348 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	349 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	350 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	351 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	352 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	353 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	354 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	355 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	356 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	357 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	358 \nodebi{Compare}{<}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	359 \nodebi{LoopBeginPhi}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	360 \nodebi{Add}{+}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	361 \datalabel{Add:in1}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	362 \datalabel{Add:in2}{Constant1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	363 \nodebi{LoopEndPhi}{LoopEndPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	364 \control{LoopBeginPhi}{LoopEndPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	365 \data{LoopEndPhi:in1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	366 \data{LoopEndPhi:in2}{Add}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	367 \datalabel{LoopBeginPhi:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	368 \datalabel{LoopBeginPhi:in2}{Constant0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	369 \datalabel{Compare:in1}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	370 \datalabel{Compare:in2}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	371 \data{If1}{Compare}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	372 \controllabel{If1:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	373 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	374 \controllabel{If1:succ2}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	375 \end{digraphenv}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	376 \caption{Graph for a loop counting from 0 to n-1.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	377 \label{fig:loop2}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	378 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	379
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	380 \subsection{Loop Counters}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	381 The compiler is capable of recognizing variables that are only increased within a loop.
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	382 A potential overflow of such a variable is prohibited with a guard before the loop (this is not necessary in this example, because the loop variable cannot overflow).
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	383 Figure \ref{fig:loop3} shows the compiler graph of the example loop after the loop counter transformation.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	384
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	385
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	386 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	387 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	388 \begin{digraphenv}{scale=0.5}{layout3}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	389 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	390 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	391 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	392 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	393 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	394 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	395 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	396 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	397 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	398 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	399 \nodebi{Compare}{<}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	400 \nodetri{LoopCounter}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	401 \datalabel{LoopCounter:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	402 \datalabeltext{LoopCounter:in2}{Constant0}{init}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	403 \datalabeltext{LoopCounter:in3}{Constant1}{stride}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	404 \datalabel{Compare:in1}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	405 \datalabel{Compare:in2}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	406 \data{If1}{Compare}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	407 \controllabel{If1:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	408 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	409 \controllabel{If1:succ2}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	410 \end{digraphenv}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	411 \caption{Graph after loop counter transformation.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	412 \label{fig:loop3}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	413 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	414
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	415 \subsection{Bounded Loops}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	416
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	417 If the total maximum number of iterations of a loop is fixed, then the loop is converted into a bounded loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	418 The total number of iterations always denotes the number of full iterations of the loop with the control flowing from the loop begin to the loop end.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	419 If the total number of iterations is reached, the loop is exited directly from the loop header.
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	420 In the example, we can infer from the loop exit with the comparison on the loop counter that the total number of iterations of the loop is limited to n.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	421 Figure \ref{fig:loop4} shows the compiler graph of the example loop after the bounded loop transformation.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	422
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	423 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	424 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	425 \begin{digraphenv}{scale=0.5}{layout4}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	426 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	427 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	428 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	429 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	430 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	431 \nodesplittri{LoopBegin}{BoundedLoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	432 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	433 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	434 \controllabel{LoopBegin:succ2}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	435 \controllabel{LoopBegin:succ3}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	436 \nodetri{LoopCounter}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	437 \datalabel{LoopCounter:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	438 \datalabeltext{LoopCounter:in2}{Constant0}{init}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	439 \datalabeltext{LoopCounter:in3}{Constant1}{stride}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	440 \data{LoopBegin}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	441 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	442 \end{digraphenv}
2589 795df30f979d Refer to "Graal compiler" as "the compiler" in the design document. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2588 diff changeset	443 \caption{Graph after bounded loop transformation.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	444 \label{fig:loop4}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	445 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	446
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	447 \subsection{Vectorization}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	448
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	449 If we have now a bounded loop with no additional loop exit and no associated phi nodes (only associated loop counters), we can vectorize the loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	450 We replace the loop header with a normal instruction that produces a vector of values from 0 to the number of loop iterations minus 1.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	451 The loop counters are replaced with \texttt{VectorAdd} and \texttt{VectorMul} nodes.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	452 The vectorization is only possible if every node of the loop can be replaced with a corresponding vector node.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	453 Figure \ref{fig:loop5} shows the compiler graph of the example loop after vectorization.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	454 The vector nodes all work on an ordered list of integer values and are subject to canonicalization and global value numbering like any other node.
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	455
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	456
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	457 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	458 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	459 \begin{digraphenv}{scale=0.5}{layout5}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	460 \textnode{Entry}{Entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	461 \textnode{Exit}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	462 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	463 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	464 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	465 \node{Vector}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	466 \nodebi{VectorAdd}{VectorAdd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	467 \nodebi{VectorMul}{VectorMul}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	468 \control{Entry}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	469 \control{Vector}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	470 \datalabel{VectorAdd:in1}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	471 \datalabel{VectorAdd:in2}{Constant0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	472 \datalabel{VectorMul:in1}{VectorAdd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	473 \datalabel{VectorMul:in2}{Constant1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	474 \data{Vector}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	475 \end{digraphenv}
2598 e4395464810e Made graphs smaller. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2597 diff changeset	476 \caption{Graph after vectorization.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	477 \label{fig:loop5}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	478 \end{figure}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	479
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	480
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	481 \section{Frame States}
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	482 A frame state captures the state of the program like it is seen in by an interpreter of the program.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	483 The frame state contains the information that is local to the current activation and will therefore disappear during SSA-form constructions or other compiler optimizations.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	484 For Java, the frame state is defined in terms of the Java bytecode specification (i.e., the values of the local variables, the operand stack, and the locked monitors).
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	485 However, a frame state is not a concept specific to Java (e.g., the Crankshaft JavaScript engine uses frame states in their optimizing compiler to model the values of the AST interpreter).
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	486
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	487 Frame states are necessary to support the deoptimization of the program, which is the precondition for performing aggressive optimizations that use optimistic assumptions.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	488 Therefore every point in the optimizing compiler that may revert execution back to the interpreter needs a valid frame state.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	489 However, the point where the interpreter continues execution need not correspond exactly to the execution position of the compiled code, because many Java bytecode instructions can be safely reexecuted.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	490 Thus, frame states need only be generated for the states after instructions that cannot be reexecuted, because they modify the state of the program.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	491 Examples for such instructions are:
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	492
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	493 \begin{itemize}
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	494 \item Array stores (in Java bytecodes {\tt IASTORE, LASTORE, FASTORE, \\DASTORE, AASTORE, BASTORE, CASTORE, SASTORE})
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	495 \item Field stores (in Java bytecodes {\tt PUTSTATIC, PUTFIELD})
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	496 \item Method calls (in Java bytecodes {\tt INVOKEVIRTUAL, INVOKESPECIAL, \\INVOKESTATIC, INVOKEINTERFACE})
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	497 \item Synchronization (in Java bytecodes {\tt MONITORENTER, MONITOREXIT})
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	498 \end{itemize}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	499
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	500 Within the graph a frame state is represented as a node that is attached to the instruction that caused it to be generated using a control dependency (see Figure~\ref{fig:fs1}).
2598 e4395464810e Made graphs smaller. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2597 diff changeset	501 Frame states also have data dependencies on the contents of the state: the local variables and the expression stack.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	502
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	503 The frame state at the method beginning does not have to be explicitely in the graph, because it can always be reconstructed at a later stage.
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	504 We save the frame state at control flow merges if there is at least one frame state on any control flow path between a node and its immediate dominator.
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	505
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	506
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	507 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	508 \centering
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	509 \begin{digraphenv}{scale=0.5}{fs1}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	510 \nodetrisplit{store1}{ArrayStore}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	511 \nodebi{load1}{ArrayLoad}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	512 \controllabel{store1:succ1}{load1}
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	513 \nodetrisplit{store2}{FieldStore}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	514 \control{load1}{store2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	515 end [shape=plaintext, label="...", width="2.0"]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	516 store2:succ1:s -> end:n [color=red];
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	517 %
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	518 \nodeframestate{fs1}{FrameState}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	519 \controllabel{store1:succ2}{fs1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	520 \nodeframestate{fs2}{FrameState}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	521 \controllabel{store2:succ2}{fs2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	522 \end{digraphenv}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	523 \caption{Simple example using two frame states.}
2604 c9b17ac5c06b Doc fixes. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2598 diff changeset	524 \label{fig:fs1}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	525 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	526
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	527
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	528 A deoptimization node needs a valid frame state that specifies the location and state where the interpreter should continue.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	529 The algorithm for constructing frame states makes sure that every possible location in the graph has a well-defined frame state that can be used by a deoptimization instruction.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	530 Therefore, there are no direct links between the deoptimization instruction and its frame state thus allowing the deoptimization instructions to move freely around.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	531
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	532 \subsection{Partial Escape Analysis}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	533
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	534 A partial escape analysis can help to further reduce the number of frame states.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	535 A field or array store does not create a new frame state, when the object that is modified did not have a chance to escape between its creation and the store.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	536
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	537 Listing~\ref{lst:escape1} shows an example of a method that creates two \texttt{Point} objects, connects them, and returns them.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	538 The object allocation of the first \texttt{Point} object does not need a frame state.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	539 We can always reexecute the \texttt{NEW} bytecode again in the interpreter.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	540 The \texttt{Point} object allocated by the compiler will then simply disappear after the next garbage collection.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	541 The following field store is a thread-local memory store, because the \texttt{Point} object did not have any chance to escape.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	542 Same applies to the assignment of the \texttt{next} field and the third field assignment.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	543 Therefore, the whole method \texttt{getPoint} does not need an explicit frame state, because at any time during execution of this method, we can deoptimize and continue execution in the interpreter at the first bytecode of the method.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	544
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	545 \begin{lstlisting}[label=lst:escape1, caption=Example method that needs no frame state., captionpos=b]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	546 void getPoint() {
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	547 Point p = new Point();
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	548 p.x = 1;
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	549 p.next = new Point();
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	550 p.next.x = 2;
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	551 return p;
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	552 }
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	553 \end{lstlisting}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	554
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	555 The reduction of frame states makes it easier for the compiler to perform memory optimizations like memory access coalescing.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	556 We believe that this reduction on frame states is the key to effective vectorization and other compiler optimizations where compilers of compilers of unmanaged languages have advantages.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	557
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	558 \subsection{Guards}
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	559 A guard is a node that deoptimizes based on a conditional expression.
07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	560 Guards are not attached to a certain frame state, they can move around freely and will always use the correct frame state when the nodes are scheduled (i.e., the last emitted frame state).
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	561 The node that is guarded by the deoptimization has a data dependency on the guard and the guard in turn has a data dependency on the condition.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	562 A guard must not be moved above any \texttt{If} nodes.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	563 Therefore, we use \texttt{Anchor} instructions after a control flow split and a data dependency from the guard to this anchor.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	564 The anchor is the most distant instruction that is postdominated by the guarded instruction and the guard can be scheduled anywhere between those two nodes.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	565 This ensures maximum flexibility for the guard instruction and guarantees that we only deoptimize if the control flow would have reached the guarded instruction (without taking exceptions into account).
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	566
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	567 To illustrate the strengths of this approach, we show the graph for the Java code snippet shown in \ref{lst:guard1}.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	568 The example looks artificial, but in case of method inlining, this is a pattern that is not unlikely to be present in a normal Java program.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	569 Figure \ref{fig:guard0} shows the compiler graph for the example method after graph building.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	570 The field stores are both represented by a single instruction and the null check that is implicitely incorporated in the field store.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	571
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	572 \begin{lstlisting}[label=lst:guard1, caption=Example method that demonstrates the strengths of modelling the guards explicitely., captionpos=b]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	573 void init(Point p) {
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	574 if (p != null) {
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	575 p.x = 0;
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	576 }
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	577 p.y = 0;
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	578 }
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	579 \end{lstlisting}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	580
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	581 \begin{figure}[h]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	582 \centering
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	583 \begin{digraphenv}{scale=0.5}{guard0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	584 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	585 \nodesplit{if}{If}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	586 \node{merge}{Merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	587 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	588 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	589 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	590 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	591 \nodebisplit{store1}{FieldStore x}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	592 \nodebisplit{store2}{FieldStore y}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	593 \nodeframestate{fs1}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	594 \nodeframestate{fs2}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	595 \datalabel{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	596 \datalabel{store2:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	597 \datalabel{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	598 \datalabel{store2:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	599 \control{entry}{if}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	600 \data{if}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	601 \controllabel{if:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	602 \controllabel{if:succ2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	603 \controllabel{store1:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	604 \controllabel{store1:succ2}{fs1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	605 \control{merge}{store2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	606 \controllabel{store2:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	607 \controllabel{store2:succ2}{fs2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	608 \data{cmpnull}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	609 \end{digraphenv}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	610 \caption{Initial graph with the two field stores.}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	611 \label{fig:guard0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	612 \end{figure}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	613
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	614 Figure~\ref{fig:guard1} shows the example graph at a later compilation phase when the field store instructions are lowered to memory store instructions and explicitely modelled null check guards.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	615 The guards are attached to anchor instructions that delimit their possible schedule.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	616 The first guard must not be moved outside the \texttt{if} block; the second guard may be moved before the \texttt{If} instruction, because at this point it is already guaranteed that the second store is executed.
2598 e4395464810e Made graphs smaller. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2597 diff changeset	617
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	618 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	619 \centering
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	620 \begin{digraphenv}{scale=0.5}{guard1}
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	621 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	622 \node{anchor1}{Anchor}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	623 \node{anchor2}{Anchor}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	624 \nodesplit{if}{If}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	625 \node{merge}{Merge}
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	626 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	627 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	628 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	629 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	630 \nodeguard{guard1}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	631 \nodeguard{guard2}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	632 \nodetrisplit{store1}{MemStore 16 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	633 \nodetrisplit{store2}{MemStore 20 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	634 \nodeframestate{fs1}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	635 \nodeframestate{fs2}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	636 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	637 \data{store2:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	638 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	639 \data{store2:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	640 \data{store1:in3}{guard1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	641 \data{store2:in3}{guard2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	642 \data{guard1:in1}{anchor2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	643 \data{guard2:in1}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	644 \data{guard1:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	645 \data{guard2:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	646 \control{entry}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	647 \control{anchor1}{if}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	648 \data{if}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	649 \controllabel{if:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	650 \controllabel{if:succ2}{anchor2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	651 \control{anchor2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	652 \controllabel{store1:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	653 \controllabel{store1:succ2}{fs1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	654 \control{merge}{store2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	655 \controllabel{store2:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	656 \controllabel{store2:succ2}{fs2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	657 \data{cmpnull}{p}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	658 \end{digraphenv}
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	659 \caption{A load guarded by a null check guard.}
15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	660 \label{fig:guard1}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	661 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	662
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	663 The first guard can be easily removed, because it is guarded by an \texttt{If} instruction that checks the same condition.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	664 Therefore we can remove the guard and the anchor from the graph and this gives us the graph shown in Figure \ref{fig:guard2}.
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	665
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	666 There is another optimization for guard instructions: If two guards that are anchored to the true and false branch of the same \texttt{If} instruction have the same condition, they can be merged, so that the resulting guard is anchored at the most distant node of which the \texttt{If} instruction is a postdominator.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	667
2598 e4395464810e Made graphs smaller. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2597 diff changeset	668
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	669 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	670 \centering
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	671 \begin{digraphenv}{scale=0.5}{guard2}
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	672 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	673 \node{anchor1}{Anchor}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	674 \nodesplit{if}{If}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	675 \node{merge}{Merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	676 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	677 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	678 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	679 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	680 \nodeguard{guard2}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	681 \nodetrisplit{store1}{MemStore 16 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	682 \nodetrisplit{store2}{MemStore 20 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	683 \nodeframestate{fs1}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	684 \nodeframestate{fs2}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	685 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	686 \data{store2:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	687 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	688 \data{store2:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	689 \data{store2:in3}{guard2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	690 \data{guard2:in1}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	691 \data{guard2:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	692 \control{entry}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	693 \control{anchor1}{if}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	694 \data{if}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	695 \controllabel{if:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	696 \controllabel{if:succ2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	697 \controllabel{store1:succ1}{merge}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	698 \controllabel{store1:succ2}{fs1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	699 \control{merge}{store2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	700 \controllabel{store2:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	701 \controllabel{store2:succ2}{fs2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	702 \data{cmpnull}{p}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	703 \end{digraphenv}
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	704 \caption{After removing redundant guards.}
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	705 \label{fig:guard2}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	706 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	707
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	708 The remaining guard can now be moved above the \texttt{If} condition and be used to eliminate the need for the \texttt{If} node.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	709 From this point on, the guard can however no longer be moved below the first memory store.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	710 We use a control dependency from the guard to the field store to express this condition.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	711 The link between the second store and the guard and the control flow merge instruction is no longer necessary.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	712
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	713 \begin{figure}[h]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	714 \centering
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	715 \begin{digraphenv}{scale=0.5}{guard3}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	716 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	717 \node{anchor1}{Anchor}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	718 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	719 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	720 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	721 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	722 \nodeguard{guard2}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	723 \nodetrisplit{store1}{MemStore 16 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	724 \nodetrisplit{store2}{MemStore 20 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	725 \nodeframestate{fs1}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	726 \nodeframestate{fs2}{FrameState}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	727 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	728 \data{store2:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	729 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	730 \data{store2:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	731 \data{store2:in3}{guard2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	732 \data{guard2:in1}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	733 \data{guard2:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	734 \control{guard2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	735 \control{entry}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	736 \control{anchor1}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	737 \controllabel{store1:succ2}{fs1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	738 \control{store1}{store2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	739 \controllabel{store2:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	740 \controllabel{store2:succ2}{fs2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	741 \data{cmpnull}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	742 \end{digraphenv}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	743 \caption{After eliminating an if with a guard.}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	744 \label{fig:guard3}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	745 \end{figure}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	746
2679 07aa0a31fffb Rewrote frame state to be not-so-Java-specific. Clarified and reduced the usage of the term "node". Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2678 diff changeset	747 At some point during the compilation, guards need to be fixed, which means that appropriate data and control dependencies will be inserted so that they cannot move outside the scope of the associated frame state.
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	748 This will generate deoptimization-free zones that can be targeted by the most aggressive optimizations.
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	749 A simple algorithm for this removal of frame states would be to move all guards as far upwards as possible and then the guards are fixed using anchor nodes.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	750 In our example, the guard is already fixed, so there is no deoptimization point that uses any of the memory store frame states.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	751 Therefore we can delete the frame states from the graph (see Figure \ref{fig:guard4}).
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	752
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	753 \begin{figure}[h]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	754 \centering
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	755 \begin{digraphenv}{scale=0.5}{guard4}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	756 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	757 \node{anchor1}{Anchor}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	758 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	759 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	760 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	761 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	762 \nodeguard{guard2}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	763 \nodetrisplit{store1}{MemStore 16 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	764 \nodetrisplit{store2}{MemStore 20 (int)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	765 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	766 \data{store2:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	767 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	768 \data{store2:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	769 \data{store2:in3}{guard2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	770 \data{guard2:in1}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	771 \data{guard2:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	772 \control{guard2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	773 \control{entry}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	774 \control{anchor1}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	775 \control{store1}{store2}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	776 \controllabel{store2:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	777 \data{cmpnull}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	778 \end{digraphenv}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	779 \caption{After removing the frame states.}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	780 \label{fig:guard4}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	781 \end{figure}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	782
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	783 Now we can use memory coalescing to combine the two stores without frame state to adjacent locations in the same object.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	784 This is only possible if the first store does not have a frame state.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	785 Figure \ref{fig:guard5} shows the resulting graph.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	786
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	787
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	788 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	789 \centering
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	790 \begin{digraphenv}{scale=0.5}{guard5}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	791 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	792 \node{anchor1}{Anchor}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	793 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	794 \node{cmpnull}{NonNull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	795 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	796 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	797 \nodeguard{guard2}{Guard}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	798 \nodetrisplit{store1}{MemStore 16 (long)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	799 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	800 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	801 \data{guard2:in1}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	802 \data{guard2:in2}{cmpnull}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	803 \control{guard2}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	804 \control{entry}{anchor1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	805 \control{anchor1}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	806 \controllabel{store1:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	807 \data{cmpnull}{p}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	808 \end{digraphenv}
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	809 \caption{After coalescing the two memory stores.}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	810 \label{fig:guard5}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	811 \end{figure}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	812
2682 c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	813 A memory store that immediately follows a null check guard instruction on the same object, can be combined into a store with an implicit null check (that deoptimizes instead of throwing the exception).
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	814 Therefore, we can remove the guard again and also the anchor is no longer necessary.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	815 Figure~\ref{fig:guard6} shows now that fully optimized graph that is generated for Listing~\ref{lst:guard1}.
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	816
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	817 \begin{figure}[h]
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	818 \centering
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	819 \begin{digraphenv}{scale=0.5}{guard6}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	820 \textnode{entry}{Entry}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	821 \node{return}{Return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	822 \textnode{p}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	823 \textnode{const0}{0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	824 \nodetrisplit{store1}{DeoptimizingMemStore 16 (long)}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	825 \data{store1:in1}{p}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	826 \data{store1:in2}{const0}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	827 \control{entry}{store1}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	828 \controllabel{store1:succ1}{return}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	829 \end{digraphenv}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	830 \caption{Fully optimized method.}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	831 \label{fig:guard6}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	832 \end{figure}
c5739b99762a New field store / guard / frame state example. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2679 diff changeset	833
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	834
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	835 \section{Conclusions}
2618 15774da89658 Incorporated comments from Peter. Renamings trap=>guard and guard/split=>anchor. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2604 diff changeset	836 \label{sec:conclusions}
2597 08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	837 This document sketched the strategy for the Graph compiler.
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	838 We already reached M1 (as defined in Section~\ref{sec:mile}) and have the following plans for M2 to M4:
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	839 \begin{description}
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	840 \item[M2:] June 30th, 2011
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	841 \item[M3:] August 15th, 2011
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	842 \item[M4:] September 30th, 2011
08cda6637103 More doc + conclusion. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2591 diff changeset	843 \end{description}
2685 c866126a8df3 typo Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2682 diff changeset	844 After we reach M4, we want to create a new project road map that further improves the Graal compiler with respect to its two main goals: Modularity and peak performance.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	845
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	846 \end{document}

Mercurial > hg > truffle

annotate graal/com.oracle.max.graal.doc.initial/graal_compiler.tex @ 2892:5005a5607506