truffle: doc/design/graal_compiler.tex annotate

annotate doc/design/graal_compiler.tex @ 2588:26ecba0ead6d

Update on doc.

author	Thomas Wuerthinger <thomas@wuerthinger.net>
date	Thu, 05 May 2011 13:59:43 +0200
parents	999407dbfe10
children	795df30f979d

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}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	2 \usepackage[pdftex]{graphicx}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	3 \usepackage{environ}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	4 \usepackage{amsmath}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	5 \usepackage{amsfonts}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	6 \usepackage[english]{babel}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	7 \usepackage[utf8]{inputenc}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	8 \usepackage{lmodern}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	9 \usepackage[T1]{fontenc}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	10 \usepackage{color}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	11
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	12 \input{graphdrawing}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	13
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	14 \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	15
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	16 \newcommand{\Sa}{{\Large$^*$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	17 \newcommand{\Sb}{{\Large$^\dag$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	18 \newcommand{\Sc}{{\Large$^\S$}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	19
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	20
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	21 \newcommand{\mynote}[2]{
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	22 \textcolor{red}{\fbox{\bfseries\sffamily\scriptsize#1}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	23 {\small\textsf{\emph{#2}}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	24 \fbox{\bfseries\sffamily\scriptsize }}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	25
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	26 \newcommand\TODO[1]{\mynote{TODO}{#1}}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	27 \newcommand\cw[1]{\mynote{CW}{#1}}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	28 \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	29 \newcommand\nodename[1]{\texttt{#1}}
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	30
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	31
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	32
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	33 \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	34
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	35 \journalname{Graal Compiler Design}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	36 \def\makeheadbox{{%
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	37 \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	38 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	39 \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	40 \kern3pt}\hfil\kern3pt\vrule}\hrule}%
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	41 \hss}}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	42
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	43 \begin{document}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	44
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	45 \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	46 \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	47
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	48 \date{Created: \today}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	49
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	50 \title{The Graal Compiler}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	51 \subtitle{Design and Strategy \\ \textcolor{red}{work in progress}}
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	52
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	53 \maketitle
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	54
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	55 \abstract{
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	56 The Graal compiler aims at improving C1X, the Java port of the HotSpot client compiler, both in terms of modularity and peak performance.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	57 The compiler should work with the Maxine VM and the HotSpot VM.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	58 This document contains information about the proposed design and strategy for developing the Graal compiler.}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	59
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	60 \section{Context}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	61
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	62 In 2009, the Maxine team started with creating C1X, a Java port of the HotSpot client compiler, and integrate it into the Maxine VM.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	63 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 that enables the use of one compiler for multiple VMs.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	64 In June 2010, we started integrating C1X into the HotSpot VM and we called the resulting system Graal~VM.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	65 Currently, the Graal~VM is fully functional and runs benchmarks (SciMark, DaCapo) at a similar speed to the HotSpot client compiler.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	66
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	67 \section{Goals}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	68 The Graal compiler effort aims at rewriting the high-level intermediate representation of C1X with two main goals:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	69 \begin{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	70 \item[Modularity:] A modular design of the compiler should simplify the implementation of new languages, new back-ends, and new optimizations.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	71 \item[Peak Performance:] A more powerful intermediate representation should enable the implementation of heavy-weight optimizations that impact the peak performance of the resulting machine code.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	72 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	73
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	74 \section{Design}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	75 For the implementation of the Graal compiler, we rely on the following design decisions:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	76 \begin{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	77 \item[Graph Representation:]
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	78 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	79 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	80 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	81 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	82 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	83 The graph does not allow data flow edge cycles or control flow edge cycles.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	84 We achieve this by explicitely modelling loops (see Section~\ref{sec:loops}).
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	85 \item[Extensibility:]
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	86 The compiler is extensible by adding new compiler phases and new node subclasses without modifying the compiler's sources.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	87 A node has an abstract way of expressing its effect 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	88 We use the ``everything is an extension'' concept.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	89 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	90 \item[Detailing:]
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	91 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	92 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	93 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	94 \item[Generality:]
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	95 The compiler does not require Java as its input.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	96 This is achieved by having a graph as the starting point of the compilation and not a Java bytecodes array.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	97 Building the graph from the Java bytecodes must happen before giving a method to the compiler.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	98 This enables front-ends for different languages (e.g., Ruby) to provide their own graph.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	99 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	100 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	101
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	102 \section{Milestones}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	103 The Graal compiler is developed starting from the current C1X source code base.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	104 This helps us testing the compiler at every intermediate development step on a variety of Java benchmarks.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	105 We define the following development milestones and when they are considered achieved:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	106 \begin{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	107 \item[M1:] We have a fully working Graal VM version with a stripped down C1X compiler that does not perform any optimizations.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	108 \item[M2:] We modified the high-level intermediate representation to be based on the Graal compiler graph data structure.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	109 \item[M3:] We have reimplemented and reenabled compiler optimizations in the Graal compiler that previously existed in C1X.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	110 \item[M4:] We have reintegrated the new Graal compiler into the Maxine VM and can use it as a Maxine VM bootstrapping compiler.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	111 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	112
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	113 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	114 \begin{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	115 \item Removal of the XIR template mechanism and replacement with a snippet mechanism that works with the Graal compiler graph.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	116 \item Improvements for Graal peak performance (loop optimizations, escape analysis, bounds check elimination, processing additional interpreter runtime feedback).
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	117 \item Implementation of a prototype front-end for different languages, e.g., JavaScript.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	118 \end{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	119
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	120 \section{Implementation}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	121
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	122 \subsection{Loops}
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	123 \label{sec:loops}
2573 6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	124 Loops form a first-class construct in the IR that is expressed in specialized IR nodes during all optimization phases.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	125 We only compile methods with a control flow where every loop has only one single entry point.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	126 This entry point is a \nodename{LoopBegin} node.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	127 This node is connected to a \nodename{LoopEnd} node that merges all control flow paths that do not exit the loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	128 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	129 It goes from the beginning to the end in order to make the graph acyclic.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	130 An algorithm that traverses the control flow has to explicitely decide whether it wants to incorporate backedges (i.e., special case the treatment of \nodename{LoopEnd}) or ignore them.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	131 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	132
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	133 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	134 \label{fig:loop1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	135 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	136 \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	137 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	138 \textnode{Exit1}{First loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	139 \textnode{Exit2}{Second loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	140 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	141 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	142 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	143 \nodesplit{If2}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	144 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	145 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	146 \controllabel{If1:succ1}{If2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	147 \controllabel{If2:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	148 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	149 \controllabel{If1:succ2}{Exit1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	150 \controllabel{If2:succ2}{Exit2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	151 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	152 \caption{A simple loop with two exits.}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	153 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	154
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	155 \subsection{Loop Phis}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	156 Data flow in loops is modelled with special phi nodes at the beginning and the end of the loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	157 The \nodename{LoopEnd} node merges every value that is flows into the next loop iteration in associated \nodename{LoopEndPhi} nodes.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	158 A corresponding \nodename{LoopBeginPhi} node that is associated with the loop header has a control flow dependency on the \nodename{LoopEndPhi} node.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	159 Figure \ref{fig:loop2} shows how a simple counting loop is modelled in the graph.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	160
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	161 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	162 \label{fig:loop2}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	163 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	164 \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	165 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	166 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	167 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	168 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	169 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	170 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	171 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	172 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	173 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	174 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	175 \nodebi{Compare}{<}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	176 \nodebi{LoopBeginPhi}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	177 \nodebi{Add}{+}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	178 \datalabel{Add:in1}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	179 \datalabel{Add:in2}{Constant1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	180 \nodebi{LoopEndPhi}{LoopEndPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	181 \control{LoopBeginPhi}{LoopEndPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	182 \data{LoopEndPhi:in1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	183 \data{LoopEndPhi:in2}{Add}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	184 \datalabel{LoopBeginPhi:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	185 \datalabel{LoopBeginPhi:in2}{Constant0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	186 \datalabel{Compare:in1}{LoopBeginPhi}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	187 \datalabel{Compare:in2}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	188 \data{If1}{Compare}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	189 \controllabel{If1:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	190 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	191 \controllabel{If1:succ2}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	192 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	193 \caption{Graal compiler graph for a loop counting from 0 to n-1.}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	194 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	195
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	196 \subsection{Loop Counters}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	197 The compiler is capable of recognizing variables that are only increased within a loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	198 A potential overflow of such a variable is guarded with a trap before the loop.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	199 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	200
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	201
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	202 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	203 \label{fig:loop3}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	204 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	205 \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	206 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	207 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	208 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	209 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	210 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	211 \nodesplit{LoopBegin}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	212 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	213 \nodesplit{If1}{If}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	214 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	215 \controllabel{LoopBegin:succ2}{If1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	216 \nodebi{Compare}{<}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	217 \nodetri{LoopCounter}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	218 \datalabel{LoopCounter:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	219 \datalabeltext{LoopCounter:in2}{Constant0}{init}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	220 \datalabeltext{LoopCounter:in3}{Constant1}{stride}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	221 \datalabel{Compare:in1}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	222 \datalabel{Compare:in2}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	223 \data{If1}{Compare}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	224 \controllabel{If1:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	225 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	226 \controllabel{If1:succ2}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	227 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	228 \caption{Graal compiler graph after loop counter transformation.}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	229 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	230
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	231 \subsection{Bounded Loops}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	232
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	233 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	234 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.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	235 If the totel number of iterations is reached, the loop is exited directly from the loop header.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	236 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	237 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	238
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	239 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	240 \label{fig:loop4}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	241 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	242 \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	243 \textnode{BeforeLoop}{Loop entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	244 \textnode{Exit}{Loop exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	245 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	246 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	247 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	248 \nodesplittri{LoopBegin}{BoundedLoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	249 \node{LoopEnd}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	250 \controllabel{LoopBegin:succ1}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	251 \controllabel{LoopBegin:succ2}{LoopEnd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	252 \controllabel{LoopBegin:succ3}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	253 \nodetri{LoopCounter}{LoopCounter}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	254 \datalabel{LoopCounter:in1}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	255 \datalabeltext{LoopCounter:in2}{Constant0}{init}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	256 \datalabeltext{LoopCounter:in3}{Constant1}{stride}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	257 \data{LoopBegin}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	258 \controllabel{BeforeLoop}{LoopBegin}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	259 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	260 \caption{Graal compiler graph after bounded loop transformation.}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	261 \end{figure}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	262
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	263 \subsection{Vectorization}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	264
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	265 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	266 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	267 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	268 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	269 Figure \ref{fig:loop5} shows the compiler graph of the example loop after vectorization.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	270 The vector nodes all work on an ordered list of integer values and are subject to canonicalization like any other node.
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	271
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	272
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	273 \begin{figure}[h]
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	274 \label{fig:loop5}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	275 \centering
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	276 \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	277 \textnode{Entry}{Entry}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	278 \textnode{Exit}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	279 \textnode{n}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	280 \textnode{Constant0}{0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	281 \textnode{Constant1}{1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	282 \node{Vector}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	283 \nodebi{VectorAdd}{VectorAdd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	284 \nodebi{VectorMul}{VectorMul}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	285 \control{Entry}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	286 \control{Vector}{Exit}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	287 \datalabel{VectorAdd:in1}{Vector}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	288 \datalabel{VectorAdd:in2}{Constant0}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	289 \datalabel{VectorMul:in1}{VectorAdd}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	290 \datalabel{VectorMul:in2}{Constant1}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	291 \data{Vector}{n}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	292 \end{digraphenv}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	293 \caption{Graal compiler graph after bounded loop transformation.}
6d99b909696d Documentation: More content and graphs on loops and vectorization. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2572 diff changeset	294 \end{figure}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	295
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	296 \subsection{Project Source Structure}
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	297 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.graal}).
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	298
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	299 \begin{description}
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	300 \item[graph] contains the abstract node implementation, the graph implementation and all the associated tools and auxiliary classes.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	301 \item[nodes] contains the implementation of known basic nodes (e.g., phi nodes, control flow nodes, \ldots).
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	302 Additional node classes should go into seperate projects and be specializations of the known basic nodes.]
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	303 \item[java] contains code for building graphs from Java bytecodes and Java-specific nodes.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	304 \item[opt] contains optimizations such as global value numbering or conditional constant propagation.
26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	305 \item[compiler] contains the compiler, including:
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	306 \begin{itemize}
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	307 \item Schedules the compilation phases.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	308 \item Implementation of the \emph{compiler interface} (CI).
2588 26ecba0ead6d Update on doc. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2578 diff changeset	309 \item Implements the final compilation phase that produces the low-level representation.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	310 \item Machine code creation, including debug info.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	311 \end{itemize}
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	312 \cw{So you want to keep the backend as part of the ``main compiler'' at first. Seems OK for me.}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	313 \end{description}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	314
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	315 \subsection{Nodes and Graphs}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	316 The most important aspect of a compiler is the data structure that holds information about an executable piece of code, called \emph{intermediate representation}~(IR).
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	317 The IR used in the Graal Compiler (simply referred to as \emph{the compiler} in the rest of this document) was designed in such a way as to allow for extensive optimizations, easy traversal, compact storage and efficient processing.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	318
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	319 \subsubsection{The Graph Data Structure}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	320 \begin{itemize}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	321 \item A graph deals out ids for new nodes and can be queried for the node corresponding to a given id.
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	322 \item Graphs can manage side data structures, which will be automatically invalidated and lazily recomputed whenever the graph changes. Examples for side data structures are dominator trees and temporary schedules. These side data structures will usually be understood by more than one optimization.
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	323 \end{itemize}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	324
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	325 \subsubsection{The Node Data Structure}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	326 \begin{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	327 \item Each node is always associated with a graph.
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	328 \item Each node has an immutable id which is unique within its associated graph. \cw{The server compiler supports ``renumbering'' of nodes to make the ids dense again after large graph manipulations that deleted many nodes.}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	329 \item Nodes represent either operations on values or control flow operations.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	330 \item Nodes can have a data dependency, which means that one node requires the result of some other 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.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	331 \item Nodes can have a control flow dependency, which means that the execution of one node depends on some other node. This includes conditional execution, memory access serialization and other reasons, and again introduces a partial order to the set of nodes.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	332 \item Nodes can only have data and control dependencies to nodes which belong to the same graph.
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	333 \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. Situations that are normally incur cycles (like loops) are represented by special nodes (like LoopEnd).
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	334 \cw{I don't like that item. Cycles are a normal thing for control flow and for phi functions. I would phrase it as something like that: Nodes can only have data and control dependencies to nodes that are dominators. The only exception of that are control loop headers and phi functions}
0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	335 \item Ordering between nodes is specified only to the extent which is required to correctly express the semantics of a given program. Some compilers (notably the HotSpot client compiler \cw{Wrong: the client compiler only has a fixed order of pinned instructions, most instructions are not pinned and can be moved around freely}) always maintain a complete order for all nodes (called \emph{scheduling}), which impedes advanced optimizations. For algorithms that require a fixed ordering of nodes, a temporary schedule can always be generated.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	336 \item Both data and control dependencies can be traversed in both directions, so that each node can be traversed in four directions:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	337 \begin{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	338 \item \emph{inputs} are all nodes that this node has data dependencies on.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	339 \item \emph{usages} are all nodes that have data dependencies on this node, this is regarded as the inverse of inputs.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	340 \item \emph{successors} are all nodes that have a control dependency on this node.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	341 \item \emph{predecessors} are all nodes that this node has control dependencies on, this is regarded as the inverse of successors.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	342 \end{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	343 \item Only inputs and successors can be changed, and changes to them will update the usages and predecessors.
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	344 \item The Node class needs to provide facilities for subclasses to perform actions upon cloning, dependency changes, etc.
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	345 \item Nodes cannot be reassigned to another graph, they are cloned instead \cw{Why should there be the need for more than one graph when compiling a method?}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	346 \end{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	347
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	348 \subsection{Frame States}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	349 Frame states capture the state of the program, in terms of the source representation (e.g., Java state: local variables, expressions, ...).
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	350 Whenever a safepoint is reached or \cw{why is that an ``or'', both is basically the same} \ls{uncommon traps can be introduced at other points, e.g., at an if branch that isn't compiled} a deoptimization is needed a valid frame state needs to be available.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	351 A frame state is valid as long as the program performs only actions that can safely be reexecuted (e.g., operations on local variables, loads, etc.).
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	352 Thus, frame states need only be generated for bytecodes that cannot be reexecuted:
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	353
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	354 \begin{itemize}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	355 \item Array stores: {\tt IASTORE, LASTORE, FASTORE, \\DASTORE, AASTORE, BASTORE, CASTORE, SASTORE}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	356 \item Field stores: {\tt PUTSTATIC, PUTFIELD}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	357 \item Method calls: {\tt INVOKEVIRTUAL, INVOKESPECIAL, \\INVOKESTATIC, INVOKEINTERFACE}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	358 \item Synchronization: {\tt MONITORENTER, MONITOREXIT}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	359 \end{itemize}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	360
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	361 Within the node graph a frame state is represented as a node that is fixed to the node that caused it to be generated (control dependency).
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	362
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	363
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	364 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	365 \label{fig:fs1}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	366 \centering
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	367 \begin{digraphenv}{scale=0.5}{fs1}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	368 \nodetrisplit{store1}{ArrayStore}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	369 \nodebi{load1}{ArrayLoad}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	370 \controllabel{store1:succ1}{load1}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	371 \nodetrisplit{store2}{ArrayStore}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	372 \control{load1}{store2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	373 end [shape=plaintext, label="...", width="2.0"]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	374 store2:succ1:s -> end:n [color=red];
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	375 %
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	376 \nodeframestate{fs1}{FrameState}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	377 \controllabel{store1:succ2}{fs1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	378 \nodeframestate{fs2}{FrameState}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	379 \controllabel{store2:succ2}{fs2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	380 \end{digraphenv}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	381 \caption{Simple example using two frame states.}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	382 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	383
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	384 FrameStates also have data dependencies on the contents of the state: the local variables and the expression stack.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	385
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	386 \subsection{Deoptimization and Uncommon Traps}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	387 Uncommon trap nodes are not fixed to a certain frame state node, they can move around freely and will always use the correct frame state.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	388 The node that is guarded by the deoptimization has a data dependency on the trap, and the trap in turn has a data dependency on the condition and on the most distant node that is postdominated by the guarded node.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	389
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	390 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	391 \label{fig:trap1}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	392 \centering
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	393 \begin{digraphenv}{scale=0.5}{trap1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	394 \nodesplit{if}{If}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	395 \node{split1}{Split}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	396 \controllabel{if:succ1}{split1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	397 nop [shape=plaintext, label="..."]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	398 \control{split1}{nop}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	399 %
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	400 \node{split2}{Split}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	401 \controllabel{if:succ2}{split2}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	402 \nodebi{load1}{MemLoad}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	403 \control{split2}{load1}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	404 \nodebi{load2}{MemLoad}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	405 \control{load1}{load2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	406 \control{load2}{merge}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	407 \node{merge}{Merge}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	408 \control{nop}{merge}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	409 %
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	410 \nodeconst{o1}{obj1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	411 \nodeconst{o2}{obj2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	412 \datalabel{load1:in2}{o1}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	413 \datalabel{load2:in2}{o2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	414 \nodetrap{trap}{Trap}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	415 \node{cmpnull}{IsNull}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	416 \data{cmpnull}{o2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	417 \datalabel{trap:in2}{cmpnull}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	418 \datalabel{load2:in1}{trap}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	419 \datalabel{trap:in1}{split2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	420 \end{digraphenv}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	421 \caption{In this example, the second load is guarded by an uncommon trap, because its receiver might be null (the receiver of the load is assumed to be non-null).
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	422 The trap is anchored to the control split, because as soon as this node is executed the second load must be executed as well.
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	423 In the final scheduling the trap can be placed before or after the first load.}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	424 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	425
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	426 Another type of uncommon trap is a guard, which is used to remove branches that have a very low execution frequency from the compiled code.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	427
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	428 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	429 \label{fig:trap2}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	430 \centering
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	431 \begin{digraphenv}{scale=0.5}{trap2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	432 start [shape=plaintext, label="..."]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	433 start2 [shape=plaintext, label=""]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	434 start3 [shape=plaintext, label=""]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	435 \control{start}{guard}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	436 \node{guard}{Guard}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	437 \nodebi{load1}{MemLoad}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	438 \control{guard}{load1}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	439 \control{load1}{nop}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	440 nop [shape=plaintext, label="..."]
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	441 %
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	442 \nodetrap{trap}{Trap}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	443 \datalabel{trap:in1}{start2}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	444 \datalabel{trap:in2}{start3}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	445 \data{guard}{trap}
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	446 \end{digraphenv}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	447 \caption{In this example the If from the previous example was replaced by a guard and an uncommon trap.
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	448 The guard takes the place of the If in the control flow, and is connected to the trap node.
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	449 The uncommon trap is now anchored to the most distant node of which the If was a postdominator.}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	450 \end{figure}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	451
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	452 At some point during the compilation, trap nodes 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.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	453 This will generate deoptimization-free zones that can be targeted by the most aggressive optimizations.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	454 A simple algorithm for this removal of FrameStates would be to move all traps as far upwards as possible.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	455
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	456
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	457 Multiple Traps with the same condition and anchor can be merged:
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	458
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	459 \begin{figure}[h]
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	460 \label{fig:trap3}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	461 \centering
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	462 \begin{digraphenv}{scale=0.5}{trap3}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	463 \nodesplit{if}{If}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	464 \node{split1}{Split}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	465 \controllabel{if:succ1}{split1}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	466 nop [shape=plaintext, label="..."]
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	467 \control{split1}{nop}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	468 %
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	469 \node{split2}{Split}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	470 \controllabel{if:succ2}{split2}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	471 \nodebi{load1}{MemLoad}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	472 \control{split2}{load1}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	473 \nodebi{load2}{MemLoad}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	474 \control{load1}{load2}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	475 \control{load2}{merge}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	476 \node{merge}{Merge}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	477 \control{nop}{merge}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	478 %
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	479 \nodeconst{o}{obj}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	480 \datalabel{load1:in2}{o}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	481 \datalabel{load2:in2}{o}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	482 \nodetrap{trap}{Trap}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	483 \node{cmpnull}{IsNull}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	484 \data{cmpnull}{o}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	485 \datalabel{trap:in2}{cmpnull}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	486 \datalabel{load2:in1}{trap}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	487 \datalabel{load1:in1}{trap}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	488 \datalabel{trap:in1}{split2}
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	489 \end{digraphenv}
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	490 \caption{Two loads guarded by the same Trap.}
999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	491 \end{figure}
2577 ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	492
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	493 Also, if two Traps that are anchored to the true and false branch of the same If have the same condition, they can be merged, so that the resulting Trap is anchored at the most distant node of which the If is a postdominator.
ac2029d0898f doc: framestate and deopt changes Lukas Stadler <lukas.stadler@jku.at> parents: 2576 diff changeset	494
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	495 %Frame states should be represented using a delta-encoding.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	496 %This will make them significantly smaller and will make inlining, etc. much easier.
c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	497 %In later compilation phases unnecessary frame states might be removed, using a mark-and-merge algorithm.
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	498
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	499 \subsection{Graph Building}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	500 \begin{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	501 \item The graph built by the initial parser (called \emph{GraphBuilder}) should be as close to the source representation (bytecode, ...) as possible.
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	502 \item All nodes should be able to immediately lower themselves to a machine-level representation. \cw{What is that? You mean every node has x86 specific code that spits out machine code? Hope you are joking...} This allows for easier compiler development, and also leads to a compiler that is very flexible in the amount of optimizations it performs (e.g. recompilation of methods with more aggressive optimizations).
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	503 \end{itemize}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	504
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	505 \subsection{Graphical Representation}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	506 The graphs in this document use the following node layout:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	507
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	508 \begin{digraphenv}{scale=0.5}{graphrep1}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	509 \node{node1}{nop}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	510 \nodebi{node2}{+}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	511 \nodetri{node3}{phi}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	512 \nodesplit{node4}{if}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	513 \end{digraphenv}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	514
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	515 \cw{That doesn't compile with my latex. What do I have to do to get it working?}
2576 c59db1f02893 doc: expanded framestate section Lukas Stadler <lukas.stadler@jku.at> parents: 2569 diff changeset	516 \ls{graphviz needs to be installed, and pdflatex needs to be started with -shell-escape}
2562 0023bd42eefe comments christian.wimmer@oracle.com parents: 2561 diff changeset	517
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	518 Red arrows always represents control dependencies, while black arrows represent data dependencies:
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	519
2578 999407dbfe10 merge Lukas Stadler <lukas.stadler@jku.at> parents: 2577 2574 diff changeset	520 \begin{digraphenv}{scale=0.5}{graphrep2}
2561 765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	521 \node{a}{a}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	522 \node{b}{b}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	523 \nodesplit{if}{if}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	524 \node{nop}{nop}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	525 \nodebi{add}{+}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	526 \controllabel{if:succ1}{nop}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	527 \controllabel{if:succ2}{add}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	528 \datalabel{add:in1}{a}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	529 \datalabel{add:in2}{b}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	530 \end{digraphenv}
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	531
765dd54244a6 Updated doc. Added Texclipse project. Thomas Wuerthinger <thomas@wuerthinger.net> parents: 2517 diff changeset	532
2517 8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	533
8c6e31c62fba added initial version of design docs, fixed .hgignore (regex, . -> \.) Lukas Stadler <lukas.stadler@jku.at> parents: diff changeset	534 \end{document}

Mercurial > hg > truffle

annotate doc/design/graal_compiler.tex @ 2588:26ecba0ead6d