--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/GraalCompiler/src/com/sun/c1x/graph/package-info.java	Wed Apr 27 11:50:44 2011 +0200
@@ -0,0 +1,153 @@
+/*
+ * Copyright (c) 2010, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * <H2>IR Graph building</H2>
+ *
+ * The {@link com.sun.c1x.graph.IR} class drives the generation of the HIR graph for a method, making use of other
+ * utility classes in this package.
+ *
+ * The graph building is separated into a basic build phase ({@link com.sun.c1x.graph.IR#buildGraph} method)and
+ * (currently) two optimization phases ({@link com.sun.c1x.graph.IR#optimize1} and
+ * {@link com.sun.c1x.graph.IR#optimize2}) although the basic phase also does some (basic) optimizations.
+ *
+ * <H2>Basic Graph Build Phase</H2>
+ *
+ * {@code IR.buildGraph} creates an {@link com.sun.c1x.ir.IRScope topScope} object,
+ * that represents a context for inlining, and then invokes the constructor for the
+ * {@link com.sun.c1x.graph.GraphBuilder} class, passing the {@link com.sun.c1x.C1XCompilation}, and {@code IR}
+ * instances, which are cached. The following support objects are created in the constructor:
+ *
+ * <ul>
+ * <li>{@code memoryMap}: an instance of {@link com.sun.c1x.graph.MemoryMap}
+ * <li>{@code localValueMap}: an instance of {@link com.sun.c1x.opt.ValueMap}
+ * <li>{@code canonicalizer}: an instance of {@link com.sun.c1x.opt.Canonicalizer}
+ * </ul>
+ *
+ * Now the {@link com.sun.c1x.graph.GraphBuilder#build} is invoked with {@code topScope} as argument.
+ *
+ * <H3>{@code GraphBuilder.build}</H3>
+ *
+ * <ol>
+ * <li>The {@link com.sun.c1x.graph.IR#startBlock} field of the cached {@link com.sun.c1x.graph.IR} instance is set to a newly created
+ * {@link com.sun.c1x.ir.BlockBegin} node, with bytecode index 0 and then the {@link com.sun.c1x.graph.BlockMap} is
+ * constructed by calling {@link com.sun.c1x.C1XCompilation#getBlockMap}. This behaves slightly differently depending on
+ * whether this is an OSR compilation. If so, a new {@link com.sun.c1x.ir.BlockBegin} node is added to the map at the OSR bytecode
+ * index. The map is then built by the{@link com.sun.c1x.graph.BlockMap#build}, which takes a boolean argument that
+ * controls whether a second pass is made over the bytecodes to compute stores in loops. This always false for an OSR
+ * compilation (why?). Otherwise, it is only true if enabled by the {@link com.sun.c1x.C1XOptions#PhiLoopStores}
+ * compilation option. FInally some unneeded state from the map is removed by the {@link com.sun.c1x.graph.BlockMap#cleanup} method, and
+ * the statistics are updated.
+ * </li>
+ *
+ * <li>Next the {@link com.sun.c1x.graph.GraphBuilder#pushRootScope} method is called, with the passed-in {@link com.sun.c1x.ir.IRScope}
+ * object, the {@link com.sun.c1x.graph.BlockMap} returned by build and the {@code startBlock}. (Note: Unlike
+ * {@link com.sun.c1x.graph.GraphBuilder#pushScope}, this method does not propagate the
+ * {@link com.sun.c1x.graph.BlockMap#storesInLoops} field to the {@link com.sun.c1x.ir.IRScope} object, which means that
+ * {@link com.sun.c1x.ir.BlockBegin#insertLoopPhis} will always get null for this value. Is this a bug?).
+ * {@link com.sun.c1x.graph.GraphBuilder#pushRootScope} initializes the {@link com.sun.c1x.graph.GraphBuilder#scopeData} field with a
+ * {@link com.sun.c1x.graph.ScopeData} instance, with null parent. The
+ * {@link com.sun.c1x.graph.GraphBuilder#compilation} instance is called to get an {@link com.sun.cri.ri.RiConstantPool}
+ * , which is C1X's interface to constant pool information. The {@link com.sun.c1x.graph.GraphBuilder#curBlock} field is
+ * set to the {@code startBlock}.
+ * <p>
+ *
+ * Now a {@link com.sun.c1x.value.FrameState initialState} object is created by
+ * {@link com.sun.c1x.graph.GraphBuilder#stateAtEntry}. If the method is not static, then a {@link com.sun.c1x.ir.Local}
+ * instance is created at index 0. Since the receiver cannot be {@code null}, the
+ * {@link com.sun.c1x.ir.Value.Flag#NonNull} flag is set. Additional {@link com.sun.c1x.ir.Local} instances are created for the
+ * arguments to the method. The index is incremented by the number of slots occupied by the
+ * {@link com.sun.cri.ci.CiKind} corresponding to the argument type. All the {@link com.sun.c1x.ir.Local} instances are stored in the
+ * {@link com.sun.c1x.value.FrameState} using the {@link com.sun.c1x.value.FrameState#storeLocal} method. This {@link com.sun.c1x.value.FrameState} is then
+ * merged into the {@link com.sun.c1x.ir.BlockBegin#stateBefore} for the {@code startBlock}, which just results in a
+ * copy since {@code stateBefore} will be {@code null}.
+ * </li>
+ * <li>
+ * This step sets up three instance fields: {@link com.sun.c1x.graph.GraphBuilder#curBlock} and
+ * {@link com.sun.c1x.graph.GraphBuilder#lastInstr} to {@code startBlock} and
+ * {@link com.sun.c1x.graph.GraphBuilder#curState} to {@code initialState}. (N.B. the setting of {@code curBlock} is
+ * redundant as it is done in {@link com.sun.c1x.graph.GraphBuilder#pushRootScope}).
+ * </li>
+ * <li>
+ * Step 4 contains special handling for synchronized methods (TBD), otherwise it calls
+ * {@link com.sun.c1x.graph.GraphBuilder#finishStartBlock} which adds a {@link com.sun.c1x.ir.Base} block as the end of
+ * the {@code startBlock}. The {@link com.sun.c1x.ir.Base} block has one successor set to the (entry) block with flag
+ * {@link com.sun.c1x.ir.BlockBegin.BlockFlag#StandardEntry}, that was created by {@link com.sun.c1x.graph.BlockMap#build} (and possibly a
+ * successor to an OSREntry block).
+ * </li>
+ * <li>
+ * Then the {@link com.sun.c1x.ir.IRScope#lockStackSize} is computed. (TBD)
+ * </li>
+ * <li>
+ * Then the method is checked for being intrinsic, i.e., one that has a hard-wired implementation known to C1X. If so,
+ * and {@link com.sun.c1x.C1XOptions#OptIntrinsify} is set, an attempt is made to inline it (TBD). Otherwise, or if the
+ * intrinsification fails, normal processing continues by adding the entry block to the
+ * {@link com.sun.c1x.graph.ScopeData} work list (kept topologically sorted) and calling
+ * {@link com.sun.c1x.graph.GraphBuilder#iterateAllBlocks}.
+ * </li>
+ * <li>
+ * Finally there is some cleanup code for synchronized blocks and OSR compilations.
+ * </li>
+ * </ol>
+ *
+ * <H3>{@link com.sun.c1x.graph.GraphBuilder#iterateAllBlocks}</H3>
+ * {@link com.sun.c1x.graph#iterateAllBlocks} repeatedly removes a block from the work list and, if not already visited, marks it so,
+ * kills the current memory map, sets {@link com.sun.c1x.graph.GraphBuilder#curBlock}, {@link com.sun.c1x.graph.GraphBuilder#curState} and {@link com.sun.c1x.graph.GraphBuilder#lastInstr} and then calls
+ * {@link com.sun.c1x.graph.GraphBuilder#iterateBytecodesForBlock}.
+ *
+ * This process continues until all the blocks have been visited (processed) after which control returns to {@code
+ * build}.
+ * <p>
+
+ * <H3>{@link com.sun.c1x.graph.GraphBuilder#iterateBytecodesForBlock}</H3>
+ *
+ * {@link com.sun.c1x.graph.GraphBuilder#iterateBytecodesForBlock} performs an abstract interpretation of the bytecodes in the block, appending new
+ * nodes as necessary, until the last added node is an instance of {@link com.sun.c1x.ir.BlockEnd}. (Note: It has an
+ * explicit check for finding a new {@link com.sun.c1x.ir.BlockBegin} before a {@link com.sun.c1x.ir.BlockEnd} but
+ * {@link com.sun.c1x.graph.BlockMap#moveSuccessorLists} has a similar check so this may be redundant). For example,
+ * consider the following bytecodes:
+ *
+ * <pre>
+ * <code>
+ *         0: iconst_0
+ *         1: istore_2
+ *         2: goto 22
+ * </code>
+ * </pre>
+ *
+ * The {@code iconst_0} bytecode causes a {@link com.sun.c1x.ir.Constant} node representing zero to be pushed on the
+ * {@link com.sun.c1x.graph.GraphBuilder#curState} stack and the node to be appended to the {@link com.sun.c1x.ir.BlockBegin} (entry) node associated with index 0.
+ * The {@code istore_2} causes the node to be popped of the stack and stored in the local slot 2. No IR node is
+ * generated for the {@code istore_2}. The {@code goto} creates a {@link com.sun.c1x.ir.Goto} node which is a subclass
+ * of {@link com.sun.c1x.ir.BlockEnd}, so this terminates the iteration. As part of termination the {@link com.sun.c1x.ir.Goto} node is marked as the
+ * end node of the current block and the {@link com.sun.c1x.value.FrameState} is propagated to the successor node(s) by merging any
+ * existing {@link com.sun.c1x.value.FrameState} with the current state. If the target is a loop header node this involves inserting
+ * {@link com.sun.c1x.ir.Phi} nodes. Finally, the target node is added to the {@code scopeData} work list.
+ * <p>
+ *
+ *
+ * @author Ben Titzer
+ * @author Mick Jordan
+ *
+ */
+package com.sun.c1x.graph;