Mercurial > hg > graal-compiler
view graal/GraalCompiler/src/com/sun/c1x/ir/ComputeLinearScanOrder.java @ 2812:d27bdbec3d67
Removed ArrayLength from CFG. Fixed an issue when scheduling Merge instructions within a block.
If a block only consists of a single Merge instruction, we have to schedule this instruction as the first instruction.
author | Thomas Wuerthinger <thomas@wuerthinger.net> |
---|---|
date | Mon, 30 May 2011 15:24:26 +0200 |
parents | df4c5254c5cc |
children | 775c31be565c |
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/* * Copyright (c) 2009, 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. */ package com.sun.c1x.ir; import java.util.*; import com.sun.c1x.*; import com.sun.c1x.debug.*; import com.sun.c1x.lir.*; import com.sun.c1x.util.*; import com.sun.cri.ci.*; public final class ComputeLinearScanOrder { private final int maxBlockId; // the highest blockId of a block private int numBlocks; // total number of blocks (smaller than maxBlockId) private int numLoops; // total number of loops private boolean iterativeDominators; // method requires iterative computation of dominators List<LIRBlock> linearScanOrder; // the resulting list of blocks in correct order final CiBitMap visitedBlocks; // used for recursive processing of blocks final CiBitMap activeBlocks; // used for recursive processing of blocks final CiBitMap dominatorBlocks; // temporary BitMap used for computation of dominator final int[] forwardBranches; // number of incoming forward branches for each block final List<LIRBlock> loopEndBlocks; // list of all loop end blocks collected during countEdges BitMap2D loopMap; // two-dimensional bit set: a bit is set if a block is contained in a loop final List<LIRBlock> workList; // temporary list (used in markLoops and computeOrder) // accessors for visitedBlocks and activeBlocks void initVisited() { activeBlocks.clearAll(); visitedBlocks.clearAll(); } boolean isVisited(LIRBlock b) { return visitedBlocks.get(b.blockID()); } boolean isActive(LIRBlock b) { return activeBlocks.get(b.blockID()); } void setVisited(LIRBlock b) { assert !isVisited(b) : "already set"; visitedBlocks.set(b.blockID()); } void setActive(LIRBlock b) { assert !isActive(b) : "already set"; activeBlocks.set(b.blockID()); } void clearActive(LIRBlock b) { assert isActive(b) : "not already"; activeBlocks.clear(b.blockID()); } // accessors for forwardBranches void incForwardBranches(LIRBlock b) { forwardBranches[b.blockID()]++; } int decForwardBranches(LIRBlock b) { return --forwardBranches[b.blockID()]; } // accessors for loopMap boolean isBlockInLoop(int loopIdx, LIRBlock b) { return loopMap.at(loopIdx, b.blockID()); } void setBlockInLoop(int loopIdx, LIRBlock b) { loopMap.setBit(loopIdx, b.blockID()); } void clearBlockInLoop(int loopIdx, int blockId) { loopMap.clearBit(loopIdx, blockId); } // accessors for final result public List<LIRBlock> linearScanOrder() { return linearScanOrder; } public int numLoops() { return numLoops; } public ComputeLinearScanOrder(int maxBlockId, LIRBlock startBlock) { this.maxBlockId = maxBlockId; visitedBlocks = new CiBitMap(maxBlockId); activeBlocks = new CiBitMap(maxBlockId); dominatorBlocks = new CiBitMap(maxBlockId); forwardBranches = new int[maxBlockId]; loopEndBlocks = new ArrayList<LIRBlock>(8); workList = new ArrayList<LIRBlock>(8); splitCriticalEdges(); countEdges(startBlock, null); if (numLoops > 0) { markLoops(); clearNonNaturalLoops(startBlock); assignLoopDepth(startBlock); } computeOrder(startBlock); printBlocks(); assert verify(); } void splitCriticalEdges() { // TODO: move critical edge splitting from IR to here } /** * Traverses the CFG to analyze block and edge info. The analysis performed is: * * 1. Count of total number of blocks. * 2. Count of all incoming edges and backward incoming edges. * 3. Number loop header blocks. * 4. Create a list with all loop end blocks. */ void countEdges(LIRBlock cur, LIRBlock parent) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("Counting edges for block B%d%s", cur.blockID(), parent == null ? "" : " coming from B" + parent.blockID()); } if (isActive(cur)) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("backward branch"); } assert isVisited(cur) : "block must be visited when block is active"; assert parent != null : "must have parent"; cur.setLinearScanLoopHeader(); cur.setBackwardBranchTarget(true); parent.setLinearScanLoopEnd(); // When a loop header is also the start of an exception handler, then the backward branch is // an exception edge. Because such edges are usually critical edges which cannot be split, the // loop must be excluded here from processing. if (cur.isExceptionEntry()) { // Make sure that dominators are correct in this weird situation iterativeDominators = true; return; } // assert parent.numberOfSux() == 1 && parent.suxAt(0) == cur : "loop end blocks must have one successor (critical edges are split)"; loopEndBlocks.add(parent); return; } // increment number of incoming forward branches incForwardBranches(cur); if (isVisited(cur)) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("block already visited"); } return; } numBlocks++; setVisited(cur); setActive(cur); // recursive call for all successors int i; for (i = cur.numberOfSux() - 1; i >= 0; i--) { countEdges(cur.suxAt(i), cur); } for (LIRBlock ex : cur.getExceptionHandlerSuccessors()) { countEdges(ex, cur); } clearActive(cur); // Each loop has a unique number. // When multiple loops are nested, assignLoopDepth assumes that the // innermost loop has the lowest number. This is guaranteed by setting // the loop number after the recursive calls for the successors above // have returned. if (cur.isLinearScanLoopHeader()) { assert cur.loopIndex() == -1 : "cannot set loop-index twice"; if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("Block B%d is loop header of loop %d", cur.blockID(), numLoops); } cur.setLoopIndex(numLoops); numLoops++; } if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("Finished counting edges for block B%d", cur.blockID()); } } void markLoops() { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("----- marking loops"); } loopMap = new BitMap2D(numLoops, maxBlockId); for (int i = loopEndBlocks.size() - 1; i >= 0; i--) { LIRBlock loopEnd = loopEndBlocks.get(i); LIRBlock loopStart = loopEnd.suxAt(0); int loopIdx = loopStart.loopIndex(); if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("Processing loop from B%d to B%d (loop %d):", loopStart.blockID(), loopEnd.blockID(), loopIdx); } assert loopEnd.isLinearScanLoopEnd() : "loop end flag must be set"; // assert loopEnd.numberOfSux() == 1 : "incorrect number of successors"; assert loopStart.isLinearScanLoopHeader() : "loop header flag must be set"; assert loopIdx >= 0 && loopIdx < numLoops : "loop index not set"; assert workList.isEmpty() : "work list must be empty before processing"; // add the end-block of the loop to the working list workList.add(loopEnd); setBlockInLoop(loopIdx, loopEnd); do { LIRBlock cur = workList.remove(workList.size() - 1); if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println(" processing B%d", cur.blockID()); } assert isBlockInLoop(loopIdx, cur) : "bit in loop map must be set when block is in work list"; // recursive processing of all predecessors ends when start block of loop is reached if (cur != loopStart) { for (int j = cur.numberOfPreds() - 1; j >= 0; j--) { LIRBlock pred = cur.predAt(j); if (!isBlockInLoop(loopIdx, pred)) { // this predecessor has not been processed yet, so add it to work list if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println(" pushing B%d", pred.blockID()); } workList.add(pred); setBlockInLoop(loopIdx, pred); } } } } while (!workList.isEmpty()); } } // check for non-natural loops (loops where the loop header does not dominate // all other loop blocks = loops with multiple entries). // such loops are ignored void clearNonNaturalLoops(LIRBlock startBlock) { for (int i = numLoops - 1; i >= 0; i--) { if (isBlockInLoop(i, startBlock)) { // loop i contains the entry block of the method. // this is not a natural loop, so ignore it if (C1XOptions.TraceLinearScanLevel >= 2) { TTY.println("Loop %d is non-natural, so it is ignored", i); } for (int blockId = maxBlockId - 1; blockId >= 0; blockId--) { clearBlockInLoop(i, blockId); } iterativeDominators = true; } } } void assignLoopDepth(LIRBlock startBlock) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("----- computing loop-depth and weight"); } initVisited(); assert workList.isEmpty() : "work list must be empty before processing"; workList.add(startBlock); do { LIRBlock cur = workList.remove(workList.size() - 1); if (!isVisited(cur)) { setVisited(cur); if (C1XOptions.TraceLinearScanLevel >= 4) { TTY.println("Computing loop depth for block B%d", cur.blockID()); } // compute loop-depth and loop-index for the block assert cur.loopDepth() == 0 : "cannot set loop-depth twice"; int i; int loopDepth = 0; int minLoopIdx = -1; for (i = numLoops - 1; i >= 0; i--) { if (isBlockInLoop(i, cur)) { loopDepth++; minLoopIdx = i; } } cur.setLoopDepth(loopDepth); cur.setLoopIndex(minLoopIdx); // append all unvisited successors to work list for (i = cur.numberOfSux() - 1; i >= 0; i--) { workList.add(cur.suxAt(i)); } for (LIRBlock ex : cur.getExceptionHandlerSuccessors()) { workList.add(ex); } } } while (!workList.isEmpty()); } int computeWeight(LIRBlock cur) { LIRBlock singleSux = null; if (cur.numberOfSux() == 1) { singleSux = cur.suxAt(0); } // limit loop-depth to 15 bit (only for security reason, it will never be so big) int weight = (cur.loopDepth() & 0x7FFF) << 16; int curBit = 15; // this is necessary for the (very rare) case that two successive blocks have // the same loop depth, but a different loop index (can happen for endless loops // with exception handlers) if (!cur.isLinearScanLoopHeader()) { weight |= 1 << curBit; } curBit--; // loop end blocks (blocks that end with a backward branch) are added // after all other blocks of the loop. if (!cur.isLinearScanLoopEnd()) { weight |= 1 << curBit; } curBit--; // critical edge split blocks are preferred because then they have a greater // probability to be completely empty //if (cur.isCriticalEdgeSplit()) { // weight |= 1 << curBit; //} //curBit--; // exceptions should not be thrown in normal control flow, so these blocks // are added as late as possible // if (!(cur.end() instanceof Throw) && (singleSux == null || !(singleSux.end() instanceof Throw))) { // weight |= 1 << curBit; // } // curBit--; // if (!(cur.end() instanceof Return) && (singleSux == null || !(singleSux.end() instanceof Return))) { // weight |= 1 << curBit; // } // curBit--; // exceptions handlers are added as late as possible if (!cur.isExceptionEntry()) { weight |= 1 << curBit; } curBit--; // guarantee that weight is > 0 weight |= 1; assert curBit >= 0 : "too many flags"; assert weight > 0 : "weight cannot become negative"; return weight; } boolean readyForProcessing(LIRBlock cur) { // Discount the edge just traveled. // When the number drops to zero, all forward branches were processed if (decForwardBranches(cur) != 0) { return false; } assert !linearScanOrder.contains(cur) : "block already processed (block can be ready only once)"; assert !workList.contains(cur) : "block already in work-list (block can be ready only once)"; return true; } void sortIntoWorkList(LIRBlock cur) { assert !workList.contains(cur) : "block already in work list"; int curWeight = computeWeight(cur); // the linearScanNumber is used to cache the weight of a block cur.setLinearScanNumber(curWeight); if (C1XOptions.StressLinearScan) { workList.add(0, cur); return; } workList.add(null); // provide space for new element int insertIdx = workList.size() - 1; while (insertIdx > 0 && workList.get(insertIdx - 1).linearScanNumber() > curWeight) { workList.set(insertIdx, workList.get(insertIdx - 1)); insertIdx--; } workList.set(insertIdx, cur); if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("Sorted B%d into worklist. new worklist:", cur.blockID()); for (int i = 0; i < workList.size(); i++) { TTY.println(String.format("%8d B%02d weight:%6x", i, workList.get(i).blockID(), workList.get(i).linearScanNumber())); } } for (int i = 0; i < workList.size(); i++) { assert workList.get(i).linearScanNumber() > 0 : "weight not set"; assert i == 0 || workList.get(i - 1).linearScanNumber() <= workList.get(i).linearScanNumber() : "incorrect order in worklist"; } } void appendBlock(LIRBlock cur) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("appending block B%d (weight 0x%06x) to linear-scan order", cur.blockID(), cur.linearScanNumber()); } assert !linearScanOrder.contains(cur) : "cannot add the same block twice"; // currently, the linear scan order and code emit order are equal. // therefore the linearScanNumber and the weight of a block must also // be equal. cur.setLinearScanNumber(linearScanOrder.size()); linearScanOrder.add(cur); } void computeOrder(LIRBlock startBlock) { if (C1XOptions.TraceLinearScanLevel >= 3) { TTY.println("----- computing final block order"); } // the start block is always the first block in the linear scan order linearScanOrder = new ArrayList<LIRBlock>(numBlocks); // appendBlock(startBlock); LIRBlock stdEntry = startBlock; //.suxAt(0); // start processing with standard entry block assert workList.isEmpty() : "list must be empty before processing"; if (readyForProcessing(stdEntry)) { sortIntoWorkList(stdEntry); } else { throw new CiBailout("the stdEntry must be ready for processing (otherwise, the method has no start block)"); } do { LIRBlock cur = workList.remove(workList.size() - 1); appendBlock(cur); int i; int numSux = cur.numberOfSux(); // changed loop order to get "intuitive" order of if- and else-blocks for (i = 0; i < numSux; i++) { LIRBlock sux = cur.suxAt(i); if (readyForProcessing(sux)) { sortIntoWorkList(sux); } } for (LIRBlock ex : cur.getExceptionHandlerSuccessors()) { if (readyForProcessing(ex)) { sortIntoWorkList(ex); } } } while (workList.size() > 0); } public void printBlocks() { if (C1XOptions.TraceLinearScanLevel >= 2) { TTY.println("----- loop information:"); for (LIRBlock cur : linearScanOrder) { TTY.print(String.format("%4d: B%02d: ", cur.linearScanNumber(), cur.blockID())); for (int loopIdx = 0; loopIdx < numLoops; loopIdx++) { TTY.print(String.format("%d = %b ", loopIdx, isBlockInLoop(loopIdx, cur))); } TTY.println(String.format(" . loopIndex: %2d, loopDepth: %2d", cur.loopIndex(), cur.loopDepth())); } } if (C1XOptions.TraceLinearScanLevel >= 1) { TTY.println("----- linear-scan block order:"); for (LIRBlock cur : linearScanOrder) { TTY.print(String.format("%4d: B%02d loop: %2d depth: %2d", cur.linearScanNumber(), cur.blockID(), cur.loopIndex(), cur.loopDepth())); TTY.print(cur.isExceptionEntry() ? " ex" : " "); TTY.print(cur.isLinearScanLoopHeader() ? " lh" : " "); TTY.print(cur.isLinearScanLoopEnd() ? " le" : " "); TTY.print(" dom: null "); if (cur.numberOfPreds() > 0) { TTY.print(" preds: "); for (int j = 0; j < cur.numberOfPreds(); j++) { LIRBlock pred = cur.predAt(j); TTY.print("B%d ", pred.blockID()); } } if (cur.numberOfSux() > 0) { TTY.print(" sux: "); for (int j = 0; j < cur.numberOfSux(); j++) { LIRBlock sux = cur.suxAt(j); TTY.print("B%d ", sux.blockID()); } } TTY.println(); } } } boolean verify() { /* assert linearScanOrder.size() == numBlocks : "wrong number of blocks in list"; if (C1XOptions.StressLinearScan) { // blocks are scrambled when StressLinearScan is used return true; } // check that all successors of a block have a higher linear-scan-number // and that all predecessors of a block have a lower linear-scan-number // (only backward branches of loops are ignored) int i; for (i = 0; i < linearScanOrder.size(); i++) { BlockBegin cur = linearScanOrder.get(i); assert cur.linearScanNumber() == i : "incorrect linearScanNumber"; assert cur.linearScanNumber() >= 0 && cur.linearScanNumber() == linearScanOrder.indexOf(cur) : "incorrect linearScanNumber"; for (BlockBegin sux : cur.end().successors()) { assert sux.linearScanNumber() >= 0 && sux.linearScanNumber() == linearScanOrder.indexOf(sux) : "incorrect linearScanNumber"; if (!cur.checkBlockFlag(BlockBegin.BlockFlag.LinearScanLoopEnd)) { assert cur.linearScanNumber() < sux.linearScanNumber() : "invalid order"; } if (cur.loopDepth() == sux.loopDepth()) { assert cur.loopIndex() == sux.loopIndex() || sux.checkBlockFlag(BlockBegin.BlockFlag.LinearScanLoopHeader) : "successing blocks with same loop depth must have same loop index"; } } for (BlockBegin pred : cur.predecessors()) { assert pred.linearScanNumber() >= 0 && pred.linearScanNumber() == linearScanOrder.indexOf(pred) : "incorrect linearScanNumber"; if (!cur.checkBlockFlag(BlockBegin.BlockFlag.LinearScanLoopHeader)) { assert cur.linearScanNumber() > pred.linearScanNumber() : "invalid order"; } if (cur.loopDepth() == pred.loopDepth()) { assert cur.loopIndex() == pred.loopIndex() || cur.checkBlockFlag(BlockBegin.BlockFlag.LinearScanLoopHeader) : "successing blocks with same loop depth must have same loop index"; } assert cur.dominator().linearScanNumber() <= pred.linearScanNumber() : "dominator must be before predecessors"; } // check dominator if (i == 0) { assert cur.dominator() == null : "first block has no dominator"; } else { assert cur.dominator() != null : "all but first block must have dominator"; } assert cur.numberOfPreds() != 1 || cur.dominator() == cur.predAt(0) || cur.isExceptionEntry() : "Single predecessor must also be dominator"; } // check that all loops are continuous for (int loopIdx = 0; loopIdx < numLoops; loopIdx++) { int blockIdx = 0; assert !isBlockInLoop(loopIdx, linearScanOrder.get(blockIdx)) : "the first block must not be present in any loop"; // skip blocks before the loop while (blockIdx < numBlocks && !isBlockInLoop(loopIdx, linearScanOrder.get(blockIdx))) { blockIdx++; } // skip blocks of loop while (blockIdx < numBlocks && isBlockInLoop(loopIdx, linearScanOrder.get(blockIdx))) { blockIdx++; } // after the first non-loop block : there must not be another loop-block while (blockIdx < numBlocks) { assert !isBlockInLoop(loopIdx, linearScanOrder.get(blockIdx)) : "loop not continuous in linear-scan order"; blockIdx++; } } */ return true; } }