--- /dev/null 2017-01-22 10:16:57.869617664 -0800
+++ new/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.lir/src/org/graalvm/compiler/lir/EdgeMoveOptimizer.java 2017-02-15 17:05:17.673150717 -0800
@@ -0,0 +1,294 @@
+/*
+ * Copyright (c) 2009, 2015, 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 org.graalvm.compiler.lir;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.graalvm.compiler.core.common.cfg.AbstractBlockBase;
+import org.graalvm.compiler.lir.StandardOp.LoadConstantOp;
+import org.graalvm.compiler.lir.StandardOp.MoveOp;
+import org.graalvm.compiler.lir.StandardOp.ValueMoveOp;
+import org.graalvm.compiler.lir.gen.LIRGenerationResult;
+import org.graalvm.compiler.lir.phases.PostAllocationOptimizationPhase;
+
+import jdk.vm.ci.code.TargetDescription;
+
+/**
+ * This class optimizes moves, particularly those that result from eliminating SSA form.
+ *
+ * When a block has more than one predecessor, and all predecessors end with the
+ * {@linkplain Optimizer#same(LIRInstruction, LIRInstruction) same} sequence of {@linkplain MoveOp
+ * move} instructions, then these sequences can be replaced with a single copy of the sequence at
+ * the beginning of the block.
+ *
+ * Similarly, when a block has more than one successor, then same sequences of moves at the
+ * beginning of the successors can be placed once at the end of the block. But because the moves
+ * must be inserted before all branch instructions, this works only when there is exactly one
+ * conditional branch at the end of the block (because the moves must be inserted before all
+ * branches, but after all compares).
+ *
+ * This optimization affects all kind of moves (reg->reg, reg->stack and stack->reg).
+ * Because this optimization works best when a block contains only a few moves, it has a huge impact
+ * on the number of blocks that are totally empty.
+ */
+public final class EdgeMoveOptimizer extends PostAllocationOptimizationPhase {
+
+ @Override
+ protected void run(TargetDescription target, LIRGenerationResult lirGenRes, PostAllocationOptimizationContext context) {
+ LIR ir = lirGenRes.getLIR();
+ Optimizer optimizer = new Optimizer(ir);
+
+ AbstractBlockBase[] blockList = ir.linearScanOrder();
+ // ignore the first block in the list (index 0 is not processed)
+ for (int i = blockList.length - 1; i >= 1; i--) {
+ AbstractBlockBase block = blockList[i];
+
+ if (block.getPredecessorCount() > 1) {
+ optimizer.optimizeMovesAtBlockEnd(block);
+ }
+ if (block.getSuccessorCount() == 2) {
+ optimizer.optimizeMovesAtBlockBegin(block);
+ }
+ }
+ }
+
+ private static final class Optimizer {
+ private final List> edgeInstructionSeqences;
+ private LIR ir;
+
+ Optimizer(LIR ir) {
+ this.ir = ir;
+ edgeInstructionSeqences = new ArrayList<>(4);
+ }
+
+ /**
+ * Determines if two operations are both {@linkplain MoveOp moves} that have the same source
+ * and {@linkplain MoveOp#getResult() destination} operands.
+ *
+ * @param op1 the first instruction to compare
+ * @param op2 the second instruction to compare
+ * @return {@code true} if {@code op1} and {@code op2} are the same by the above algorithm
+ */
+ private static boolean same(LIRInstruction op1, LIRInstruction op2) {
+ assert op1 != null;
+ assert op2 != null;
+
+ if (op1 instanceof ValueMoveOp && op2 instanceof ValueMoveOp) {
+ ValueMoveOp move1 = (ValueMoveOp) op1;
+ ValueMoveOp move2 = (ValueMoveOp) op2;
+ if (move1.getInput().equals(move2.getInput()) && move1.getResult().equals(move2.getResult())) {
+ // these moves are exactly equal and can be optimized
+ return true;
+ }
+ } else if (op1 instanceof LoadConstantOp && op2 instanceof LoadConstantOp) {
+ LoadConstantOp move1 = (LoadConstantOp) op1;
+ LoadConstantOp move2 = (LoadConstantOp) op2;
+ if (move1.getConstant().equals(move2.getConstant()) && move1.getResult().equals(move2.getResult())) {
+ // these moves are exactly equal and can be optimized
+ return true;
+ }
+ }
+ return false;
+ }
+
+ /**
+ * Moves the longest {@linkplain #same common} subsequence at the end all predecessors of
+ * {@code block} to the start of {@code block}.
+ */
+ private void optimizeMovesAtBlockEnd(AbstractBlockBase block) {
+ for (AbstractBlockBase pred : block.getPredecessors()) {
+ if (pred == block) {
+ // currently we can't handle this correctly.
+ return;
+ }
+ }
+
+ // clear all internal data structures
+ edgeInstructionSeqences.clear();
+
+ int numPreds = block.getPredecessorCount();
+ assert numPreds > 1 : "do not call otherwise";
+
+ // setup a list with the LIR instructions of all predecessors
+ for (AbstractBlockBase pred : block.getPredecessors()) {
+ assert pred != null;
+ assert ir.getLIRforBlock(pred) != null;
+ List predInstructions = ir.getLIRforBlock(pred);
+
+ if (pred.getSuccessorCount() != 1) {
+ // this can happen with switch-statements where multiple edges are between
+ // the same blocks.
+ return;
+ }
+
+ assert pred.getSuccessors()[0] == block : "invalid control flow";
+ assert predInstructions.get(predInstructions.size() - 1) instanceof StandardOp.JumpOp : "block must end with unconditional jump";
+
+ if (predInstructions.get(predInstructions.size() - 1).hasState()) {
+ // can not optimize instructions that have debug info
+ return;
+ }
+
+ // ignore the unconditional branch at the end of the block
+ List seq = predInstructions.subList(0, predInstructions.size() - 1);
+ edgeInstructionSeqences.add(seq);
+ }
+
+ // process lir-instructions while all predecessors end with the same instruction
+ while (true) {
+ List seq = edgeInstructionSeqences.get(0);
+ if (seq.isEmpty()) {
+ return;
+ }
+
+ LIRInstruction op = last(seq);
+ for (int i = 1; i < numPreds; ++i) {
+ List otherSeq = edgeInstructionSeqences.get(i);
+ if (otherSeq.isEmpty() || !same(op, last(otherSeq))) {
+ return;
+ }
+ }
+
+ // insert the instruction at the beginning of the current block
+ ir.getLIRforBlock(block).add(1, op);
+
+ // delete the instruction at the end of all predecessors
+ for (int i = 0; i < numPreds; i++) {
+ seq = edgeInstructionSeqences.get(i);
+ removeLast(seq);
+ }
+ }
+ }
+
+ /**
+ * Moves the longest {@linkplain #same common} subsequence at the start of all successors of
+ * {@code block} to the end of {@code block} just prior to the branch instruction ending
+ * {@code block}.
+ */
+ private void optimizeMovesAtBlockBegin(AbstractBlockBase block) {
+
+ edgeInstructionSeqences.clear();
+ int numSux = block.getSuccessorCount();
+
+ List instructions = ir.getLIRforBlock(block);
+
+ assert numSux == 2 : "method should not be called otherwise";
+
+ LIRInstruction lastInstruction = instructions.get(instructions.size() - 1);
+ if (lastInstruction.hasState()) {
+ // cannot optimize instructions when debug info is needed
+ return;
+ }
+
+ LIRInstruction branch = lastInstruction;
+ if (!(branch instanceof StandardOp.BranchOp) || branch.hasOperands()) {
+ // Only blocks that end with a conditional branch are optimized.
+ // In addition, a conditional branch with operands (including state) cannot
+ // be optimized. Moving a successor instruction before such a branch may
+ // interfere with the operands of the branch. For example, a successive move
+ // instruction may redefine an input operand of the branch.
+ return;
+ }
+
+ // Now it is guaranteed that the block ends with a conditional branch.
+ // The instructions are inserted at the end of the block before the branch.
+ int insertIdx = instructions.size() - 1;
+
+ // setup a list with the lir-instructions of all successors
+ for (AbstractBlockBase sux : block.getSuccessors()) {
+ List suxInstructions = ir.getLIRforBlock(sux);
+
+ assert suxInstructions.get(0) instanceof StandardOp.LabelOp : "block must start with label";
+
+ if (sux.getPredecessorCount() != 1) {
+ // this can happen with switch-statements where multiple edges are between
+ // the same blocks.
+ return;
+ }
+ assert sux.getPredecessors()[0] == block : "invalid control flow";
+
+ // ignore the label at the beginning of the block
+ List seq = suxInstructions.subList(1, suxInstructions.size());
+ edgeInstructionSeqences.add(seq);
+ }
+
+ // process LIR instructions while all successors begin with the same instruction
+ while (true) {
+ List seq = edgeInstructionSeqences.get(0);
+ if (seq.isEmpty()) {
+ return;
+ }
+
+ LIRInstruction op = first(seq);
+ for (int i = 1; i < numSux; i++) {
+ List otherSeq = edgeInstructionSeqences.get(i);
+ if (otherSeq.isEmpty() || !same(op, first(otherSeq))) {
+ // these instructions are different and cannot be optimized .
+ // no further optimization possible
+ return;
+ }
+ }
+
+ // insert instruction at end of current block
+ ir.getLIRforBlock(block).add(insertIdx, op);
+ insertIdx++;
+
+ // delete the instructions at the beginning of all successors
+ for (int i = 0; i < numSux; i++) {
+ seq = edgeInstructionSeqences.get(i);
+ removeFirst(seq);
+ }
+ }
+ }
+
+ /**
+ * Gets the first element from a LIR instruction sequence.
+ */
+ private static LIRInstruction first(List seq) {
+ return seq.get(0);
+ }
+
+ /**
+ * Gets the last element from a LIR instruction sequence.
+ */
+ private static LIRInstruction last(List seq) {
+ return seq.get(seq.size() - 1);
+ }
+
+ /**
+ * Removes the first element from a LIR instruction sequence.
+ */
+ private static void removeFirst(List seq) {
+ seq.remove(0);
+ }
+
+ /**
+ * Removes the last element from a LIR instruction sequence.
+ */
+ private static void removeLast(List seq) {
+ seq.remove(seq.size() - 1);
+ }
+
+ }
+}