Imported QtWebKit TP3 (git b57bc6801f1876c3220d5a4bfea33d620d477443)

Change-Id: I3b1d8a2808782c9f34d50240000e20cb38d3680f
Reviewed-by: Konstantin Tokarev <annulen@yandex.ru>

1 files changed, 348 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/bytecode/BytecodeLivenessAnalysis.cpp b/Source/JavaScriptCore/bytecode/BytecodeLivenessAnalysis.cpp
new file mode 100644
index 000000000..7228b0333
--- /dev/null
+++ b/Source/JavaScriptCore/bytecode/BytecodeLivenessAnalysis.cpp
@@ -0,0 +1,348 @@
+/*
+ * Copyright (C) 2013, 2015 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "BytecodeLivenessAnalysis.h"
+
+#include "BytecodeKills.h"
+#include "BytecodeLivenessAnalysisInlines.h"
+#include "BytecodeUseDef.h"
+#include "CodeBlock.h"
+#include "FullBytecodeLiveness.h"
+#include "PreciseJumpTargets.h"
+
+namespace JSC {
+
+BytecodeLivenessAnalysis::BytecodeLivenessAnalysis(CodeBlock* codeBlock)
+    : m_codeBlock(codeBlock)
+{
+    ASSERT(m_codeBlock);
+    compute();
+}
+
+static bool isValidRegisterForLiveness(CodeBlock* codeBlock, int operand)
+{
+    if (codeBlock->isConstantRegisterIndex(operand))
+        return false;
+    
+    VirtualRegister virtualReg(operand);
+    return virtualReg.isLocal();
+}
+
+static unsigned getLeaderOffsetForBasicBlock(std::unique_ptr<BytecodeBasicBlock>* basicBlock)
+{
+    return (*basicBlock)->leaderBytecodeOffset();
+}
+
+static BytecodeBasicBlock* findBasicBlockWithLeaderOffset(Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks, unsigned leaderOffset)
+{
+    return (*tryBinarySearch<std::unique_ptr<BytecodeBasicBlock>, unsigned>(basicBlocks, basicBlocks.size(), leaderOffset, getLeaderOffsetForBasicBlock)).get();
+}
+
+static bool blockContainsBytecodeOffset(BytecodeBasicBlock* block, unsigned bytecodeOffset)
+{
+    unsigned leaderOffset = block->leaderBytecodeOffset();
+    return bytecodeOffset >= leaderOffset && bytecodeOffset < leaderOffset + block->totalBytecodeLength();
+}
+
+static BytecodeBasicBlock* findBasicBlockForBytecodeOffset(Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks, unsigned bytecodeOffset)
+{
+/*
+    for (unsigned i = 0; i < basicBlocks.size(); i++) {
+        if (blockContainsBytecodeOffset(basicBlocks[i].get(), bytecodeOffset))
+            return basicBlocks[i].get();
+    }
+    return 0;
+*/
+    std::unique_ptr<BytecodeBasicBlock>* basicBlock = approximateBinarySearch<std::unique_ptr<BytecodeBasicBlock>, unsigned>(
+        basicBlocks, basicBlocks.size(), bytecodeOffset, getLeaderOffsetForBasicBlock);
+    // We found the block we were looking for.
+    if (blockContainsBytecodeOffset((*basicBlock).get(), bytecodeOffset))
+        return (*basicBlock).get();
+
+    // Basic block is to the left of the returned block.
+    if (bytecodeOffset < (*basicBlock)->leaderBytecodeOffset()) {
+        ASSERT(basicBlock - 1 >= basicBlocks.data());
+        ASSERT(blockContainsBytecodeOffset(basicBlock[-1].get(), bytecodeOffset));
+        return basicBlock[-1].get();
+    }
+
+    // Basic block is to the right of the returned block.
+    ASSERT(&basicBlock[1] <= &basicBlocks.last());
+    ASSERT(blockContainsBytecodeOffset(basicBlock[1].get(), bytecodeOffset));
+    return basicBlock[1].get();
+}
+
+// Simplified interface to bytecode use/def, which determines defs first and then uses, and includes
+// exception handlers in the uses.
+template<typename UseFunctor, typename DefFunctor>
+static void stepOverInstruction(CodeBlock* codeBlock, BytecodeBasicBlock* block, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks, unsigned bytecodeOffset, const UseFunctor& use, const DefFunctor& def)
+{
+    // This abstractly execute the instruction in reverse. Instructions logically first use operands and
+    // then define operands. This logical ordering is necessary for operations that use and def the same
+    // operand, like:
+    //
+    //     op_add loc1, loc1, loc2
+    //
+    // The use of loc1 happens before the def of loc1. That's a semantic requirement since the add
+    // operation cannot travel forward in time to read the value that it will produce after reading that
+    // value. Since we are executing in reverse, this means that we must do defs before uses (reverse of
+    // uses before defs).
+    //
+    // Since this is a liveness analysis, this ordering ends up being particularly important: if we did
+    // uses before defs, then the add operation above would appear to not have loc1 live, since we'd
+    // first add it to the out set (the use), and then we'd remove it (the def).
+    
+    computeDefsForBytecodeOffset(
+        codeBlock, block, bytecodeOffset,
+        [&] (CodeBlock* codeBlock, Instruction*, OpcodeID, int operand) {
+            if (isValidRegisterForLiveness(codeBlock, operand))
+                def(VirtualRegister(operand).toLocal());
+        });
+
+    computeUsesForBytecodeOffset(
+        codeBlock, block, bytecodeOffset,
+        [&] (CodeBlock* codeBlock, Instruction*, OpcodeID, int operand) {
+            if (isValidRegisterForLiveness(codeBlock, operand))
+                use(VirtualRegister(operand).toLocal());
+        });
+
+    // If we have an exception handler, we want the live-in variables of the 
+    // exception handler block to be included in the live-in of this particular bytecode.
+    if (HandlerInfo* handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset)) {
+        BytecodeBasicBlock* handlerBlock = findBasicBlockWithLeaderOffset(basicBlocks, handler->target);
+        ASSERT(handlerBlock);
+        handlerBlock->in().forEachSetBit(use);
+    }
+}
+
+static void stepOverInstruction(CodeBlock* codeBlock, BytecodeBasicBlock* block, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks, unsigned bytecodeOffset, FastBitVector& out)
+{
+    stepOverInstruction(
+        codeBlock, block, basicBlocks, bytecodeOffset,
+        [&] (unsigned bitIndex) {
+            // This is the use functor, so we set the bit.
+            out.set(bitIndex);
+        },
+        [&] (unsigned bitIndex) {
+            // This is the def functor, so we clear the bit.
+            out.clear(bitIndex);
+        });
+}
+
+static void computeLocalLivenessForBytecodeOffset(CodeBlock* codeBlock, BytecodeBasicBlock* block, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks, unsigned targetOffset, FastBitVector& result)
+{
+    ASSERT(!block->isExitBlock());
+    ASSERT(!block->isEntryBlock());
+
+    FastBitVector out = block->out();
+
+    for (int i = block->bytecodeOffsets().size() - 1; i >= 0; i--) {
+        unsigned bytecodeOffset = block->bytecodeOffsets()[i];
+        if (targetOffset > bytecodeOffset)
+            break;
+        
+        stepOverInstruction(codeBlock, block, basicBlocks, bytecodeOffset, out);
+    }
+
+    result.set(out);
+}
+
+static void computeLocalLivenessForBlock(CodeBlock* codeBlock, BytecodeBasicBlock* block, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
+{
+    if (block->isExitBlock() || block->isEntryBlock())
+        return;
+    computeLocalLivenessForBytecodeOffset(codeBlock, block, basicBlocks, block->leaderBytecodeOffset(), block->in());
+}
+
+void BytecodeLivenessAnalysis::runLivenessFixpoint()
+{
+    UnlinkedCodeBlock* unlinkedCodeBlock = m_codeBlock->unlinkedCodeBlock();
+    unsigned numberOfVariables = unlinkedCodeBlock->m_numCalleeLocals;
+
+    for (unsigned i = 0; i < m_basicBlocks.size(); i++) {
+        BytecodeBasicBlock* block = m_basicBlocks[i].get();
+        block->in().resize(numberOfVariables);
+        block->out().resize(numberOfVariables);
+    }
+
+    bool changed;
+    m_basicBlocks.last()->in().clearAll();
+    m_basicBlocks.last()->out().clearAll();
+    FastBitVector newOut;
+    newOut.resize(m_basicBlocks.last()->out().numBits());
+    do {
+        changed = false;
+        for (unsigned i = m_basicBlocks.size() - 1; i--;) {
+            BytecodeBasicBlock* block = m_basicBlocks[i].get();
+            newOut.clearAll();
+            for (unsigned j = 0; j < block->successors().size(); j++)
+                newOut.merge(block->successors()[j]->in());
+            bool outDidChange = block->out().setAndCheck(newOut);
+            computeLocalLivenessForBlock(m_codeBlock, block, m_basicBlocks);
+            changed |= outDidChange;
+        }
+    } while (changed);
+}
+
+void BytecodeLivenessAnalysis::getLivenessInfoAtBytecodeOffset(unsigned bytecodeOffset, FastBitVector& result)
+{
+    BytecodeBasicBlock* block = findBasicBlockForBytecodeOffset(m_basicBlocks, bytecodeOffset);
+    ASSERT(block);
+    ASSERT(!block->isEntryBlock());
+    ASSERT(!block->isExitBlock());
+    result.resize(block->out().numBits());
+    computeLocalLivenessForBytecodeOffset(m_codeBlock, block, m_basicBlocks, bytecodeOffset, result);
+}
+
+bool BytecodeLivenessAnalysis::operandIsLiveAtBytecodeOffset(int operand, unsigned bytecodeOffset)
+{
+    if (operandIsAlwaysLive(operand))
+        return true;
+    FastBitVector result;
+    getLivenessInfoAtBytecodeOffset(bytecodeOffset, result);
+    return operandThatIsNotAlwaysLiveIsLive(result, operand);
+}
+
+FastBitVector BytecodeLivenessAnalysis::getLivenessInfoAtBytecodeOffset(unsigned bytecodeOffset)
+{
+    FastBitVector out;
+    getLivenessInfoAtBytecodeOffset(bytecodeOffset, out);
+    return out;
+}
+
+void BytecodeLivenessAnalysis::computeFullLiveness(FullBytecodeLiveness& result)
+{
+    FastBitVector out;
+    
+    result.m_map.resize(m_codeBlock->instructions().size());
+    
+    for (unsigned i = m_basicBlocks.size(); i--;) {
+        BytecodeBasicBlock* block = m_basicBlocks[i].get();
+        if (block->isEntryBlock() || block->isExitBlock())
+            continue;
+        
+        out = block->out();
+        
+        for (unsigned i = block->bytecodeOffsets().size(); i--;) {
+            unsigned bytecodeOffset = block->bytecodeOffsets()[i];
+            stepOverInstruction(m_codeBlock, block, m_basicBlocks, bytecodeOffset, out);
+            result.m_map[bytecodeOffset] = out;
+        }
+    }
+}
+
+void BytecodeLivenessAnalysis::computeKills(BytecodeKills& result)
+{
+    FastBitVector out;
+    
+    result.m_codeBlock = m_codeBlock;
+    result.m_killSets = std::make_unique<BytecodeKills::KillSet[]>(m_codeBlock->instructions().size());
+    
+    for (unsigned i = m_basicBlocks.size(); i--;) {
+        BytecodeBasicBlock* block = m_basicBlocks[i].get();
+        if (block->isEntryBlock() || block->isExitBlock())
+            continue;
+        
+        out = block->out();
+        
+        for (unsigned i = block->bytecodeOffsets().size(); i--;) {
+            unsigned bytecodeOffset = block->bytecodeOffsets()[i];
+            stepOverInstruction(
+                m_codeBlock, block, m_basicBlocks, bytecodeOffset,
+                [&] (unsigned index) {
+                    // This is for uses.
+                    if (out.get(index))
+                        return;
+                    result.m_killSets[bytecodeOffset].add(index);
+                    out.set(index);
+                },
+                [&] (unsigned index) {
+                    // This is for defs.
+                    out.clear(index);
+                });
+        }
+    }
+}
+
+void BytecodeLivenessAnalysis::dumpResults()
+{
+    Interpreter* interpreter = m_codeBlock->vm()->interpreter;
+    Instruction* instructionsBegin = m_codeBlock->instructions().begin();
+    for (unsigned i = 0; i < m_basicBlocks.size(); i++) {
+        BytecodeBasicBlock* block = m_basicBlocks[i].get();
+        dataLogF("\nBytecode basic block %u: %p (offset: %u, length: %u)\n", i, block, block->leaderBytecodeOffset(), block->totalBytecodeLength());
+        dataLogF("Successors: ");
+        for (unsigned j = 0; j < block->successors().size(); j++) {
+            BytecodeBasicBlock* successor = block->successors()[j];
+            dataLogF("%p ", successor);
+        }
+        dataLogF("\n");
+        if (block->isEntryBlock()) {
+            dataLogF("Entry block %p\n", block);
+            continue;
+        }
+        if (block->isExitBlock()) {
+            dataLogF("Exit block: %p\n", block);
+            continue;
+        }
+        for (unsigned bytecodeOffset = block->leaderBytecodeOffset(); bytecodeOffset < block->leaderBytecodeOffset() + block->totalBytecodeLength();) {
+            const Instruction* currentInstruction = &instructionsBegin[bytecodeOffset];
+
+            dataLogF("Live variables: ");
+            FastBitVector liveBefore = getLivenessInfoAtBytecodeOffset(bytecodeOffset);
+            for (unsigned j = 0; j < liveBefore.numBits(); j++) {
+                if (liveBefore.get(j))
+                    dataLogF("%u ", j);
+            }
+            dataLogF("\n");
+            m_codeBlock->dumpBytecode(WTF::dataFile(), m_codeBlock->globalObject()->globalExec(), instructionsBegin, currentInstruction);
+
+            OpcodeID opcodeID = interpreter->getOpcodeID(instructionsBegin[bytecodeOffset].u.opcode);
+            unsigned opcodeLength = opcodeLengths[opcodeID];
+            bytecodeOffset += opcodeLength;
+        }
+
+        dataLogF("Live variables: ");
+        FastBitVector liveAfter = block->out();
+        for (unsigned j = 0; j < liveAfter.numBits(); j++) {
+            if (liveAfter.get(j))
+                dataLogF("%u ", j);
+        }
+        dataLogF("\n");
+    }
+}
+
+void BytecodeLivenessAnalysis::compute()
+{
+    computeBytecodeBasicBlocks(m_codeBlock, m_basicBlocks);
+    ASSERT(m_basicBlocks.size());
+    runLivenessFixpoint();
+
+    if (Options::dumpBytecodeLivenessResults())
+        dumpResults();
+}
+
+} // namespace JSC