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/*
* 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 "BytecodeBasicBlock.h"
#include "CodeBlock.h"
#include "JSCInlines.h"
#include "PreciseJumpTargets.h"
namespace JSC {
void BytecodeBasicBlock::shrinkToFit()
{
m_bytecodeOffsets.shrinkToFit();
m_successors.shrinkToFit();
}
static bool isBranch(OpcodeID opcodeID)
{
switch (opcodeID) {
case op_jmp:
case op_jtrue:
case op_jfalse:
case op_jeq_null:
case op_jneq_null:
case op_jneq_ptr:
case op_jless:
case op_jlesseq:
case op_jgreater:
case op_jgreatereq:
case op_jnless:
case op_jnlesseq:
case op_jngreater:
case op_jngreatereq:
case op_switch_imm:
case op_switch_char:
case op_switch_string:
case op_save:
return true;
default:
return false;
}
}
static bool isUnconditionalBranch(OpcodeID opcodeID)
{
switch (opcodeID) {
case op_jmp:
return true;
default:
return false;
}
}
static bool isTerminal(OpcodeID opcodeID)
{
switch (opcodeID) {
case op_ret:
case op_end:
return true;
default:
return false;
}
}
static bool isThrow(OpcodeID opcodeID)
{
switch (opcodeID) {
case op_throw:
case op_throw_static_error:
return true;
default:
return false;
}
}
static bool isJumpTarget(OpcodeID opcodeID, const Vector<unsigned, 32>& jumpTargets, unsigned bytecodeOffset)
{
if (opcodeID == op_catch)
return true;
return std::binary_search(jumpTargets.begin(), jumpTargets.end(), bytecodeOffset);
}
static void linkBlocks(BytecodeBasicBlock* predecessor, BytecodeBasicBlock* successor)
{
predecessor->addSuccessor(successor);
}
void computeBytecodeBasicBlocks(CodeBlock* codeBlock, Vector<std::unique_ptr<BytecodeBasicBlock>>& basicBlocks)
{
Vector<unsigned, 32> jumpTargets;
computePreciseJumpTargets(codeBlock, jumpTargets);
// Create the entry and exit basic blocks.
basicBlocks.reserveCapacity(jumpTargets.size() + 2);
auto entry = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::EntryBlock);
auto firstBlock = std::make_unique<BytecodeBasicBlock>(0, 0);
linkBlocks(entry.get(), firstBlock.get());
basicBlocks.append(WTFMove(entry));
BytecodeBasicBlock* current = firstBlock.get();
basicBlocks.append(WTFMove(firstBlock));
auto exit = std::make_unique<BytecodeBasicBlock>(BytecodeBasicBlock::ExitBlock);
bool nextInstructionIsLeader = false;
Interpreter* interpreter = codeBlock->vm()->interpreter;
Instruction* instructionsBegin = codeBlock->instructions().begin();
unsigned instructionCount = codeBlock->instructions().size();
for (unsigned bytecodeOffset = 0; bytecodeOffset < instructionCount;) {
OpcodeID opcodeID = interpreter->getOpcodeID(instructionsBegin[bytecodeOffset].u.opcode);
unsigned opcodeLength = opcodeLengths[opcodeID];
bool createdBlock = false;
// If the current bytecode is a jump target, then it's the leader of its own basic block.
if (isJumpTarget(opcodeID, jumpTargets, bytecodeOffset) || nextInstructionIsLeader) {
auto newBlock = std::make_unique<BytecodeBasicBlock>(bytecodeOffset, opcodeLength);
current = newBlock.get();
basicBlocks.append(WTFMove(newBlock));
createdBlock = true;
nextInstructionIsLeader = false;
bytecodeOffset += opcodeLength;
}
// If the current bytecode is a branch or a return, then the next instruction is the leader of its own basic block.
if (isBranch(opcodeID) || isTerminal(opcodeID) || isThrow(opcodeID))
nextInstructionIsLeader = true;
if (createdBlock)
continue;
// Otherwise, just add to the length of the current block.
current->addBytecodeLength(opcodeLength);
bytecodeOffset += opcodeLength;
}
// Link basic blocks together.
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* block = basicBlocks[i].get();
if (block->isEntryBlock() || block->isExitBlock())
continue;
bool fallsThrough = true;
for (unsigned bytecodeOffset = block->leaderBytecodeOffset(); bytecodeOffset < block->leaderBytecodeOffset() + block->totalBytecodeLength();) {
const Instruction& currentInstruction = instructionsBegin[bytecodeOffset];
OpcodeID opcodeID = interpreter->getOpcodeID(currentInstruction.u.opcode);
unsigned opcodeLength = opcodeLengths[opcodeID];
// If we found a terminal bytecode, link to the exit block.
if (isTerminal(opcodeID)) {
ASSERT(bytecodeOffset + opcodeLength == block->leaderBytecodeOffset() + block->totalBytecodeLength());
linkBlocks(block, exit.get());
fallsThrough = false;
break;
}
// If we found a throw, get the HandlerInfo for this instruction to see where we will jump.
// If there isn't one, treat this throw as a terminal. This is true even if we have a finally
// block because the finally block will create its own catch, which will generate a HandlerInfo.
if (isThrow(opcodeID)) {
ASSERT(bytecodeOffset + opcodeLength == block->leaderBytecodeOffset() + block->totalBytecodeLength());
HandlerInfo* handler = codeBlock->handlerForBytecodeOffset(bytecodeOffset);
fallsThrough = false;
if (!handler) {
linkBlocks(block, exit.get());
break;
}
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
if (handler->target == otherBlock->leaderBytecodeOffset()) {
linkBlocks(block, otherBlock);
break;
}
}
break;
}
// If we found a branch, link to the block(s) that we jump to.
if (isBranch(opcodeID)) {
ASSERT(bytecodeOffset + opcodeLength == block->leaderBytecodeOffset() + block->totalBytecodeLength());
Vector<unsigned, 1> bytecodeOffsetsJumpedTo;
findJumpTargetsForBytecodeOffset(codeBlock, bytecodeOffset, bytecodeOffsetsJumpedTo);
for (unsigned i = 0; i < basicBlocks.size(); i++) {
BytecodeBasicBlock* otherBlock = basicBlocks[i].get();
if (bytecodeOffsetsJumpedTo.contains(otherBlock->leaderBytecodeOffset()))
linkBlocks(block, otherBlock);
}
if (isUnconditionalBranch(opcodeID))
fallsThrough = false;
break;
}
bytecodeOffset += opcodeLength;
}
// If we fall through then link to the next block in program order.
if (fallsThrough) {
ASSERT(i + 1 < basicBlocks.size());
BytecodeBasicBlock* nextBlock = basicBlocks[i + 1].get();
linkBlocks(block, nextBlock);
}
}
basicBlocks.append(WTFMove(exit));
for (auto& basicBlock : basicBlocks)
basicBlock->shrinkToFit();
}
} // namespace JSC
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