Source/JavaScriptCore/bytecode/PreciseJumpTargets.cpp

/*
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#include "config.h"
#include "PreciseJumpTargets.h"

#include "InterpreterInlines.h"
#include "JSCInlines.h"
#include "PreciseJumpTargetsInlines.h"

namespace JSC {

template <size_t vectorSize, typename Block, typename Instruction>
static void getJumpTargetsForBytecodeOffset(Block* codeBlock, Instruction* instructionsBegin, unsigned bytecodeOffset, Vector<unsigned, vectorSize>& out)
{
    OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
    extractStoredJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, [&](int32_t& relativeOffset) {
        out.append(bytecodeOffset + relativeOffset);
    });
    // op_loop_hint does not have jump target stored in bytecode instructions.
    if (opcodeID == op_loop_hint)
        out.append(bytecodeOffset);
    else if (opcodeID == op_enter && codeBlock->hasTailCalls() && Options::optimizeRecursiveTailCalls()) {
        // We need to insert a jump after op_enter, so recursive tail calls have somewhere to jump to.
        // But we only want to pay that price for functions that have at least one tail call.
        out.append(bytecodeOffset + opcodeLengths[op_enter]);
    }
}

enum class ComputePreciseJumpTargetsMode {
    FollowCodeBlockClaim,
    ForceCompute,
};

template<ComputePreciseJumpTargetsMode Mode, typename Block, typename Instruction, size_t vectorSize>
void computePreciseJumpTargetsInternal(Block* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<unsigned, vectorSize>& out)
{
    ASSERT(out.isEmpty());

    // The code block has a superset of the jump targets. So if it claims to have none, we are done.
    if (Mode == ComputePreciseJumpTargetsMode::FollowCodeBlockClaim && !codeBlock->numberOfJumpTargets())
        return;
    
    for (unsigned i = codeBlock->numberOfExceptionHandlers(); i--;) {
        out.append(codeBlock->exceptionHandler(i).target);
        out.append(codeBlock->exceptionHandler(i).start);
        out.append(codeBlock->exceptionHandler(i).end);
    }

    for (unsigned bytecodeOffset = 0; bytecodeOffset < instructionCount;) {
        OpcodeID opcodeID = Interpreter::getOpcodeID(instructionsBegin[bytecodeOffset]);
        getJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, out);
        bytecodeOffset += opcodeLengths[opcodeID];
    }
    
    std::sort(out.begin(), out.end());
    
    // We will have duplicates, and we must remove them.
    unsigned toIndex = 0;
    unsigned fromIndex = 0;
    unsigned lastValue = UINT_MAX;
    while (fromIndex < out.size()) {
        unsigned value = out[fromIndex++];
        if (value == lastValue)
            continue;
        out[toIndex++] = value;
        lastValue = value;
    }
    out.shrinkCapacity(toIndex);
}

void computePreciseJumpTargets(CodeBlock* codeBlock, Vector<unsigned, 32>& out)
{
    computePreciseJumpTargetsInternal<ComputePreciseJumpTargetsMode::FollowCodeBlockClaim>(codeBlock, codeBlock->instructions().begin(), codeBlock->instructions().size(), out);
}

void computePreciseJumpTargets(CodeBlock* codeBlock, Instruction* instructionsBegin, unsigned instructionCount, Vector<unsigned, 32>& out)
{
    computePreciseJumpTargetsInternal<ComputePreciseJumpTargetsMode::FollowCodeBlockClaim>(codeBlock, instructionsBegin, instructionCount, out);
}

void computePreciseJumpTargets(UnlinkedCodeBlock* codeBlock, UnlinkedInstruction* instructionsBegin, unsigned instructionCount, Vector<unsigned, 32>& out)
{
    computePreciseJumpTargetsInternal<ComputePreciseJumpTargetsMode::FollowCodeBlockClaim>(codeBlock, instructionsBegin, instructionCount, out);
}

void recomputePreciseJumpTargets(UnlinkedCodeBlock* codeBlock, UnlinkedInstruction* instructionsBegin, unsigned instructionCount, Vector<unsigned>& out)
{
    computePreciseJumpTargetsInternal<ComputePreciseJumpTargetsMode::ForceCompute>(codeBlock, instructionsBegin, instructionCount, out);
}

void findJumpTargetsForBytecodeOffset(CodeBlock* codeBlock, Instruction* instructionsBegin, unsigned bytecodeOffset, Vector<unsigned, 1>& out)
{
    getJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, out);
}

void findJumpTargetsForBytecodeOffset(UnlinkedCodeBlock* codeBlock, UnlinkedInstruction* instructionsBegin, unsigned bytecodeOffset, Vector<unsigned, 1>& out)
{
    getJumpTargetsForBytecodeOffset(codeBlock, instructionsBegin, bytecodeOffset, out);
}

} // namespace JSC