C++ emitLoad函数代码示例

void JIT::emit_op_ret_object_or_this(Instruction* currentInstruction)
{
    unsigned result = currentInstruction[1].u.operand;
    unsigned thisReg = currentInstruction[2].u.operand;

    // We could JIT generate the deref, only calling out to C when the refcount hits zero.
    if (m_codeBlock->needsFullScopeChain())
        JITStubCall(this, cti_op_ret_scopeChain).call();

    emitLoad(result, regT1, regT0);
    Jump notJSCell = branch32(NotEqual, regT1, Imm32(JSValue::CellTag));
    loadPtr(Address(regT0, OBJECT_OFFSETOF(JSCell, m_structure)), regT2);
    Jump notObject = branch8(NotEqual, Address(regT2, OBJECT_OFFSETOF(Structure, m_typeInfo) + OBJECT_OFFSETOF(TypeInfo, m_type)), Imm32(ObjectType));

    emitGetFromCallFrameHeaderPtr(RegisterFile::ReturnPC, regT2);
    emitGetFromCallFrameHeaderPtr(RegisterFile::CallerFrame, callFrameRegister);

    restoreReturnAddressBeforeReturn(regT2);
    ret();

    notJSCell.link(this);
    notObject.link(this);
    emitLoad(thisReg, regT1, regT0);

    emitGetFromCallFrameHeaderPtr(RegisterFile::ReturnPC, regT2);
    emitGetFromCallFrameHeaderPtr(RegisterFile::CallerFrame, callFrameRegister);

    restoreReturnAddressBeforeReturn(regT2);
    ret();
}

void JIT::compileSetupVarargsFrame(Instruction* instruction, CallLinkInfo* info)
{
    int thisValue = instruction[3].u.operand;
    int arguments = instruction[4].u.operand;
    int firstFreeRegister = instruction[5].u.operand;
    int firstVarArgOffset = instruction[6].u.operand;

    emitLoad(arguments, regT1, regT0);
    callOperation(operationSizeFrameForVarargs, regT1, regT0, -firstFreeRegister, firstVarArgOffset);
    move(TrustedImm32(-firstFreeRegister), regT1);
    emitSetVarargsFrame(*this, returnValueGPR, false, regT1, regT1);
    addPtr(TrustedImm32(-(sizeof(CallerFrameAndPC) + WTF::roundUpToMultipleOf(stackAlignmentBytes(), 6 * sizeof(void*)))), regT1, stackPointerRegister);
    emitLoad(arguments, regT2, regT4);
    callOperation(operationSetupVarargsFrame, regT1, regT2, regT4, firstVarArgOffset, regT0);
    move(returnValueGPR, regT1);

    // Profile the argument count.
    load32(Address(regT1, JSStack::ArgumentCount * static_cast<int>(sizeof(Register)) + PayloadOffset), regT2);
    load8(info->addressOfMaxNumArguments(), regT0);
    Jump notBiggest = branch32(Above, regT0, regT2);
    Jump notSaturated = branch32(BelowOrEqual, regT2, TrustedImm32(255));
    move(TrustedImm32(255), regT2);
    notSaturated.link(this);
    store8(regT2, info->addressOfMaxNumArguments());
    notBiggest.link(this);
    
    // Initialize 'this'.
    emitLoad(thisValue, regT2, regT0);
    store32(regT0, Address(regT1, PayloadOffset + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
    store32(regT2, Address(regT1, TagOffset + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
    
    addPtr(TrustedImm32(sizeof(CallerFrameAndPC)), regT1, stackPointerRegister);
}

void JIT::compileOpCall(OpcodeID opcodeID, Instruction* instruction, unsigned)
{
    int callee = instruction[1].u.operand;
    int argCount = instruction[2].u.operand;
    int registerOffset = instruction[3].u.operand;

    Jump wasEval;
    if (opcodeID == op_call_eval) {
        JITStubCall stubCall(this, cti_op_call_eval);
        stubCall.addArgument(callee);
        stubCall.addArgument(JIT::Imm32(registerOffset));
        stubCall.addArgument(JIT::Imm32(argCount));
        stubCall.call();
        wasEval = branch32(NotEqual, regT1, TrustedImm32(JSValue::EmptyValueTag));
    }

    emitLoad(callee, regT1, regT0);

    emitJumpSlowCaseIfNotJSCell(callee, regT1);
    addSlowCase(branchPtr(NotEqual, Address(regT0), TrustedImmPtr(m_globalData->jsFunctionVPtr)));

    // Speculatively roll the callframe, assuming argCount will match the arity.
    store32(TrustedImm32(JSValue::CellTag), tagFor(RegisterFile::CallerFrame + registerOffset, callFrameRegister));
    storePtr(callFrameRegister, payloadFor(RegisterFile::CallerFrame + registerOffset, callFrameRegister));
    addPtr(Imm32(registerOffset * static_cast<int>(sizeof(Register))), callFrameRegister);
    move(TrustedImm32(argCount), regT1);

    emitNakedCall(opcodeID == op_construct ? m_globalData->jitStubs->ctiVirtualConstruct() : m_globalData->jitStubs->ctiVirtualCall());

    if (opcodeID == op_call_eval)
        wasEval.link(this);

    sampleCodeBlock(m_codeBlock);
}

void JIT::compileOpCallVarargs(Instruction* instruction)
{
    int callee = instruction[1].u.operand;
    int argCountRegister = instruction[2].u.operand;
    int registerOffset = instruction[3].u.operand;

    emitLoad(callee, regT1, regT0);
    emitLoadPayload(argCountRegister, regT2); // argCount
    addPtr(Imm32(registerOffset), regT2, regT3); // registerOffset

    emitJumpSlowCaseIfNotJSCell(callee, regT1);
    addSlowCase(branchPtr(NotEqual, Address(regT0), TrustedImmPtr(m_globalData->jsFunctionVPtr)));

    // Speculatively roll the callframe, assuming argCount will match the arity.
    mul32(TrustedImm32(sizeof(Register)), regT3, regT3);
    addPtr(callFrameRegister, regT3);
    store32(TrustedImm32(JSValue::CellTag), tagFor(RegisterFile::CallerFrame, regT3));
    storePtr(callFrameRegister, payloadFor(RegisterFile::CallerFrame, regT3));
    move(regT3, callFrameRegister);

    move(regT2, regT1); // argCount

    emitNakedCall(m_globalData->jitStubs->ctiVirtualCall());

    sampleCodeBlock(m_codeBlock);
}

void JIT::compileCallEvalSlowCase(Instruction* instruction, Vector<SlowCaseEntry>::iterator& iter)
{
    CallLinkInfo* info = m_codeBlock->addCallLinkInfo();
    info->setUpCall(CallLinkInfo::Call, CodeOrigin(m_bytecodeOffset), regT0);

    linkSlowCase(iter);

    int registerOffset = -instruction[4].u.operand;

    addPtr(TrustedImm32(registerOffset * sizeof(Register) + sizeof(CallerFrameAndPC)), callFrameRegister, stackPointerRegister);

    loadPtr(Address(stackPointerRegister, sizeof(Register) * JSStack::Callee - sizeof(CallerFrameAndPC)), regT0);
    loadPtr(Address(stackPointerRegister, sizeof(Register) * JSStack::Callee - sizeof(CallerFrameAndPC)), regT1);
    move(TrustedImmPtr(info), regT2);

    emitLoad(JSStack::Callee, regT1, regT0);
    MacroAssemblerCodeRef virtualThunk = virtualThunkFor(m_vm, *info);
    info->setSlowStub(createJITStubRoutine(virtualThunk, *m_vm, nullptr, true));
    emitNakedCall(virtualThunk.code());
    addPtr(TrustedImm32(stackPointerOffsetFor(m_codeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);
    checkStackPointerAlignment();

    sampleCodeBlock(m_codeBlock);
    
    emitPutCallResult(instruction);
}

void JIT::compileOpCall(OpcodeID opcodeID, Instruction* instruction, unsigned callLinkInfoIndex)
{
    int callee = instruction[1].u.operand;

    /* Caller always:
        - Updates callFrameRegister to callee callFrame.
        - Initializes ArgumentCount; CallerFrame; Callee.

       For a JS call:
        - Caller initializes ScopeChain.
        - Callee initializes ReturnPC; CodeBlock.
        - Callee restores callFrameRegister before return.

       For a non-JS call:
        - Caller initializes ScopeChain; ReturnPC; CodeBlock.
        - Caller restores callFrameRegister after return.
    */
    
    if (opcodeID == op_call_varargs)
        compileLoadVarargs(instruction);
    else {
        int argCount = instruction[2].u.operand;
        int registerOffset = instruction[3].u.operand;

        addPtr(TrustedImm32(registerOffset * sizeof(Register)), callFrameRegister, regT3);

        store32(TrustedImm32(argCount), payloadFor(RegisterFile::ArgumentCount, regT3));
    } // regT3 holds newCallFrame with ArgumentCount initialized.
    emitLoad(callee, regT1, regT0); // regT1, regT0 holds callee.

    storePtr(callFrameRegister, Address(regT3, RegisterFile::CallerFrame * static_cast<int>(sizeof(Register))));
    emitStore(RegisterFile::Callee, regT1, regT0, regT3);
    move(regT3, callFrameRegister);

    if (opcodeID == op_call_eval) {
        compileCallEval();
        return;
    }

    DataLabelPtr addressOfLinkedFunctionCheck;
    BEGIN_UNINTERRUPTED_SEQUENCE(sequenceOpCall);
    Jump slowCase = branchPtrWithPatch(NotEqual, regT0, addressOfLinkedFunctionCheck, TrustedImmPtr(0));
    END_UNINTERRUPTED_SEQUENCE(sequenceOpCall);

    addSlowCase(slowCase);
    addSlowCase(branch32(NotEqual, regT1, TrustedImm32(JSValue::CellTag)));

    ASSERT_JIT_OFFSET(differenceBetween(addressOfLinkedFunctionCheck, slowCase), patchOffsetOpCallCompareToJump);
    ASSERT(m_callStructureStubCompilationInfo.size() == callLinkInfoIndex);
    m_callStructureStubCompilationInfo.append(StructureStubCompilationInfo());
    m_callStructureStubCompilationInfo[callLinkInfoIndex].hotPathBegin = addressOfLinkedFunctionCheck;
    m_callStructureStubCompilationInfo[callLinkInfoIndex].callType = CallLinkInfo::callTypeFor(opcodeID);
    m_callStructureStubCompilationInfo[callLinkInfoIndex].bytecodeIndex = m_bytecodeOffset;

    loadPtr(Address(regT0, OBJECT_OFFSETOF(JSFunction, m_scopeChain)), regT1);
    emitPutCellToCallFrameHeader(regT1, RegisterFile::ScopeChain);
    m_callStructureStubCompilationInfo[callLinkInfoIndex].hotPathOther = emitNakedCall();

    sampleCodeBlock(m_codeBlock);
}

void JIT::compileLoadVarargs(Instruction* instruction)
{
    int thisValue = instruction[2].u.operand;
    int arguments = instruction[3].u.operand;
    int firstFreeRegister = instruction[4].u.operand;

    JumpList slowCase;
    JumpList end;
    if (m_codeBlock->usesArguments() && arguments == m_codeBlock->argumentsRegister()) {
        emitLoadTag(arguments, regT1);
        slowCase.append(branch32(NotEqual, regT1, TrustedImm32(JSValue::EmptyValueTag)));

        load32(payloadFor(RegisterFile::ArgumentCount), regT2);
        slowCase.append(branch32(Above, regT2, TrustedImm32(Arguments::MaxArguments + 1)));
        // regT2: argumentCountIncludingThis

        move(regT2, regT3);
        add32(TrustedImm32(firstFreeRegister + RegisterFile::CallFrameHeaderSize), regT3);
        lshift32(TrustedImm32(3), regT3);
        addPtr(callFrameRegister, regT3);
        // regT3: newCallFrame

        slowCase.append(branchPtr(Below, AbsoluteAddress(m_globalData->interpreter->registerFile().addressOfEnd()), regT3));

        // Initialize ArgumentCount.
        store32(regT2, payloadFor(RegisterFile::ArgumentCount, regT3));

        // Initialize 'this'.
        emitLoad(thisValue, regT1, regT0);
        store32(regT0, Address(regT3, OBJECT_OFFSETOF(JSValue, u.asBits.payload) + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
        store32(regT1, Address(regT3, OBJECT_OFFSETOF(JSValue, u.asBits.tag) + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));

        // Copy arguments.
        neg32(regT2);
        end.append(branchAdd32(Zero, TrustedImm32(1), regT2));
        // regT2: -argumentCount;

        Label copyLoop = label();
        load32(BaseIndex(callFrameRegister, regT2, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.payload) +(CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))), regT0);
        load32(BaseIndex(callFrameRegister, regT2, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.tag) +(CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))), regT1);
        store32(regT0, BaseIndex(regT3, regT2, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.payload) +(CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
        store32(regT1, BaseIndex(regT3, regT2, TimesEight, OBJECT_OFFSETOF(JSValue, u.asBits.tag) +(CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
        branchAdd32(NonZero, TrustedImm32(1), regT2).linkTo(copyLoop, this);

        end.append(jump());
    }

    if (m_codeBlock->usesArguments() && arguments == m_codeBlock->argumentsRegister())
        slowCase.link(this);

    JITStubCall stubCall(this, cti_op_load_varargs);
    stubCall.addArgument(thisValue);
    stubCall.addArgument(arguments);
    stubCall.addArgument(Imm32(firstFreeRegister));
    stubCall.call(regT3);

    if (m_codeBlock->usesArguments() && arguments == m_codeBlock->argumentsRegister())
        end.link(this);
}

//-----------------------------------------
void println(int expVal)
{
   emitLoad(expVal);
   freeTemp(expVal);
   emitInstruction1("dout");
   emitInstructionSS("ldc", "'\\n'");
   emitInstruction1("aout");
}

void JIT::compileOpCall(OpcodeID opcodeID, Instruction* instruction, unsigned callLinkInfoIndex)
{
    int callee = instruction[1].u.operand;
    int argCount = instruction[2].u.operand;
    int registerOffset = instruction[3].u.operand;

    Jump wasEval;
    if (opcodeID == op_call_eval) {
        JITStubCall stubCall(this, cti_op_call_eval);
        stubCall.addArgument(callee);
        stubCall.addArgument(JIT::Imm32(registerOffset));
        stubCall.addArgument(JIT::Imm32(argCount));
        stubCall.call();
        wasEval = branch32(NotEqual, regT1, TrustedImm32(JSValue::EmptyValueTag));
    }

    emitLoad(callee, regT1, regT0);

    DataLabelPtr addressOfLinkedFunctionCheck;

    BEGIN_UNINTERRUPTED_SEQUENCE(sequenceOpCall);

    Jump jumpToSlow = branchPtrWithPatch(NotEqual, regT0, addressOfLinkedFunctionCheck, TrustedImmPtr(0));

    END_UNINTERRUPTED_SEQUENCE(sequenceOpCall);

    addSlowCase(jumpToSlow);
    ASSERT_JIT_OFFSET(differenceBetween(addressOfLinkedFunctionCheck, jumpToSlow), patchOffsetOpCallCompareToJump);
    ASSERT(m_callStructureStubCompilationInfo.size() == callLinkInfoIndex);
    m_callStructureStubCompilationInfo.append(StructureStubCompilationInfo());
    m_callStructureStubCompilationInfo[callLinkInfoIndex].hotPathBegin = addressOfLinkedFunctionCheck;
    m_callStructureStubCompilationInfo[callLinkInfoIndex].isCall = opcodeID != op_construct;
    m_callStructureStubCompilationInfo[callLinkInfoIndex].bytecodeIndex = m_bytecodeOffset;

    addSlowCase(branch32(NotEqual, regT1, TrustedImm32(JSValue::CellTag)));

    // The following is the fast case, only used whan a callee can be linked.

    // Fast version of stack frame initialization, directly relative to edi.
    // Note that this omits to set up RegisterFile::CodeBlock, which is set in the callee
    loadPtr(Address(regT0, OBJECT_OFFSETOF(JSFunction, m_scopeChain)), regT2);

    store32(TrustedImm32(JSValue::Int32Tag), tagFor(registerOffset + RegisterFile::ArgumentCount));
    store32(Imm32(argCount), payloadFor(registerOffset + RegisterFile::ArgumentCount));
    storePtr(callFrameRegister, payloadFor(RegisterFile::CallerFrame + registerOffset, callFrameRegister));
    emitStore(registerOffset + RegisterFile::Callee, regT1, regT0);
    store32(TrustedImm32(JSValue::CellTag), tagFor(registerOffset + RegisterFile::ScopeChain));
    store32(regT2, payloadFor(registerOffset + RegisterFile::ScopeChain));
    addPtr(Imm32(registerOffset * sizeof(Register)), callFrameRegister);

    // Call to the callee
    m_callStructureStubCompilationInfo[callLinkInfoIndex].hotPathOther = emitNakedCall();
    
    if (opcodeID == op_call_eval)
        wasEval.link(this);

    sampleCodeBlock(m_codeBlock);
}

std::enable_if_t<
    Op::opcodeID == op_call_varargs || Op::opcodeID == op_construct_varargs
    || Op::opcodeID == op_tail_call_varargs || Op::opcodeID == op_tail_call_forward_arguments
, void>
JIT::compileSetupFrame(const Op& bytecode, CallLinkInfo* info)
{
    OpcodeID opcodeID = Op::opcodeID;
    int thisValue = bytecode.m_thisValue.offset();
    int arguments = bytecode.m_arguments.offset();
    int firstFreeRegister = bytecode.m_firstFree.offset();
    int firstVarArgOffset = bytecode.m_firstVarArg;

    emitLoad(arguments, regT1, regT0);
    Z_JITOperation_EJZZ sizeOperation;
    if (Op::opcodeID == op_tail_call_forward_arguments)
        sizeOperation = operationSizeFrameForForwardArguments;
    else
        sizeOperation = operationSizeFrameForVarargs;
    callOperation(sizeOperation, JSValueRegs(regT1, regT0), -firstFreeRegister, firstVarArgOffset);
    move(TrustedImm32(-firstFreeRegister), regT1);
    emitSetVarargsFrame(*this, returnValueGPR, false, regT1, regT1);
    addPtr(TrustedImm32(-(sizeof(CallerFrameAndPC) + WTF::roundUpToMultipleOf(stackAlignmentBytes(), 6 * sizeof(void*)))), regT1, stackPointerRegister);
    emitLoad(arguments, regT2, regT4);
    F_JITOperation_EFJZZ setupOperation;
    if (opcodeID == op_tail_call_forward_arguments)
        setupOperation = operationSetupForwardArgumentsFrame;
    else
        setupOperation = operationSetupVarargsFrame;
    callOperation(setupOperation, regT1, JSValueRegs(regT2, regT4), firstVarArgOffset, regT0);
    move(returnValueGPR, regT1);

    // Profile the argument count.
    load32(Address(regT1, CallFrameSlot::argumentCount * static_cast<int>(sizeof(Register)) + PayloadOffset), regT2);
    load32(info->addressOfMaxNumArguments(), regT0);
    Jump notBiggest = branch32(Above, regT0, regT2);
    store32(regT2, info->addressOfMaxNumArguments());
    notBiggest.link(this);
    
    // Initialize 'this'.
    emitLoad(thisValue, regT2, regT0);
    store32(regT0, Address(regT1, PayloadOffset + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
    store32(regT2, Address(regT1, TagOffset + (CallFrame::thisArgumentOffset() * static_cast<int>(sizeof(Register)))));
    
    addPtr(TrustedImm32(sizeof(CallerFrameAndPC)), regT1, stackPointerRegister);
}

void JIT::compileCallEvalSlowCase(Vector<SlowCaseEntry>::iterator& iter)
{
    linkSlowCase(iter);

    emitLoad(JSStack::Callee, regT1, regT0);
    emitNakedCall(m_globalData->getCTIStub(virtualCallGenerator).code());

    sampleCodeBlock(m_codeBlock);
}

void JIT::compileCallEvalSlowCase(Vector<SlowCaseEntry>::iterator& iter)
{
    linkSlowCase(iter);

    emitLoad(RegisterFile::Callee, regT1, regT0);
    emitNakedCall(m_globalData->jitStubs->ctiVirtualCall());

    sampleCodeBlock(m_codeBlock);
}

//-----------------------------------------
int mult(int left, int right)
{
   int temp;
   emitLoad(left);
   emitInstructionSI("mult", right);
   freeTemp(left);
   freeTemp(right);
   temp = getTemp();
   emitInstructionSI("st", temp);
   return temp;
}

void JIT::compileCallEvalSlowCase(Instruction* instruction, Vector<SlowCaseEntry>::iterator& iter)
{
    linkSlowCase(iter);

    int registerOffset = -instruction[4].u.operand;

    addPtr(TrustedImm32(registerOffset * sizeof(Register) + sizeof(CallerFrameAndPC)), callFrameRegister, stackPointerRegister);

    loadPtr(Address(stackPointerRegister, sizeof(Register) * JSStack::Callee - sizeof(CallerFrameAndPC)), regT0);
    loadPtr(Address(stackPointerRegister, sizeof(Register) * JSStack::Callee - sizeof(CallerFrameAndPC)), regT1);
    move(TrustedImmPtr(&CallLinkInfo::dummy()), regT2);

    emitLoad(JSStack::Callee, regT1, regT0);
    emitNakedCall(m_vm->getCTIStub(virtualCallThunkGenerator).code());
    addPtr(TrustedImm32(stackPointerOffsetFor(m_codeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);
    checkStackPointerAlignment();

    sampleCodeBlock(m_codeBlock);
    
    emitPutCallResult(instruction);
}

void JIT::compileCallEvalSlowCase(const Instruction* instruction, Vector<SlowCaseEntry>::iterator& iter)
{
    linkAllSlowCases(iter);

    auto bytecode = instruction->as<OpCallEval>();
    CallLinkInfo* info = m_codeBlock->addCallLinkInfo();
    info->setUpCall(CallLinkInfo::Call, CodeOrigin(m_bytecodeOffset), regT0);

    int registerOffset = -bytecode.m_argv;
    int callee = bytecode.m_callee.offset();

    addPtr(TrustedImm32(registerOffset * sizeof(Register) + sizeof(CallerFrameAndPC)), callFrameRegister, stackPointerRegister);

    emitLoad(callee, regT1, regT0);
    emitDumbVirtualCall(*vm(), info);
    addPtr(TrustedImm32(stackPointerOffsetFor(m_codeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);
    checkStackPointerAlignment();

    sampleCodeBlock(m_codeBlock);
    
    emitPutCallResult(bytecode);
}