Source/JavaScriptCore/jit/JITOpcodes.cpp

/*
 * Copyright (C) 2009-2021 Apple Inc. All rights reserved.
 * Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com>
 *
 * 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. ``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
 * 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"
#if ENABLE(JIT)
#include "JIT.h"

#include "BasicBlockLocation.h"
#include "BytecodeGenerator.h"
#include "Exception.h"
#include "JITInlines.h"
#include "JITThunks.h"
#include "JSCast.h"
#include "JSFunction.h"
#include "JSPropertyNameEnumerator.h"
#include "LinkBuffer.h"
#include "SuperSampler.h"
#include "ThunkGenerators.h"
#include "TypeLocation.h"
#include "TypeProfilerLog.h"
#include "VirtualRegister.h"

namespace JSC {

#if USE(JSVALUE64)

void JIT::emit_op_mov(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpMov>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src = bytecode.m_src;

    if (src.isConstant()) {
        if (m_profiledCodeBlock->isConstantOwnedByUnlinkedCodeBlock(src)) {
            JSValue value = m_unlinkedCodeBlock->getConstant(src);
            store64(Imm64(JSValue::encode(value)), addressFor(dst));
        } else {
            loadCodeBlockConstant(src, regT0);
            store64(regT0, addressFor(dst));
        }

        return;
    }

    load64(addressFor(src), regT0);
    store64(regT0, addressFor(dst));
}


void JIT::emit_op_end(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpEnd>();
    RELEASE_ASSERT(returnValueGPR != callFrameRegister);
    emitGetVirtualRegister(bytecode.m_value, returnValueGPR);
    emitRestoreCalleeSaves();
    emitFunctionEpilogue();
    ret();
}

void JIT::emit_op_jmp(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJmp>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    addJump(jump(), target);
}

void JIT::emit_op_new_object(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNewObject>();

    RegisterID resultReg = regT0;
    RegisterID allocatorReg = regT1;
    RegisterID scratchReg = regT2;
    RegisterID structureReg = regT3;

    loadPtrFromMetadata(bytecode, OpNewObject::Metadata::offsetOfObjectAllocationProfile() + ObjectAllocationProfile::offsetOfAllocator(), allocatorReg);
    loadPtrFromMetadata(bytecode, OpNewObject::Metadata::offsetOfObjectAllocationProfile() + ObjectAllocationProfile::offsetOfStructure(), structureReg);

    JumpList slowCases;
    auto butterfly = TrustedImmPtr(nullptr);
    emitAllocateJSObject(resultReg, JITAllocator::variable(), allocatorReg, structureReg, butterfly, scratchReg, slowCases);
    load8(Address(structureReg, Structure::inlineCapacityOffset()), scratchReg);
    emitInitializeInlineStorage(resultReg, scratchReg);
    mutatorFence(*m_vm);
    emitPutVirtualRegister(bytecode.m_dst);

    addSlowCase(slowCases);
}

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

    RegisterID structureReg = regT3;

    auto bytecode = currentInstruction->as<OpNewObject>();
    VirtualRegister dst = bytecode.m_dst;
    callOperationNoExceptionCheck(operationNewObject, &vm(), structureReg);
    emitStoreCell(dst, returnValueGPR);
}

void JIT::emit_op_overrides_has_instance(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpOverridesHasInstance>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister constructor = bytecode.m_constructor;
    VirtualRegister hasInstanceValue = bytecode.m_hasInstanceValue;

    emitGetVirtualRegister(hasInstanceValue, regT0);

    // We don't jump if we know what Symbol.hasInstance would do.
    loadGlobalObject(regT1);
    Jump customhasInstanceValue = branchPtr(NotEqual, regT0, Address(regT1, OBJECT_OFFSETOF(JSGlobalObject, m_functionProtoHasInstanceSymbolFunction)));

    emitGetVirtualRegister(constructor, regT0);

    // Check that constructor 'ImplementsDefaultHasInstance' i.e. the object is not a C-API user nor a bound function.
    test8(Zero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(ImplementsDefaultHasInstance), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    Jump done = jump();

    customhasInstanceValue.link(this);
    move(TrustedImm32(JSValue::ValueTrue), regT0);

    done.link(this);
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_instanceof(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpInstanceof>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_value;
    VirtualRegister proto = bytecode.m_prototype;

    constexpr GPRReg valueGPR = BaselineInstanceofRegisters::value;
    constexpr GPRReg protoGPR = BaselineInstanceofRegisters::proto;
    constexpr GPRReg resultGPR = BaselineInstanceofRegisters::result;
    constexpr GPRReg stubInfoGPR = BaselineInstanceofRegisters::stubInfo;

    emitGetVirtualRegister(value, valueGPR);
    emitGetVirtualRegister(proto, protoGPR);
    
    // Check that proto are cells. baseVal must be a cell - this is checked by the get_by_id for Symbol.hasInstance.
    emitJumpSlowCaseIfNotJSCell(valueGPR, value);
    emitJumpSlowCaseIfNotJSCell(protoGPR, proto);

    JITInstanceOfGenerator gen(
        nullptr, JITType::BaselineJIT, CodeOrigin(m_bytecodeIndex), CallSiteIndex(m_bytecodeIndex),
        RegisterSet::stubUnavailableRegisters(),
        resultGPR,
        valueGPR,
        protoGPR,
        stubInfoGPR,
        BaselineInstanceofRegisters::scratch1, BaselineInstanceofRegisters::scratch2);

    UnlinkedStructureStubInfo* stubInfo = m_unlinkedStubInfos.add();
    stubInfo->accessType = AccessType::InstanceOf;
    stubInfo->bytecodeIndex = m_bytecodeIndex;
    JITConstantPool::Constant stubInfoIndex = addToConstantPool(JITConstantPool::Type::StructureStubInfo, stubInfo);
    gen.m_unlinkedStubInfoConstantIndex = stubInfoIndex;
    gen.m_unlinkedStubInfo = stubInfo;

    gen.generateBaselineDataICFastPath(*this, stubInfoIndex, stubInfoGPR);
    addSlowCase();
    m_instanceOfs.append(gen);

    emitPutVirtualRegister(dst);
}

void JIT::emitSlow_op_instanceof(const Instruction* currentInstruction, Vector<SlowCaseEntry>::iterator& iter)
{
    linkAllSlowCases(iter);
    
    auto bytecode = currentInstruction->as<OpInstanceof>();
    VirtualRegister resultVReg = bytecode.m_dst;
    
    JITInstanceOfGenerator& gen = m_instanceOfs[m_instanceOfIndex++];
    
    Label coldPathBegin = label();

    static_assert(BaselineInstanceofRegisters::stubInfo == argumentGPR1);
    static_assert(BaselineInstanceofRegisters::value == argumentGPR2);
    static_assert(BaselineInstanceofRegisters::proto == argumentGPR3);
    loadGlobalObject(argumentGPR0);
    loadConstant(gen.m_unlinkedStubInfoConstantIndex, argumentGPR1);
    callOperation<decltype(operationInstanceOfOptimize)>(Address(argumentGPR1, StructureStubInfo::offsetOfSlowOperation()), resultVReg, argumentGPR0, argumentGPR1, argumentGPR2, argumentGPR3);
    gen.reportSlowPathCall(coldPathBegin, Call());
}

void JIT::emit_op_instanceof_custom(const Instruction*)
{
    // This always goes to slow path since we expect it to be rare.
    addSlowCase(jump());
}
    
void JIT::emit_op_is_empty(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsEmpty>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;

    emitGetVirtualRegister(value, regT0);
    compare64(Equal, regT0, TrustedImm32(JSValue::encode(JSValue())), regT0);

    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_typeof_is_undefined(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpTypeofIsUndefined>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;
    
    emitGetVirtualRegister(value, regT0);
    Jump isCell = branchIfCell(regT0);

    compare64(Equal, regT0, TrustedImm32(JSValue::ValueUndefined), regT0);
    Jump done = jump();
    
    isCell.link(this);
    Jump isMasqueradesAsUndefined = branchTest8(NonZero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(MasqueradesAsUndefined));
    move(TrustedImm32(0), regT0);
    Jump notMasqueradesAsUndefined = jump();

    isMasqueradesAsUndefined.link(this);
    emitLoadStructure(vm(), regT0, regT1, regT2);
    loadGlobalObject(regT0);
    loadPtr(Address(regT1, Structure::globalObjectOffset()), regT1);
    comparePtr(Equal, regT0, regT1, regT0);

    notMasqueradesAsUndefined.link(this);
    done.link(this);
    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_is_undefined_or_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsUndefinedOrNull>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;

    emitGetVirtualRegister(value, regT0);

    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    compare64(Equal, regT0, TrustedImm32(JSValue::ValueNull), regT0);

    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_is_boolean(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsBoolean>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;
    
    emitGetVirtualRegister(value, regT0);
    xor64(TrustedImm32(JSValue::ValueFalse), regT0);
    test64(Zero, regT0, TrustedImm32(static_cast<int32_t>(~1)), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_is_number(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsNumber>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;
    
    emitGetVirtualRegister(value, regT0);
    test64(NonZero, regT0, numberTagRegister, regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

#if USE(BIGINT32)
void JIT::emit_op_is_big_int(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsBigInt>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;

    emitGetVirtualRegister(value, regT0);
    Jump isCell = branchIfCell(regT0);

    move(TrustedImm64(JSValue::BigInt32Mask), regT1);
    and64(regT1, regT0);
    compare64(Equal, regT0, TrustedImm32(JSValue::BigInt32Tag), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    Jump done = jump();

    isCell.link(this);
    compare8(Equal, Address(regT0, JSCell::typeInfoTypeOffset()), TrustedImm32(HeapBigIntType), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });

    done.link(this);
    emitPutVirtualRegister(dst);
}
#else // if !USE(BIGINT32)
NO_RETURN void JIT::emit_op_is_big_int(const Instruction*)
{
    // If we only have HeapBigInts, then we emit isCellWithType instead of isBigInt.
    RELEASE_ASSERT_NOT_REACHED();
}
#endif

void JIT::emit_op_is_cell_with_type(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsCellWithType>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;
    int type = bytecode.m_type;

    emitGetVirtualRegister(value, regT0);
    Jump isNotCell = branchIfNotCell(regT0);

    compare8(Equal, Address(regT0, JSCell::typeInfoTypeOffset()), TrustedImm32(type), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    Jump done = jump();

    isNotCell.link(this);
    move(TrustedImm32(JSValue::ValueFalse), regT0);

    done.link(this);
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_is_object(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpIsObject>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_operand;

    emitGetVirtualRegister(value, regT0);
    Jump isNotCell = branchIfNotCell(regT0);

    compare8(AboveOrEqual, Address(regT0, JSCell::typeInfoTypeOffset()), TrustedImm32(ObjectType), regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    Jump done = jump();

    isNotCell.link(this);
    move(TrustedImm32(JSValue::ValueFalse), regT0);

    done.link(this);
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_ret(const Instruction* currentInstruction)
{
    ASSERT(callFrameRegister != regT1);
    ASSERT(regT1 != returnValueGPR);
    ASSERT(returnValueGPR != callFrameRegister);

    // Return the result in %eax.
    auto bytecode = currentInstruction->as<OpRet>();
    emitGetVirtualRegister(bytecode.m_value, returnValueGPR);

#if !ENABLE(EXTRA_CTI_THUNKS)
    checkStackPointerAlignment();
    emitRestoreCalleeSaves();
    emitFunctionEpilogue();
    ret();
#else
    emitNakedNearJump(vm().getCTIStub(op_ret_handlerGenerator).code());
#endif
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::op_ret_handlerGenerator(VM&)
{
    CCallHelpers jit;

    jit.checkStackPointerAlignment();
    jit.emitRestoreCalleeSavesFor(&RegisterAtOffsetList::llintBaselineCalleeSaveRegisters());
    jit.emitFunctionEpilogue();
    jit.ret();

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::ExtraCTIThunk);
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: op_ret_handler");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

void JIT::emit_op_to_primitive(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToPrimitive>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src = bytecode.m_src;

    emitGetVirtualRegister(src, regT0);
    
    Jump isImm = branchIfNotCell(regT0);
    addSlowCase(branchIfObject(regT0));
    isImm.link(this);

    if (dst != src)
        emitPutVirtualRegister(dst);
}

void JIT::emit_op_to_property_key(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToPropertyKey>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src = bytecode.m_src;

    emitGetVirtualRegister(src, regT0);

    addSlowCase(branchIfNotCell(regT0));
    Jump done = branchIfSymbol(regT0);
    addSlowCase(branchIfNotString(regT0));

    done.link(this);
    if (src != dst)
        emitPutVirtualRegister(dst);
}

void JIT::emit_op_set_function_name(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpSetFunctionName>();
    emitGetVirtualRegister(bytecode.m_function, argumentGPR1);
    emitGetVirtualRegister(bytecode.m_name, argumentGPR2);
    loadGlobalObject(argumentGPR0);
    callOperation(operationSetFunctionName, argumentGPR0, argumentGPR1, argumentGPR2);
}

void JIT::emit_op_not(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNot>();
    emitGetVirtualRegister(bytecode.m_operand, regT0);

    // Invert against JSValue(false); if the value was tagged as a boolean, then all bits will be
    // clear other than the low bit (which will be 0 or 1 for false or true inputs respectively).
    // Then invert against JSValue(true), which will add the tag back in, and flip the low bit.
    xor64(TrustedImm32(JSValue::ValueFalse), regT0);
    addSlowCase(branchTestPtr(NonZero, regT0, TrustedImm32(static_cast<int32_t>(~1))));
    xor64(TrustedImm32(JSValue::ValueTrue), regT0);

    emitPutVirtualRegister(bytecode.m_dst);
}

void JIT::emit_op_jfalse(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJfalse>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    constexpr GPRReg value = regT0;

    emitGetVirtualRegister(bytecode.m_condition, value);
#if !ENABLE(EXTRA_CTI_THUNKS)
    constexpr GPRReg scratch1 = regT1;
    constexpr GPRReg scratch2 = regT2;
    constexpr GPRReg globalObjectGPR = regT3;
    constexpr bool shouldCheckMasqueradesAsUndefined = true;
    loadGlobalObject(globalObjectGPR);
    addJump(branchIfFalsey(vm(), JSValueRegs(value), scratch1, scratch2, fpRegT0, fpRegT1, shouldCheckMasqueradesAsUndefined, globalObjectGPR), target);
#else
    emitNakedNearCall(vm().getCTIStub(valueIsFalseyGenerator).retaggedCode<NoPtrTag>());
    addJump(branchTest32(NonZero, regT0), target);
#endif
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::valueIsFalseyGenerator(VM& vm)
{
    // The thunk generated by this function can only work with the LLInt / Baseline JIT because
    // it makes assumptions about the right globalObject being available from CallFrame::codeBlock().
    // DFG/FTL may inline functions belonging to other globalObjects, which may not match
    // CallFrame::codeBlock().
    CCallHelpers jit;

    constexpr GPRReg value = regT0;
    constexpr GPRReg scratch1 = regT1;
    constexpr GPRReg scratch2 = regT2;
    constexpr bool shouldCheckMasqueradesAsUndefined = true;

    jit.tagReturnAddress();

    constexpr GPRReg globalObjectGPR = regT3;
    jit.loadPtr(addressFor(CallFrameSlot::codeBlock), globalObjectGPR);
    jit.loadPtr(Address(globalObjectGPR, CodeBlock::offsetOfGlobalObject()), globalObjectGPR);
    auto isFalsey = jit.branchIfFalsey(vm, JSValueRegs(value), scratch1, scratch2, fpRegT0, fpRegT1, shouldCheckMasqueradesAsUndefined, globalObjectGPR);
    jit.move(TrustedImm32(0), regT0);
    Jump done = jit.jump();

    isFalsey.link(&jit);
    jit.move(TrustedImm32(1), regT0);

    done.link(&jit);
    jit.ret();

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::Thunk);
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: valueIsfalsey");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

void JIT::emit_op_jeq_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJeqNull>();
    VirtualRegister src = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    emitGetVirtualRegister(src, regT0);
    Jump isImmediate = branchIfNotCell(regT0);

    // First, handle JSCell cases - check MasqueradesAsUndefined bit on the structure.
    Jump isNotMasqueradesAsUndefined = branchTest8(Zero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(MasqueradesAsUndefined));
    emitLoadStructure(vm(), regT0, regT2, regT1);
    loadGlobalObject(regT0);
    addJump(branchPtr(Equal, Address(regT2, Structure::globalObjectOffset()), regT0), target);
    Jump masqueradesGlobalObjectIsForeign = jump();

    // Now handle the immediate cases - undefined & null
    isImmediate.link(this);
    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    addJump(branch64(Equal, regT0, TrustedImm64(JSValue::encode(jsNull()))), target);            

    isNotMasqueradesAsUndefined.link(this);
    masqueradesGlobalObjectIsForeign.link(this);
};
void JIT::emit_op_jneq_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJneqNull>();
    VirtualRegister src = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    emitGetVirtualRegister(src, regT0);
    Jump isImmediate = branchIfNotCell(regT0);

    // First, handle JSCell cases - check MasqueradesAsUndefined bit on the structure.
    addJump(branchTest8(Zero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(MasqueradesAsUndefined)), target);
    emitLoadStructure(vm(), regT0, regT2, regT1);
    loadGlobalObject(regT0);
    addJump(branchPtr(NotEqual, Address(regT2, Structure::globalObjectOffset()), regT0), target);
    Jump wasNotImmediate = jump();

    // Now handle the immediate cases - undefined & null
    isImmediate.link(this);
    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    addJump(branch64(NotEqual, regT0, TrustedImm64(JSValue::encode(jsNull()))), target);            

    wasNotImmediate.link(this);
}

void JIT::emit_op_jundefined_or_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJundefinedOrNull>();
    VirtualRegister value = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    emitGetVirtualRegister(value, regT0);

    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    addJump(branch64(Equal, regT0, TrustedImm64(JSValue::encode(jsNull()))), target);
}

void JIT::emit_op_jnundefined_or_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJnundefinedOrNull>();
    VirtualRegister value = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    emitGetVirtualRegister(value, regT0);

    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    addJump(branch64(NotEqual, regT0, TrustedImm64(JSValue::encode(jsNull()))), target);
}

void JIT::emit_op_jeq_ptr(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJeqPtr>();
    VirtualRegister src = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    emitGetVirtualRegister(src, regT0);
    loadCodeBlockConstant(bytecode.m_specialPointer, regT1);
    addJump(branchPtr(Equal, regT0, regT1), target);
}

void JIT::emit_op_jneq_ptr(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJneqPtr>();
    VirtualRegister src = bytecode.m_value;
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    
    emitGetVirtualRegister(src, regT0);
    loadCodeBlockConstant(bytecode.m_specialPointer, regT1);
    CCallHelpers::Jump equal = branchPtr(Equal, regT0, regT1);
    store8ToMetadata(TrustedImm32(1), bytecode, OpJneqPtr::Metadata::offsetOfHasJumped());
    addJump(jump(), target);
    equal.link(this);
}

void JIT::emit_op_eq(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpEq>();
    emitGetVirtualRegisters(bytecode.m_lhs, regT0, bytecode.m_rhs, regT1);
    emitJumpSlowCaseIfNotInt(regT0, regT1, regT2);
    compare32(Equal, regT1, regT0, regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(bytecode.m_dst);
}

void JIT::emit_op_jeq(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJeq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    emitGetVirtualRegisters(bytecode.m_lhs, regT0, bytecode.m_rhs, regT1);
    emitJumpSlowCaseIfNotInt(regT0, regT1, regT2);
    addJump(branch32(Equal, regT0, regT1), target);
}

void JIT::emit_op_jtrue(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJtrue>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);

    constexpr GPRReg value = regT0;

    emitGetVirtualRegister(bytecode.m_condition, value);
#if !ENABLE(EXTRA_CTI_THUNKS)
    constexpr GPRReg scratch1 = regT1;
    constexpr GPRReg scratch2 = regT2;
    constexpr GPRReg globalObjectGPR = regT3;
    constexpr bool shouldCheckMasqueradesAsUndefined = true;
    loadGlobalObject(globalObjectGPR);
    addJump(branchIfTruthy(vm(), JSValueRegs(value), scratch1, scratch2, fpRegT0, fpRegT1, shouldCheckMasqueradesAsUndefined, globalObjectGPR), target);
#else
    emitNakedNearCall(vm().getCTIStub(valueIsTruthyGenerator).retaggedCode<NoPtrTag>());
    addJump(branchTest32(NonZero, regT0), target);
#endif
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::valueIsTruthyGenerator(VM& vm)
{
    // The thunk generated by this function can only work with the LLInt / Baseline JIT because
    // it makes assumptions about the right globalObject being available from CallFrame::codeBlock().
    // DFG/FTL may inline functions belonging to other globalObjects, which may not match
    // CallFrame::codeBlock().
    CCallHelpers jit;

    constexpr GPRReg value = regT0;
    constexpr GPRReg scratch1 = regT1;
    constexpr GPRReg scratch2 = regT2;
    constexpr bool shouldCheckMasqueradesAsUndefined = true;

    jit.tagReturnAddress();

    constexpr GPRReg globalObjectGPR = regT3;
    jit.loadPtr(addressFor(CallFrameSlot::codeBlock), globalObjectGPR);
    jit.loadPtr(Address(globalObjectGPR, CodeBlock::offsetOfGlobalObject()), globalObjectGPR);
    auto isTruthy = jit.branchIfTruthy(vm, JSValueRegs(value), scratch1, scratch2, fpRegT0, fpRegT1, shouldCheckMasqueradesAsUndefined, globalObjectGPR);
    jit.move(TrustedImm32(0), regT0);
    Jump done = jit.jump();

    isTruthy.link(&jit);
    jit.move(TrustedImm32(1), regT0);

    done.link(&jit);
    jit.ret();

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::Thunk);
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: valueIsfalsey");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

void JIT::emit_op_neq(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNeq>();
    emitGetVirtualRegisters(bytecode.m_lhs, regT0, bytecode.m_rhs, regT1);
    emitJumpSlowCaseIfNotInt(regT0, regT1, regT2);
    compare32(NotEqual, regT1, regT0, regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });

    emitPutVirtualRegister(bytecode.m_dst);
}

void JIT::emit_op_jneq(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpJneq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    emitGetVirtualRegisters(bytecode.m_lhs, regT0, bytecode.m_rhs, regT1);
    emitJumpSlowCaseIfNotInt(regT0, regT1, regT2);
    addJump(branch32(NotEqual, regT0, regT1), target);
}

void JIT::emit_op_throw(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpThrow>();
    ASSERT(regT0 == returnValueGPR);

#if !ENABLE(EXTRA_CTI_THUNKS)
    copyCalleeSavesToEntryFrameCalleeSavesBuffer(vm().topEntryFrame);
    emitGetVirtualRegister(bytecode.m_value, regT0);
    loadGlobalObject(regT1);
    callOperationNoExceptionCheck(operationThrow, regT1, regT0);
    jumpToExceptionHandler(vm());
#else
    constexpr GPRReg bytecodeOffsetGPR = argumentGPR2;
    constexpr GPRReg thrownValueGPR = argumentGPR1;

    uint32_t bytecodeOffset = m_bytecodeIndex.offset();
    move(TrustedImm32(bytecodeOffset), bytecodeOffsetGPR);
    emitGetVirtualRegister(bytecode.m_value, thrownValueGPR);
    emitNakedNearJump(vm().getCTIStub(op_throw_handlerGenerator).code());
#endif // ENABLE(EXTRA_CTI_THUNKS)
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::op_throw_handlerGenerator(VM& vm)
{
    CCallHelpers jit;

    constexpr GPRReg bytecodeOffsetGPR = argumentGPR2;
    constexpr GPRReg thrownValueGPR = argumentGPR1;
    
    jit.store32(bytecodeOffsetGPR, tagFor(CallFrameSlot::argumentCountIncludingThis));

#if NUMBER_OF_CALLEE_SAVES_REGISTERS > 0
    jit.loadPtr(&vm.topEntryFrame, argumentGPR0);
    jit.copyCalleeSavesToEntryFrameCalleeSavesBuffer(argumentGPR0);
#endif

    constexpr GPRReg globalObjectGPR = argumentGPR0;
    jit.loadPtr(addressFor(CallFrameSlot::codeBlock), globalObjectGPR);
    jit.loadPtr(Address(globalObjectGPR, CodeBlock::offsetOfGlobalObject()), globalObjectGPR);

    jit.setupArguments<decltype(operationThrow)>(globalObjectGPR, thrownValueGPR);
    jit.prepareCallOperation(vm);
    Call operation = jit.call(OperationPtrTag);
    jit.jumpToExceptionHandler(vm);

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::ExtraCTIThunk);
    patchBuffer.link(operation, FunctionPtr<OperationPtrTag>(operationThrow));
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: op_throw_handler");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

template<typename Op>
void JIT::compileOpStrictEq(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<Op>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src1 = bytecode.m_lhs;
    VirtualRegister src2 = bytecode.m_rhs;

    emitGetVirtualRegisters(src1, regT0, src2, regT1);

#if USE(BIGINT32)
    /* At a high level we do (assuming 'type' to be StrictEq):
    If (left is Double || right is Double)
        goto slowPath;
    result = (left == right);
    if (result)
        goto done;
    if (left is Cell || right is Cell)
        goto slowPath;
    done:
    return result;
    */

    // This fragment implements (left is Double || right is Double), with a single branch instead of the 4 that would be naively required if we used branchIfInt32/branchIfNumber
    // The trick is that if a JSValue is an Int32, then adding 1<<49 to it will make it overflow, leaving all high bits at 0
    // If it is not a number at all, then 1<<49 will be its only high bit set
    // Leaving only doubles above or equal 1<<50.
    move(regT0, regT2);
    move(regT1, regT3);
    move(TrustedImm64(JSValue::LowestOfHighBits), regT5);
    add64(regT5, regT2);
    add64(regT5, regT3);
    lshift64(TrustedImm32(1), regT5);
    or64(regT2, regT3);
    addSlowCase(branch64(AboveOrEqual, regT3, regT5));

    compare64(Equal, regT0, regT1, regT5);
    Jump done = branchTest64(NonZero, regT5);

    move(regT0, regT2);
    // Jump slow if at least one is a cell (to cover strings and BigInts).
    and64(regT1, regT2);
    // FIXME: we could do something more precise: unless there is a BigInt32, we only need to do the slow path if both are strings
    addSlowCase(branchIfCell(regT2));

    done.link(this);
    if constexpr (std::is_same<Op, OpNstricteq>::value)
        xor64(TrustedImm64(1), regT5);
    boxBoolean(regT5, JSValueRegs { regT5 });
    emitPutVirtualRegister(dst, regT5);
#else // if !USE(BIGINT32)
    // Jump slow if both are cells (to cover strings).
    move(regT0, regT2);
    or64(regT1, regT2);
    addSlowCase(branchIfCell(regT2));

    // Jump slow if either is a double. First test if it's an integer, which is fine, and then test
    // if it's a double.
    Jump leftOK = branchIfInt32(regT0);
    addSlowCase(branchIfNumber(regT0));
    leftOK.link(this);
    Jump rightOK = branchIfInt32(regT1);
    addSlowCase(branchIfNumber(regT1));
    rightOK.link(this);

    if constexpr (std::is_same<Op, OpStricteq>::value)
        compare64(Equal, regT1, regT0, regT0);
    else
        compare64(NotEqual, regT1, regT0, regT0);
    boxBoolean(regT0, JSValueRegs { regT0 });

    emitPutVirtualRegister(dst);
#endif
}

void JIT::emit_op_stricteq(const Instruction* currentInstruction)
{
    compileOpStrictEq<OpStricteq>(currentInstruction);
}

void JIT::emit_op_nstricteq(const Instruction* currentInstruction)
{
    compileOpStrictEq<OpNstricteq>(currentInstruction);
}

template<typename Op>
void JIT::compileOpStrictEqJump(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<Op>();
    int target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    VirtualRegister src1 = bytecode.m_lhs;
    VirtualRegister src2 = bytecode.m_rhs;

    emitGetVirtualRegisters(src1, regT0, src2, regT1);

#if USE(BIGINT32)
    /* At a high level we do (assuming 'type' to be StrictEq):
    If (left is Double || right is Double)
       goto slowPath;
    if (left == right)
       goto taken;
    if (left is Cell || right is Cell)
       goto slowPath;
    goto notTaken;
    */

    // This fragment implements (left is Double || right is Double), with a single branch instead of the 4 that would be naively required if we used branchIfInt32/branchIfNumber
    // The trick is that if a JSValue is an Int32, then adding 1<<49 to it will make it overflow, leaving all high bits at 0
    // If it is not a number at all, then 1<<49 will be its only high bit set
    // Leaving only doubles above or equal 1<<50.
    move(regT0, regT2);
    move(regT1, regT3);
    move(TrustedImm64(JSValue::LowestOfHighBits), regT5);
    add64(regT5, regT2);
    add64(regT5, regT3);
    lshift64(TrustedImm32(1), regT5);
    or64(regT2, regT3);
    addSlowCase(branch64(AboveOrEqual, regT3, regT5));

    Jump areEqual = branch64(Equal, regT0, regT1);
    if constexpr (std::is_same<Op, OpJstricteq>::value)
        addJump(areEqual, target);

    move(regT0, regT2);
    // Jump slow if at least one is a cell (to cover strings and BigInts).
    and64(regT1, regT2);
    // FIXME: we could do something more precise: unless there is a BigInt32, we only need to do the slow path if both are strings
    addSlowCase(branchIfCell(regT2));

    if constexpr (std::is_same<Op, OpJnstricteq>::value) {
        addJump(jump(), target);
        areEqual.link(this);
    }
#else // if !USE(BIGINT32)
    // Jump slow if both are cells (to cover strings).
    move(regT0, regT2);
    or64(regT1, regT2);
    addSlowCase(branchIfCell(regT2));

    // Jump slow if either is a double. First test if it's an integer, which is fine, and then test
    // if it's a double.
    Jump leftOK = branchIfInt32(regT0);
    addSlowCase(branchIfNumber(regT0));
    leftOK.link(this);
    Jump rightOK = branchIfInt32(regT1);
    addSlowCase(branchIfNumber(regT1));
    rightOK.link(this);
    if constexpr (std::is_same<Op, OpJstricteq>::value)
        addJump(branch64(Equal, regT1, regT0), target);
    else
        addJump(branch64(NotEqual, regT1, regT0), target);
#endif
}

void JIT::emit_op_jstricteq(const Instruction* currentInstruction)
{
    compileOpStrictEqJump<OpJstricteq>(currentInstruction);
}

void JIT::emit_op_jnstricteq(const Instruction* currentInstruction)
{
    compileOpStrictEqJump<OpJnstricteq>(currentInstruction);
}

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

    auto bytecode = currentInstruction->as<OpJstricteq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    loadGlobalObject(regT2);
    callOperation(operationCompareStrictEq, regT2, regT0, regT1);
    emitJumpSlowToHot(branchTest32(NonZero, returnValueGPR), target);
}

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

    auto bytecode = currentInstruction->as<OpJnstricteq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    loadGlobalObject(regT2);
    callOperation(operationCompareStrictEq, regT2, regT0, regT1);
    emitJumpSlowToHot(branchTest32(Zero, returnValueGPR), target);
}

void JIT::emit_op_to_number(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToNumber>();
    VirtualRegister dstVReg = bytecode.m_dst;
    VirtualRegister srcVReg = bytecode.m_operand;
    emitGetVirtualRegister(srcVReg, regT0);
    
    addSlowCase(branchIfNotNumber(regT0));

    emitValueProfilingSite(bytecode, regT0);
    if (srcVReg != dstVReg)
        emitPutVirtualRegister(dstVReg);
}

void JIT::emit_op_to_numeric(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToNumeric>();
    VirtualRegister dstVReg = bytecode.m_dst;
    VirtualRegister srcVReg = bytecode.m_operand;
    emitGetVirtualRegister(srcVReg, regT0);

    Jump isNotCell = branchIfNotCell(regT0);
    addSlowCase(branchIfNotHeapBigInt(regT0));
    Jump isBigInt = jump();

    isNotCell.link(this);
    addSlowCase(branchIfNotNumber(regT0));
    isBigInt.link(this);

    emitValueProfilingSite(bytecode, regT0);
    if (srcVReg != dstVReg)
        emitPutVirtualRegister(dstVReg);
}

void JIT::emit_op_to_string(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToString>();
    VirtualRegister srcVReg = bytecode.m_operand;
    emitGetVirtualRegister(srcVReg, regT0);

    addSlowCase(branchIfNotCell(regT0));
    addSlowCase(branchIfNotString(regT0));

    emitPutVirtualRegister(bytecode.m_dst);
}

void JIT::emit_op_to_object(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToObject>();
    VirtualRegister dstVReg = bytecode.m_dst;
    VirtualRegister srcVReg = bytecode.m_operand;
    emitGetVirtualRegister(srcVReg, regT0);

    addSlowCase(branchIfNotCell(regT0));
    addSlowCase(branchIfNotObject(regT0));

    emitValueProfilingSite(bytecode, regT0);
    if (srcVReg != dstVReg)
        emitPutVirtualRegister(dstVReg);
}

void JIT::emit_op_catch(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpCatch>();

    restoreCalleeSavesFromEntryFrameCalleeSavesBuffer(vm().topEntryFrame);

    move(TrustedImmPtr(m_vm), regT3);
    load64(Address(regT3, VM::callFrameForCatchOffset()), callFrameRegister);
    storePtr(TrustedImmPtr(nullptr), Address(regT3, VM::callFrameForCatchOffset()));

    addPtr(TrustedImm32(stackPointerOffsetFor(m_unlinkedCodeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);

    // When the LLInt throws an exception, there is a chance that we've already tiered up
    // the same CodeBlock to baseline, and we'll catch the exception in the baseline JIT (because
    // we updated the exception handlers to point here). Because the LLInt uses a different value
    // inside s_constantsGPR, the callee saves we restore above may not contain the correct register.
    // So we replenish it here.
    {
        loadPtr(addressFor(CallFrameSlot::codeBlock), regT0);
        loadPtr(Address(regT0, CodeBlock::offsetOfJITData()), regT0);
        loadPtr(Address(regT0, CodeBlock::JITData::offsetOfJITConstantPool()), s_constantsGPR);
    }

    callOperationNoExceptionCheck(operationRetrieveAndClearExceptionIfCatchable, &vm());
    Jump isCatchableException = branchTest32(NonZero, returnValueGPR);
    jumpToExceptionHandler(vm());
    isCatchableException.link(this);

    move(returnValueGPR, regT0);
    emitPutVirtualRegister(bytecode.m_exception);

    load64(Address(regT0, Exception::valueOffset()), regT0);
    emitPutVirtualRegister(bytecode.m_thrownValue);

#if ENABLE(DFG_JIT)
    // FIXME: consider inline caching the process of doing OSR entry, including
    // argument type proofs, storing locals to the buffer, etc
    // https://bugs.webkit.org/show_bug.cgi?id=175598

    callOperationNoExceptionCheck(operationTryOSREnterAtCatchAndValueProfile, &vm(), m_bytecodeIndex.asBits());
    auto skipOSREntry = branchTestPtr(Zero, returnValueGPR);
    emitRestoreCalleeSaves();
    farJump(returnValueGPR, ExceptionHandlerPtrTag);
    skipOSREntry.link(this);
#endif // ENABLE(DFG_JIT)
}

void JIT::emit_op_identity_with_profile(const Instruction*)
{
    // We don't need to do anything here...
}

void JIT::emit_op_get_parent_scope(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpGetParentScope>();
    VirtualRegister currentScope = bytecode.m_scope;
    emitGetVirtualRegister(currentScope, regT0);
    loadPtr(Address(regT0, JSScope::offsetOfNext()), regT0);
    emitStoreCell(bytecode.m_dst, regT0);
}

void JIT::emit_op_switch_imm(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpSwitchImm>();
    size_t tableIndex = bytecode.m_tableIndex;
    unsigned defaultOffset = jumpTarget(currentInstruction, bytecode.m_defaultOffset);
    VirtualRegister scrutinee = bytecode.m_scrutinee;

    // create jump table for switch destinations, track this switch statement.
    const UnlinkedSimpleJumpTable& unlinkedTable = m_unlinkedCodeBlock->unlinkedSwitchJumpTable(tableIndex);
    SimpleJumpTable& linkedTable = m_switchJumpTables[tableIndex];
    m_switches.append(SwitchRecord(tableIndex, m_bytecodeIndex, defaultOffset, SwitchRecord::Immediate));
    linkedTable.ensureCTITable(unlinkedTable);

    emitGetVirtualRegister(scrutinee, regT0);
    auto notInt32 = branchIfNotInt32(regT0);
    sub32(Imm32(unlinkedTable.m_min), regT0);

    addJump(branch32(AboveOrEqual, regT0, Imm32(linkedTable.m_ctiOffsets.size())), defaultOffset);
    move(TrustedImmPtr(linkedTable.m_ctiOffsets.data()), regT1);
    farJump(BaseIndex(regT1, regT0, ScalePtr), JSSwitchPtrTag);

    notInt32.link(this);
    callOperationNoExceptionCheck(operationSwitchImmWithUnknownKeyType, &vm(), regT0, tableIndex, unlinkedTable.m_min);
    farJump(returnValueGPR, JSSwitchPtrTag);
}

void JIT::emit_op_switch_char(const Instruction* currentInstruction)
{
    // FIXME: We should have a fast path.
    // https://bugs.webkit.org/show_bug.cgi?id=224521
    auto bytecode = currentInstruction->as<OpSwitchChar>();
    size_t tableIndex = bytecode.m_tableIndex;
    unsigned defaultOffset = jumpTarget(currentInstruction, bytecode.m_defaultOffset);
    VirtualRegister scrutinee = bytecode.m_scrutinee;

    // create jump table for switch destinations, track this switch statement.
    const UnlinkedSimpleJumpTable& unlinkedTable = m_unlinkedCodeBlock->unlinkedSwitchJumpTable(tableIndex);
    SimpleJumpTable& linkedTable = m_switchJumpTables[tableIndex];
    m_switches.append(SwitchRecord(tableIndex, m_bytecodeIndex, defaultOffset, SwitchRecord::Character));
    linkedTable.ensureCTITable(unlinkedTable);

    emitGetVirtualRegister(scrutinee, argumentGPR1);
    loadGlobalObject(argumentGPR0);
    callOperation(operationSwitchCharWithUnknownKeyType, argumentGPR0, argumentGPR1, tableIndex, unlinkedTable.m_min);
    farJump(returnValueGPR, JSSwitchPtrTag);
}

void JIT::emit_op_switch_string(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpSwitchString>();
    size_t tableIndex = bytecode.m_tableIndex;
    unsigned defaultOffset = jumpTarget(currentInstruction, bytecode.m_defaultOffset);
    VirtualRegister scrutinee = bytecode.m_scrutinee;

    // create jump table for switch destinations, track this switch statement.
    const UnlinkedStringJumpTable& unlinkedTable = m_unlinkedCodeBlock->unlinkedStringSwitchJumpTable(tableIndex);
    StringJumpTable& linkedTable = m_stringSwitchJumpTables[tableIndex];
    m_switches.append(SwitchRecord(tableIndex, m_bytecodeIndex, defaultOffset, SwitchRecord::String));
    linkedTable.ensureCTITable(unlinkedTable);

    emitGetVirtualRegister(scrutinee, argumentGPR1);
    loadGlobalObject(argumentGPR0);
    callOperation(operationSwitchStringWithUnknownKeyType, argumentGPR0, argumentGPR1, tableIndex);
    farJump(returnValueGPR, JSSwitchPtrTag);
}

void JIT::emit_op_eq_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpEqNull>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src1 = bytecode.m_operand;

    emitGetVirtualRegister(src1, regT0);
    Jump isImmediate = branchIfNotCell(regT0);

    Jump isMasqueradesAsUndefined = branchTest8(NonZero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(MasqueradesAsUndefined));
    move(TrustedImm32(0), regT0);
    Jump wasNotMasqueradesAsUndefined = jump();

    isMasqueradesAsUndefined.link(this);
    emitLoadStructure(vm(), regT0, regT2, regT1);
    loadGlobalObject(regT0);
    loadPtr(Address(regT2, Structure::globalObjectOffset()), regT2);
    comparePtr(Equal, regT0, regT2, regT0);
    Jump wasNotImmediate = jump();

    isImmediate.link(this);

    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    compare64(Equal, regT0, TrustedImm32(JSValue::ValueNull), regT0);

    wasNotImmediate.link(this);
    wasNotMasqueradesAsUndefined.link(this);

    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_neq_null(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNeqNull>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister src1 = bytecode.m_operand;

    emitGetVirtualRegister(src1, regT0);
    Jump isImmediate = branchIfNotCell(regT0);

    Jump isMasqueradesAsUndefined = branchTest8(NonZero, Address(regT0, JSCell::typeInfoFlagsOffset()), TrustedImm32(MasqueradesAsUndefined));
    move(TrustedImm32(1), regT0);
    Jump wasNotMasqueradesAsUndefined = jump();

    isMasqueradesAsUndefined.link(this);
    emitLoadStructure(vm(), regT0, regT2, regT1);
    loadGlobalObject(regT0);
    loadPtr(Address(regT2, Structure::globalObjectOffset()), regT2);
    comparePtr(NotEqual, regT0, regT2, regT0);
    Jump wasNotImmediate = jump();

    isImmediate.link(this);

    and64(TrustedImm32(~JSValue::UndefinedTag), regT0);
    compare64(NotEqual, regT0, TrustedImm32(JSValue::ValueNull), regT0);

    wasNotImmediate.link(this);
    wasNotMasqueradesAsUndefined.link(this);

    boxBoolean(regT0, JSValueRegs { regT0 });
    emitPutVirtualRegister(dst);
}

void JIT::emit_op_enter(const Instruction*)
{
    // Even though CTI doesn't use them, we initialize our constant
    // registers to zap stale pointers, to avoid unnecessarily prolonging
    // object lifetime and increasing GC pressure.
    size_t count = m_unlinkedCodeBlock->numVars();
#if !ENABLE(EXTRA_CTI_THUNKS)
    for (size_t j = CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters(); j < count; ++j)
        emitInitRegister(virtualRegisterForLocal(j));

    
    loadPtr(addressFor(CallFrameSlot::codeBlock), regT0);
    emitWriteBarrier(regT0);

    emitEnterOptimizationCheck();
#else
    ASSERT(m_bytecodeIndex.offset() == 0);
    constexpr GPRReg localsToInitGPR = argumentGPR0;
    constexpr GPRReg canBeOptimizedGPR = argumentGPR4;

    unsigned localsToInit = count - CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters();
    RELEASE_ASSERT(localsToInit < count);
    move(TrustedImm32(localsToInit * sizeof(Register)), localsToInitGPR);
    move(TrustedImm32(canBeOptimized()), canBeOptimizedGPR);
    emitNakedNearCall(vm().getCTIStub(op_enter_handlerGenerator).retaggedCode<NoPtrTag>());
#endif // ENABLE(EXTRA_CTI_THUNKS)
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::op_enter_handlerGenerator(VM& vm)
{
    CCallHelpers jit;

#if CPU(X86_64)
    jit.push(X86Registers::ebp);
#elif CPU(ARM64)
    jit.tagReturnAddress();
    jit.pushPair(framePointerRegister, linkRegister);
#endif
    // op_enter is always at bytecodeOffset 0.
    jit.store32(TrustedImm32(0), tagFor(CallFrameSlot::argumentCountIncludingThis));

    constexpr GPRReg localsToInitGPR = argumentGPR0;
    constexpr GPRReg iteratorGPR = argumentGPR1;
    constexpr GPRReg endGPR = argumentGPR2;
    constexpr GPRReg undefinedGPR = argumentGPR3;
    constexpr GPRReg canBeOptimizedGPR = argumentGPR4;

    size_t startLocal = CodeBlock::llintBaselineCalleeSaveSpaceAsVirtualRegisters();
    int startOffset = virtualRegisterForLocal(startLocal).offset();
    jit.move(TrustedImm64(startOffset * sizeof(Register)), iteratorGPR);
    jit.sub64(iteratorGPR, localsToInitGPR, endGPR);

    jit.move(TrustedImm64(JSValue::encode(jsUndefined())), undefinedGPR);
    auto initLoop = jit.label();
    Jump initDone = jit.branch32(LessThanOrEqual, iteratorGPR, endGPR);
    {
        jit.store64(undefinedGPR, BaseIndex(GPRInfo::callFrameRegister, iteratorGPR, TimesOne));
        jit.sub64(TrustedImm32(sizeof(Register)), iteratorGPR);
        jit.jump(initLoop);
    }
    initDone.link(&jit);

    // emitWriteBarrier(m_codeBlock).
    jit.loadPtr(addressFor(CallFrameSlot::codeBlock), argumentGPR1);
    Jump ownerIsRememberedOrInEden = jit.barrierBranch(vm, argumentGPR1, argumentGPR2);

    jit.move(canBeOptimizedGPR, GPRInfo::numberTagRegister); // save.
    jit.setupArguments<decltype(operationWriteBarrierSlowPath)>(&vm, argumentGPR1);
    jit.prepareCallOperation(vm);
    Call operationWriteBarrierCall = jit.call(OperationPtrTag);

    jit.move(GPRInfo::numberTagRegister, canBeOptimizedGPR); // restore.
    jit.move(TrustedImm64(JSValue::NumberTag), GPRInfo::numberTagRegister);
    ownerIsRememberedOrInEden.link(&jit);

#if ENABLE(DFG_JIT)
    Call operationOptimizeCall;
    if (Options::useDFGJIT()) {
        // emitEnterOptimizationCheck().
        JumpList skipOptimize;

        skipOptimize.append(jit.branchTest32(Zero, canBeOptimizedGPR));

        jit.loadPtr(addressFor(CallFrameSlot::codeBlock), argumentGPR1);
        skipOptimize.append(jit.branchAdd32(Signed, TrustedImm32(Options::executionCounterIncrementForEntry()), Address(argumentGPR1, CodeBlock::offsetOfJITExecuteCounter())));

        jit.copyLLIntBaselineCalleeSavesFromFrameOrRegisterToEntryFrameCalleeSavesBuffer(vm.topEntryFrame);

        jit.setupArguments<decltype(operationOptimize)>(&vm, TrustedImm32(0));
        jit.prepareCallOperation(vm);
        operationOptimizeCall = jit.call(OperationPtrTag);

        skipOptimize.append(jit.branchTestPtr(Zero, returnValueGPR));
        jit.farJump(returnValueGPR, GPRInfo::callFrameRegister);

        skipOptimize.link(&jit);
    }
#endif // ENABLE(DFG_JIT)

#if CPU(X86_64)
    jit.pop(X86Registers::ebp);
#elif CPU(ARM64)
    jit.popPair(framePointerRegister, linkRegister);
#endif
    jit.ret();

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::ExtraCTIThunk);
    patchBuffer.link(operationWriteBarrierCall, FunctionPtr<OperationPtrTag>(operationWriteBarrierSlowPath));
#if ENABLE(DFG_JIT)
    if (Options::useDFGJIT())
        patchBuffer.link(operationOptimizeCall, FunctionPtr<OperationPtrTag>(operationOptimize));
#endif
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: op_enter_handler");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

void JIT::emit_op_get_scope(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpGetScope>();
    VirtualRegister dst = bytecode.m_dst;
    emitGetFromCallFrameHeaderPtr(CallFrameSlot::callee, regT0);
    loadPtr(Address(regT0, JSFunction::offsetOfScopeChain()), regT0);
    emitStoreCell(dst, regT0);
}

void JIT::emit_op_to_this(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpToThis>();
    emitGetVirtualRegister(bytecode.m_srcDst, regT1);

    emitJumpSlowCaseIfNotJSCell(regT1);

    addSlowCase(branchIfNotType(regT1, FinalObjectType));
    load32FromMetadata(bytecode, OpToThis::Metadata::offsetOfCachedStructureID(), regT2);
    addSlowCase(branch32(NotEqual, Address(regT1, JSCell::structureIDOffset()), regT2));
}

void JIT::emit_op_create_this(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpCreateThis>();
    VirtualRegister callee = bytecode.m_callee;
    RegisterID calleeReg = regT0;
    RegisterID rareDataReg = regT4;
    RegisterID resultReg = regT0;
    RegisterID allocatorReg = regT1;
    RegisterID structureReg = regT2;
    RegisterID cachedFunctionReg = regT4;
    RegisterID scratchReg = regT3;

    emitGetVirtualRegister(callee, calleeReg);
    addSlowCase(branchIfNotFunction(calleeReg));
    loadPtr(Address(calleeReg, JSFunction::offsetOfExecutableOrRareData()), rareDataReg);
    addSlowCase(branchTestPtr(Zero, rareDataReg, TrustedImm32(JSFunction::rareDataTag)));
    loadPtr(Address(rareDataReg, FunctionRareData::offsetOfObjectAllocationProfile() + ObjectAllocationProfileWithPrototype::offsetOfAllocator() - JSFunction::rareDataTag), allocatorReg);
    loadPtr(Address(rareDataReg, FunctionRareData::offsetOfObjectAllocationProfile() + ObjectAllocationProfileWithPrototype::offsetOfStructure() - JSFunction::rareDataTag), structureReg);

    loadPtrFromMetadata(bytecode, OpCreateThis::Metadata::offsetOfCachedCallee(), cachedFunctionReg);
    Jump hasSeenMultipleCallees = branchPtr(Equal, cachedFunctionReg, TrustedImmPtr(JSCell::seenMultipleCalleeObjects()));
    addSlowCase(branchPtr(NotEqual, calleeReg, cachedFunctionReg));
    hasSeenMultipleCallees.link(this);

    JumpList slowCases;
    auto butterfly = TrustedImmPtr(nullptr);
    emitAllocateJSObject(resultReg, JITAllocator::variable(), allocatorReg, structureReg, butterfly, scratchReg, slowCases);
    load8(Address(structureReg, Structure::inlineCapacityOffset()), scratchReg);
    emitInitializeInlineStorage(resultReg, scratchReg);
    mutatorFence(*m_vm);
    addSlowCase(slowCases);
    emitPutVirtualRegister(bytecode.m_dst);
}

void JIT::emit_op_check_tdz(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpCheckTdz>();
    emitGetVirtualRegister(bytecode.m_targetVirtualRegister, regT0);
    addSlowCase(branchIfEmpty(regT0));
}


// Slow cases

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

    auto bytecode = currentInstruction->as<OpEq>();
    loadGlobalObject(regT2);
    callOperation(operationCompareEq, regT2, regT0, regT1);
    boxBoolean(returnValueGPR, JSValueRegs { returnValueGPR });
    emitPutVirtualRegister(bytecode.m_dst, returnValueGPR);
}

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

    auto bytecode = currentInstruction->as<OpNeq>();
    loadGlobalObject(regT2);
    callOperation(operationCompareEq, regT2, regT0, regT1);
    xor32(TrustedImm32(0x1), regT0);
    boxBoolean(returnValueGPR, JSValueRegs { returnValueGPR });
    emitPutVirtualRegister(bytecode.m_dst, returnValueGPR);
}

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

    auto bytecode = currentInstruction->as<OpJeq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    loadGlobalObject(regT2);
    callOperation(operationCompareEq, regT2, regT0, regT1);
    emitJumpSlowToHot(branchTest32(NonZero, returnValueGPR), target);
}

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

    auto bytecode = currentInstruction->as<OpJneq>();
    unsigned target = jumpTarget(currentInstruction, bytecode.m_targetLabel);
    loadGlobalObject(regT2);
    callOperation(operationCompareEq, regT2, regT0, regT1);
    emitJumpSlowToHot(branchTest32(Zero, returnValueGPR), target);
}

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

    auto bytecode = currentInstruction->as<OpInstanceofCustom>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister value = bytecode.m_value;
    VirtualRegister constructor = bytecode.m_constructor;
    VirtualRegister hasInstanceValue = bytecode.m_hasInstanceValue;

    emitGetVirtualRegister(value, GPRInfo::argumentGPR1);
    emitGetVirtualRegister(constructor, GPRInfo::argumentGPR2);
    emitGetVirtualRegister(hasInstanceValue, GPRInfo::argumentGPR3);
    loadGlobalObject(GPRInfo::argumentGPR0);
    callOperation(operationInstanceOfCustom, GPRInfo::argumentGPR0, GPRInfo::argumentGPR1, GPRInfo::argumentGPR2, GPRInfo::argumentGPR3);
    boxBoolean(returnValueGPR, JSValueRegs { returnValueGPR });
    emitPutVirtualRegister(dst, returnValueGPR);
}

#endif // USE(JSVALUE64)

void JIT::emit_op_debug(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpDebug>();
    loadPtr(addressFor(CallFrameSlot::codeBlock), regT0);
    load32(Address(regT0, CodeBlock::offsetOfDebuggerRequests()), regT0);
    Jump noDebuggerRequests = branchTest32(Zero, regT0);
    callOperation(operationDebug, &vm(), static_cast<int>(bytecode.m_debugHookType));
    noDebuggerRequests.link(this);
}

void JIT::emit_op_loop_hint(const Instruction* instruction)
{
    if (UNLIKELY(Options::returnEarlyFromInfiniteLoopsForFuzzing() && m_unlinkedCodeBlock->loopHintsAreEligibleForFuzzingEarlyReturn())) {
        uintptr_t* ptr = vm().getLoopHintExecutionCounter(instruction);
        loadPtr(ptr, regT0);
        auto skipEarlyReturn = branchPtr(Below, regT0, TrustedImmPtr(Options::earlyReturnFromInfiniteLoopsLimit()));

#if USE(JSVALUE64)
        JSValueRegs resultRegs(GPRInfo::returnValueGPR);
        loadGlobalObject(resultRegs.gpr());
#else
        JSValueRegs resultRegs(GPRInfo::returnValueGPR2, GPRInfo::returnValueGPR);
        loadGlobalObject(resultRegs.payloadGPR());
        move(TrustedImm32(JSValue::CellTag), resultRegs.tagGPR());
#endif
        checkStackPointerAlignment();
        emitRestoreCalleeSaves();
        emitFunctionEpilogue();
        ret();

        skipEarlyReturn.link(this);
        addPtr(TrustedImm32(1), regT0);
        storePtr(regT0, ptr);
    }

    // Emit the JIT optimization check: 
    if (canBeOptimized()) {
        loadPtr(addressFor(CallFrameSlot::codeBlock), regT0);
        addSlowCase(branchAdd32(PositiveOrZero, TrustedImm32(Options::executionCounterIncrementForLoop()),
            Address(regT0, CodeBlock::offsetOfJITExecuteCounter())));
    }
}

void JIT::emitSlow_op_loop_hint(const Instruction* currentInstruction, Vector<SlowCaseEntry>::iterator& iter)
{
#if ENABLE(DFG_JIT)
    // Emit the slow path for the JIT optimization check:
    if (canBeOptimized()) {
        linkAllSlowCases(iter);

        copyLLIntBaselineCalleeSavesFromFrameOrRegisterToEntryFrameCalleeSavesBuffer(vm().topEntryFrame);

        callOperationNoExceptionCheck(operationOptimize, &vm(), m_bytecodeIndex.asBits());
        Jump noOptimizedEntry = branchTestPtr(Zero, returnValueGPR);
        if (ASSERT_ENABLED) {
            Jump ok = branchPtr(MacroAssembler::Above, returnValueGPR, TrustedImmPtr(bitwise_cast<void*>(static_cast<intptr_t>(1000))));
            abortWithReason(JITUnreasonableLoopHintJumpTarget);
            ok.link(this);
        }
        farJump(returnValueGPR, GPRInfo::callFrameRegister);
        noOptimizedEntry.link(this);

        emitJumpSlowToHot(jump(), currentInstruction->size());
    }
#else
    UNUSED_PARAM(currentInstruction);
    UNUSED_PARAM(iter);
#endif
}

void JIT::emit_op_check_traps(const Instruction*)
{
    addSlowCase(branchTest32(NonZero, AbsoluteAddress(m_vm->traps().trapBitsAddress()), TrustedImm32(VMTraps::AsyncEvents)));
}

void JIT::emit_op_nop(const Instruction*)
{
}

void JIT::emit_op_super_sampler_begin(const Instruction*)
{
    add32(TrustedImm32(1), AbsoluteAddress(bitwise_cast<void*>(&g_superSamplerCount)));
}

void JIT::emit_op_super_sampler_end(const Instruction*)
{
    sub32(TrustedImm32(1), AbsoluteAddress(bitwise_cast<void*>(&g_superSamplerCount)));
}

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

#if !ENABLE(EXTRA_CTI_THUNKS)
    loadGlobalObject(argumentGPR0);
    callOperation(operationHandleTraps, argumentGPR0);
#else
    constexpr GPRReg bytecodeOffsetGPR = argumentGPR3;
    uint32_t bytecodeOffset = m_bytecodeIndex.offset();
    move(TrustedImm32(bytecodeOffset), bytecodeOffsetGPR);

    emitNakedNearCall(vm().getCTIStub(op_check_traps_handlerGenerator).retaggedCode<NoPtrTag>());
#endif
}

#if ENABLE(EXTRA_CTI_THUNKS)
MacroAssemblerCodeRef<JITThunkPtrTag> JIT::op_check_traps_handlerGenerator(VM& vm)
{
    CCallHelpers jit;

#if CPU(X86_64)
    jit.push(X86Registers::ebp);
#elif CPU(ARM64)
    jit.tagReturnAddress();
    jit.pushPair(framePointerRegister, linkRegister);
#endif

    constexpr GPRReg bytecodeOffsetGPR = argumentGPR3;
    jit.store32(bytecodeOffsetGPR, tagFor(CallFrameSlot::argumentCountIncludingThis));

    constexpr GPRReg codeBlockGPR = argumentGPR3;
    constexpr GPRReg globalObjectGPR = argumentGPR0;
    jit.loadPtr(addressFor(CallFrameSlot::codeBlock), codeBlockGPR);
    jit.loadPtr(Address(codeBlockGPR, CodeBlock::offsetOfGlobalObject()), globalObjectGPR);
    
    jit.setupArguments<decltype(operationHandleTraps)>(globalObjectGPR);
    jit.prepareCallOperation(vm);
    CCallHelpers::Call operation = jit.call(OperationPtrTag);
    CCallHelpers::Jump exceptionCheck = jit.emitNonPatchableExceptionCheck(vm);

#if CPU(X86_64)
    jit.pop(X86Registers::ebp);
#elif CPU(ARM64)
    jit.popPair(framePointerRegister, linkRegister);
#endif
    jit.ret();

    LinkBuffer patchBuffer(jit, GLOBAL_THUNK_ID, LinkBuffer::Profile::ExtraCTIThunk);
    patchBuffer.link(operation, FunctionPtr<OperationPtrTag>(operationHandleTraps));
    auto handler = vm.getCTIStub(popThunkStackPreservesAndHandleExceptionGenerator);
    patchBuffer.link(exceptionCheck, CodeLocationLabel(handler.retaggedCode<NoPtrTag>()));
    return FINALIZE_CODE(patchBuffer, JITThunkPtrTag, "Baseline: op_check_traps_handler");
}
#endif // ENABLE(EXTRA_CTI_THUNKS)

void JIT::emit_op_new_regexp(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNewRegexp>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister regexp = bytecode.m_regexp;
    GPRReg globalGPR = argumentGPR0;
    loadGlobalObject(globalGPR);
    callOperation(operationNewRegexp, globalGPR, jsCast<RegExp*>(m_unlinkedCodeBlock->getConstant(regexp)));
    emitStoreCell(dst, returnValueGPR);
}

template<typename Op>
void JIT::emitNewFuncCommon(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<Op>();
    VirtualRegister dst = bytecode.m_dst;

#if USE(JSVALUE64)
    emitGetVirtualRegister(bytecode.m_scope, argumentGPR1);
#else
    emitLoadPayload(bytecode.m_scope, argumentGPR1);
#endif
    auto constant = addToConstantPool(JITConstantPool::Type::FunctionDecl, bitwise_cast<void*>(static_cast<uintptr_t>(bytecode.m_functionDecl)));
    loadConstant(constant, argumentGPR2);

    OpcodeID opcodeID = Op::opcodeID;
    if (opcodeID == op_new_func)
        callOperation(operationNewFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else if (opcodeID == op_new_generator_func)
        callOperation(operationNewGeneratorFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else if (opcodeID == op_new_async_func)
        callOperation(operationNewAsyncFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else {
        ASSERT(opcodeID == op_new_async_generator_func);
        callOperation(operationNewAsyncGeneratorFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    }
}

void JIT::emit_op_new_func(const Instruction* currentInstruction)
{
    emitNewFuncCommon<OpNewFunc>(currentInstruction);
}

void JIT::emit_op_new_generator_func(const Instruction* currentInstruction)
{
    emitNewFuncCommon<OpNewGeneratorFunc>(currentInstruction);
}

void JIT::emit_op_new_async_generator_func(const Instruction* currentInstruction)
{
    emitNewFuncCommon<OpNewAsyncGeneratorFunc>(currentInstruction);
}

void JIT::emit_op_new_async_func(const Instruction* currentInstruction)
{
    emitNewFuncCommon<OpNewAsyncFunc>(currentInstruction);
}
    
template<typename Op>
void JIT::emitNewFuncExprCommon(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<Op>();
    VirtualRegister dst = bytecode.m_dst;
#if USE(JSVALUE64)
    emitGetVirtualRegister(bytecode.m_scope, argumentGPR1);
#else
    emitLoadPayload(bytecode.m_scope, argumentGPR1);
#endif

    auto constant = addToConstantPool(JITConstantPool::Type::FunctionExpr, bitwise_cast<void*>(static_cast<uintptr_t>(bytecode.m_functionDecl)));
    loadConstant(constant, argumentGPR2);
    OpcodeID opcodeID = Op::opcodeID;

    if (opcodeID == op_new_func_exp)
        callOperation(operationNewFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else if (opcodeID == op_new_generator_func_exp)
        callOperation(operationNewGeneratorFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else if (opcodeID == op_new_async_func_exp)
        callOperation(operationNewAsyncFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    else {
        ASSERT(opcodeID == op_new_async_generator_func_exp);
        callOperation(operationNewAsyncGeneratorFunction, dst, &vm(), argumentGPR1, argumentGPR2);
    }
}

void JIT::emit_op_new_func_exp(const Instruction* currentInstruction)
{
    emitNewFuncExprCommon<OpNewFuncExp>(currentInstruction);
}

void JIT::emit_op_new_generator_func_exp(const Instruction* currentInstruction)
{
    emitNewFuncExprCommon<OpNewGeneratorFuncExp>(currentInstruction);
}

void JIT::emit_op_new_async_func_exp(const Instruction* currentInstruction)
{
    emitNewFuncExprCommon<OpNewAsyncFuncExp>(currentInstruction);
}
    
void JIT::emit_op_new_async_generator_func_exp(const Instruction* currentInstruction)
{
    emitNewFuncExprCommon<OpNewAsyncGeneratorFuncExp>(currentInstruction);
}
    
void JIT::emit_op_new_array(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNewArray>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister valuesStart = bytecode.m_argv;
    int size = bytecode.m_argc;
    addPtr(TrustedImm32(valuesStart.offset() * sizeof(Register)), callFrameRegister, argumentGPR2);
    materializePointerIntoMetadata(bytecode, OpNewArray::Metadata::offsetOfArrayAllocationProfile(), argumentGPR1);
    loadGlobalObject(argumentGPR0);
    callOperation(operationNewArrayWithProfile, dst, argumentGPR0, argumentGPR1, argumentGPR2, size);
}

void JIT::emit_op_new_array_with_size(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpNewArrayWithSize>();
    VirtualRegister dst = bytecode.m_dst;
    VirtualRegister sizeIndex = bytecode.m_length;
#if USE(JSVALUE64)
    materializePointerIntoMetadata(bytecode, OpNewArrayWithSize::Metadata::offsetOfArrayAllocationProfile(), argumentGPR1);
    emitGetVirtualRegister(sizeIndex, argumentGPR2);
    loadGlobalObject(argumentGPR0);
    callOperation(operationNewArrayWithSizeAndProfile, dst, argumentGPR0, argumentGPR1, argumentGPR2);
#else
    materializePointerIntoMetadata(bytecode, OpNewArrayWithSize::Metadata::offsetOfArrayAllocationProfile(), regT2);
    emitLoad(sizeIndex, regT1, regT0);
    loadGlobalObject(regT3);
    callOperation(operationNewArrayWithSizeAndProfile, dst, regT3, regT2, JSValueRegs(regT1, regT0));
#endif
}

#if USE(JSVALUE64)

void JIT::emit_op_profile_type(const Instruction* currentInstruction)
{
    m_isShareable = false;

    auto bytecode = currentInstruction->as<OpProfileType>();
    auto& metadata = bytecode.metadata(m_profiledCodeBlock);
    TypeLocation* cachedTypeLocation = metadata.m_typeLocation;
    VirtualRegister valueToProfile = bytecode.m_targetVirtualRegister;

    emitGetVirtualRegister(valueToProfile, regT0);

    JumpList jumpToEnd;

    jumpToEnd.append(branchIfEmpty(regT0));

    // Compile in a predictive type check, if possible, to see if we can skip writing to the log.
    // These typechecks are inlined to match those of the 64-bit JSValue type checks.
    if (cachedTypeLocation->m_lastSeenType == TypeUndefined)
        jumpToEnd.append(branchIfUndefined(regT0));
    else if (cachedTypeLocation->m_lastSeenType == TypeNull)
        jumpToEnd.append(branchIfNull(regT0));
    else if (cachedTypeLocation->m_lastSeenType == TypeBoolean)
        jumpToEnd.append(branchIfBoolean(regT0, regT1));
    else if (cachedTypeLocation->m_lastSeenType == TypeAnyInt)
        jumpToEnd.append(branchIfInt32(regT0));
    else if (cachedTypeLocation->m_lastSeenType == TypeNumber)
        jumpToEnd.append(branchIfNumber(regT0));
    else if (cachedTypeLocation->m_lastSeenType == TypeString) {
        Jump isNotCell = branchIfNotCell(regT0);
        jumpToEnd.append(branchIfString(regT0));
        isNotCell.link(this);
    }

    // Load the type profiling log into T2.
    TypeProfilerLog* cachedTypeProfilerLog = m_vm->typeProfilerLog();
    move(TrustedImmPtr(cachedTypeProfilerLog), regT2);
    // Load the next log entry into T1.
    loadPtr(Address(regT2, TypeProfilerLog::currentLogEntryOffset()), regT1);

    // Store the JSValue onto the log entry.
    store64(regT0, Address(regT1, TypeProfilerLog::LogEntry::valueOffset()));

    // Store the structureID of the cell if T0 is a cell, otherwise, store 0 on the log entry.
    Jump notCell = branchIfNotCell(regT0);
    load32(Address(regT0, JSCell::structureIDOffset()), regT0);
    store32(regT0, Address(regT1, TypeProfilerLog::LogEntry::structureIDOffset()));
    Jump skipIsCell = jump();
    notCell.link(this);
    store32(TrustedImm32(0), Address(regT1, TypeProfilerLog::LogEntry::structureIDOffset()));
    skipIsCell.link(this);

    // Store the typeLocation on the log entry.
    move(TrustedImmPtr(cachedTypeLocation), regT0);
    store64(regT0, Address(regT1, TypeProfilerLog::LogEntry::locationOffset()));

    // Increment the current log entry.
    addPtr(TrustedImm32(sizeof(TypeProfilerLog::LogEntry)), regT1);
    store64(regT1, Address(regT2, TypeProfilerLog::currentLogEntryOffset()));
    Jump skipClearLog = branchPtr(NotEqual, regT1, TrustedImmPtr(cachedTypeProfilerLog->logEndPtr()));
    // Clear the log if we're at the end of the log.
    callOperationNoExceptionCheck(operationProcessTypeProfilerLog, &vm());
    skipClearLog.link(this);

    jumpToEnd.link(this);
}

void JIT::emit_op_log_shadow_chicken_prologue(const Instruction* currentInstruction)
{
    RELEASE_ASSERT(vm().shadowChicken());
    updateTopCallFrame();
    static_assert(nonArgGPR0 != regT0 && nonArgGPR0 != regT2, "we will have problems if this is true.");
    auto bytecode = currentInstruction->as<OpLogShadowChickenPrologue>();
    GPRReg shadowPacketReg = regT0;
    GPRReg scratch1Reg = nonArgGPR0; // This must be a non-argument register.
    GPRReg scratch2Reg = regT2;
    ensureShadowChickenPacket(vm(), shadowPacketReg, scratch1Reg, scratch2Reg);
    emitGetVirtualRegister(bytecode.m_scope, regT3);
    logShadowChickenProloguePacket(shadowPacketReg, scratch1Reg, regT3);
}

void JIT::emit_op_log_shadow_chicken_tail(const Instruction* currentInstruction)
{
    RELEASE_ASSERT(vm().shadowChicken());
    updateTopCallFrame();
    static_assert(nonArgGPR0 != regT0 && nonArgGPR0 != regT2, "we will have problems if this is true.");
    auto bytecode = currentInstruction->as<OpLogShadowChickenTail>();
    GPRReg shadowPacketReg = regT0;
    {
        GPRReg scratch1Reg = nonArgGPR0; // This must be a non-argument register.
        GPRReg scratch2Reg = regT2;
        ensureShadowChickenPacket(vm(), shadowPacketReg, scratch1Reg, scratch2Reg);
    }
    emitGetVirtualRegister(bytecode.m_thisValue, regT2);
    emitGetVirtualRegister(bytecode.m_scope, regT3);
    loadPtr(addressFor(CallFrameSlot::codeBlock), regT1);
    logShadowChickenTailPacket(shadowPacketReg, JSValueRegs(regT2), regT3, regT1, CallSiteIndex(m_bytecodeIndex));
}

#endif // USE(JSVALUE64)

void JIT::emit_op_profile_control_flow(const Instruction* currentInstruction)
{
    m_isShareable = false;

    auto bytecode = currentInstruction->as<OpProfileControlFlow>();
    auto& metadata = bytecode.metadata(m_profiledCodeBlock);
    BasicBlockLocation* basicBlockLocation = metadata.m_basicBlockLocation;
#if USE(JSVALUE64)
    basicBlockLocation->emitExecuteCode(*this);
#else
    basicBlockLocation->emitExecuteCode(*this, regT0);
#endif
}

void JIT::emit_op_argument_count(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpArgumentCount>();
    VirtualRegister dst = bytecode.m_dst;
    load32(payloadFor(CallFrameSlot::argumentCountIncludingThis), regT0);
    sub32(TrustedImm32(1), regT0);
    JSValueRegs result = JSValueRegs::withTwoAvailableRegs(regT0, regT1);
    boxInt32(regT0, result);
    emitPutVirtualRegister(dst, result);
}

void JIT::emit_op_get_rest_length(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpGetRestLength>();
    VirtualRegister dst = bytecode.m_dst;
    unsigned numParamsToSkip = bytecode.m_numParametersToSkip;
    load32(payloadFor(CallFrameSlot::argumentCountIncludingThis), regT0);
    sub32(TrustedImm32(1), regT0);
    Jump zeroLength = branch32(LessThanOrEqual, regT0, Imm32(numParamsToSkip));
    sub32(Imm32(numParamsToSkip), regT0);
#if USE(JSVALUE64)
    boxInt32(regT0, JSValueRegs(regT0));
#endif
    Jump done = jump();

    zeroLength.link(this);
#if USE(JSVALUE64)
    move(TrustedImm64(JSValue::encode(jsNumber(0))), regT0);
#else
    move(TrustedImm32(0), regT0);
#endif

    done.link(this);
#if USE(JSVALUE64)
    emitPutVirtualRegister(dst, regT0);
#else
    move(TrustedImm32(JSValue::Int32Tag), regT1);
    emitPutVirtualRegister(dst, JSValueRegs(regT1, regT0));
#endif
}

void JIT::emit_op_get_argument(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpGetArgument>();
    VirtualRegister dst = bytecode.m_dst;
    int index = bytecode.m_index;
#if USE(JSVALUE64)
    JSValueRegs resultRegs(regT0);
#else
    JSValueRegs resultRegs(regT1, regT0);
#endif

    load32(payloadFor(CallFrameSlot::argumentCountIncludingThis), regT2);
    Jump argumentOutOfBounds = branch32(LessThanOrEqual, regT2, TrustedImm32(index));
    loadValue(addressFor(VirtualRegister(CallFrameSlot::thisArgument + index)), resultRegs);
    Jump done = jump();

    argumentOutOfBounds.link(this);
    moveValue(jsUndefined(), resultRegs);

    done.link(this);
    emitValueProfilingSite(bytecode, resultRegs);
    emitPutVirtualRegister(dst, resultRegs);
}

void JIT::emit_op_get_prototype_of(const Instruction* currentInstruction)
{
    auto bytecode = currentInstruction->as<OpGetPrototypeOf>();
#if USE(JSVALUE64)
    JSValueRegs valueRegs(regT0);
    JSValueRegs resultRegs(regT2);
    GPRReg scratchGPR = regT3;
#else
    JSValueRegs valueRegs(regT1, regT0);
    JSValueRegs resultRegs(regT3, regT2);
    GPRReg scratchGPR = regT1;
    ASSERT(valueRegs.tagGPR() == scratchGPR);
#endif
    emitGetVirtualRegister(bytecode.m_value, valueRegs);

    JumpList slowCases;
    slowCases.append(branchIfNotCell(valueRegs));
    slowCases.append(branchIfNotObject(valueRegs.payloadGPR()));

    emitLoadPrototype(vm(), valueRegs.payloadGPR(), resultRegs, scratchGPR, slowCases);
    addSlowCase(slowCases);

    emitValueProfilingSite(bytecode, resultRegs);
    emitPutVirtualRegister(bytecode.m_dst, resultRegs);
}

} // namespace JSC

#endif // ENABLE(JIT)