path: root/Source/JavaScriptCore/dfg/DFGJITCompiler.cpp

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#include "config.h"
#include "DFGJITCompiler.h"

#if ENABLE(DFG_JIT)

#include "CodeBlock.h"
#include "DFGOSRExitCompiler.h"
#include "DFGOperations.h"
#include "DFGRegisterBank.h"
#include "DFGSlowPathGenerator.h"
#include "DFGSpeculativeJIT.h"
#include "DFGThunks.h"
#include "JSCJSValueInlines.h"
#include "VM.h"
#include "LinkBuffer.h"

namespace JSC { namespace DFG {

JITCompiler::JITCompiler(Graph& dfg)
    : CCallHelpers(&dfg.m_vm, dfg.m_codeBlock)
    , m_graph(dfg)
    , m_currentCodeOriginIndex(0)
{
    if (shouldShowDisassembly() || m_graph.m_vm.m_perBytecodeProfiler)
        m_disassembler = adoptPtr(new Disassembler(dfg));
}

void JITCompiler::linkOSRExits()
{
    ASSERT(codeBlock()->numberOfOSRExits() == m_exitCompilationInfo.size());
    if (m_graph.m_compilation) {
        for (unsigned i = 0; i < codeBlock()->numberOfOSRExits(); ++i) {
            OSRExit& exit = codeBlock()->osrExit(i);
            Vector<Label> labels;
            if (exit.m_watchpointIndex == std::numeric_limits<unsigned>::max()) {
                OSRExitCompilationInfo& info = m_exitCompilationInfo[i];
                for (unsigned j = 0; j < info.m_failureJumps.jumps().size(); ++j)
                    labels.append(info.m_failureJumps.jumps()[j].label());
            } else
                labels.append(codeBlock()->watchpoint(exit.m_watchpointIndex).sourceLabel());
            m_exitSiteLabels.append(labels);
        }
    }
    
    for (unsigned i = 0; i < codeBlock()->numberOfOSRExits(); ++i) {
        OSRExit& exit = codeBlock()->osrExit(i);
        JumpList& failureJumps = m_exitCompilationInfo[i].m_failureJumps;
        ASSERT(failureJumps.empty() == (exit.m_watchpointIndex != std::numeric_limits<unsigned>::max()));
        if (exit.m_watchpointIndex == std::numeric_limits<unsigned>::max())
            failureJumps.link(this);
        else
            codeBlock()->watchpoint(exit.m_watchpointIndex).setDestination(label());
        jitAssertHasValidCallFrame();
        store32(TrustedImm32(i), &vm()->osrExitIndex);
        exit.setPatchableCodeOffset(patchableJump());
    }
}

void JITCompiler::compileEntry()
{
    // This code currently matches the old JIT. In the function header we need to
    // pop the return address (since we do not allow any recursion on the machine
    // stack), and perform a fast stack check.
    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=56292
    // We'll need to convert the remaining cti_ style calls (specifically the stack
    // check) which will be dependent on stack layout. (We'd need to account for this in
    // both normal return code and when jumping to an exception handler).
    preserveReturnAddressAfterCall(GPRInfo::regT2);
    emitPutToCallFrameHeader(GPRInfo::regT2, JSStack::ReturnPC);
    emitPutImmediateToCallFrameHeader(m_codeBlock, JSStack::CodeBlock);
}

void JITCompiler::compileBody(SpeculativeJIT& speculative)
{
    // We generate the speculative code path, followed by OSR exit code to return
    // to the old JIT code if speculations fail.

#if DFG_ENABLE(JIT_BREAK_ON_EVERY_FUNCTION)
    // Handy debug tool!
    breakpoint();
#endif
    
    bool compiledSpeculative = speculative.compile();
    ASSERT_UNUSED(compiledSpeculative, compiledSpeculative);
}

void JITCompiler::compileExceptionHandlers()
{
    // Iterate over the m_calls vector, checking for jumps to link.
    bool didLinkExceptionCheck = false;
    for (unsigned i = 0; i < m_exceptionChecks.size(); ++i) {
        Jump& exceptionCheck = m_exceptionChecks[i].m_exceptionCheck;
        if (exceptionCheck.isSet()) {
            exceptionCheck.link(this);
            didLinkExceptionCheck = true;
        }
    }

    // If any exception checks were linked, generate code to lookup a handler.
    if (didLinkExceptionCheck) {
        // lookupExceptionHandler is passed two arguments, exec (the CallFrame*), and
        // the index into the CodeBlock's callReturnIndexVector corresponding to the
        // call that threw the exception (this was set in nonPreservedNonReturnGPR, when
        // the exception check was planted).
        move(GPRInfo::nonPreservedNonReturnGPR, GPRInfo::argumentGPR1);
        move(GPRInfo::callFrameRegister, GPRInfo::argumentGPR0);
#if CPU(X86)
        // FIXME: should use the call abstraction, but this is currently in the SpeculativeJIT layer!
        poke(GPRInfo::argumentGPR0);
        poke(GPRInfo::argumentGPR1, 1);
#endif
        m_calls.append(CallLinkRecord(call(), lookupExceptionHandler));
        // lookupExceptionHandler leaves the handler CallFrame* in the returnValueGPR,
        // and the address of the handler in returnValueGPR2.
        jump(GPRInfo::returnValueGPR2);
    }
}

void JITCompiler::link(LinkBuffer& linkBuffer)
{
    // Link the code, populate data in CodeBlock data structures.
#if DFG_ENABLE(DEBUG_VERBOSE)
    dataLogF("JIT code for %p start at [%p, %p). Size = %zu.\n", m_codeBlock, linkBuffer.debugAddress(), static_cast<char*>(linkBuffer.debugAddress()) + linkBuffer.debugSize(), linkBuffer.debugSize());
#endif

    // Link all calls out from the JIT code to their respective functions.
    for (unsigned i = 0; i < m_calls.size(); ++i)
        linkBuffer.link(m_calls[i].m_call, m_calls[i].m_function);

    m_codeBlock->callReturnIndexVector().reserveCapacity(m_exceptionChecks.size());
    for (unsigned i = 0; i < m_exceptionChecks.size(); ++i) {
        unsigned returnAddressOffset = linkBuffer.returnAddressOffset(m_exceptionChecks[i].m_call);
        CodeOrigin codeOrigin = m_exceptionChecks[i].m_codeOrigin;
        while (codeOrigin.inlineCallFrame)
            codeOrigin = codeOrigin.inlineCallFrame->caller;
        unsigned exceptionInfo = codeOrigin.bytecodeIndex;
        m_codeBlock->callReturnIndexVector().append(CallReturnOffsetToBytecodeOffset(returnAddressOffset, exceptionInfo));
    }

    Vector<CodeOriginAtCallReturnOffset, 0, UnsafeVectorOverflow>& codeOrigins = m_codeBlock->codeOrigins();
    codeOrigins.resize(m_exceptionChecks.size());
    
    for (unsigned i = 0; i < m_exceptionChecks.size(); ++i) {
        CallExceptionRecord& record = m_exceptionChecks[i];
        unsigned returnAddressOffset = linkBuffer.returnAddressOffset(m_exceptionChecks[i].m_call);
        codeOrigins[i].codeOrigin = record.m_codeOrigin;
        codeOrigins[i].callReturnOffset = returnAddressOffset;
    }
    
    m_codeBlock->setNumberOfStructureStubInfos(m_propertyAccesses.size());
    for (unsigned i = 0; i < m_propertyAccesses.size(); ++i) {
        StructureStubInfo& info = m_codeBlock->structureStubInfo(i);
        CodeLocationCall callReturnLocation = linkBuffer.locationOf(m_propertyAccesses[i].m_slowPathGenerator->call());
        info.codeOrigin = m_propertyAccesses[i].m_codeOrigin;
        info.callReturnLocation = callReturnLocation;
        info.patch.dfg.deltaCheckImmToCall = differenceBetweenCodePtr(linkBuffer.locationOf(m_propertyAccesses[i].m_structureImm), callReturnLocation);
        info.patch.dfg.deltaCallToStructCheck = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_structureCheck));
#if USE(JSVALUE64)
        info.patch.dfg.deltaCallToLoadOrStore = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_loadOrStore));
#else
        info.patch.dfg.deltaCallToTagLoadOrStore = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_tagLoadOrStore));
        info.patch.dfg.deltaCallToPayloadLoadOrStore = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_payloadLoadOrStore));
#endif
        info.patch.dfg.deltaCallToSlowCase = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_slowPathGenerator->label()));
        info.patch.dfg.deltaCallToDone = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_done));
        info.patch.dfg.deltaCallToStorageLoad = differenceBetweenCodePtr(callReturnLocation, linkBuffer.locationOf(m_propertyAccesses[i].m_propertyStorageLoad));
        info.patch.dfg.baseGPR = m_propertyAccesses[i].m_baseGPR;
#if USE(JSVALUE64)
        info.patch.dfg.valueGPR = m_propertyAccesses[i].m_valueGPR;
#else
        info.patch.dfg.valueTagGPR = m_propertyAccesses[i].m_valueTagGPR;
        info.patch.dfg.valueGPR = m_propertyAccesses[i].m_valueGPR;
#endif
        m_propertyAccesses[i].m_usedRegisters.copyInfo(info.patch.dfg.usedRegisters);
        info.patch.dfg.registersFlushed = m_propertyAccesses[i].m_registerMode == PropertyAccessRecord::RegistersFlushed;
    }
    
    m_codeBlock->setNumberOfCallLinkInfos(m_jsCalls.size());
    for (unsigned i = 0; i < m_jsCalls.size(); ++i) {
        CallLinkInfo& info = m_codeBlock->callLinkInfo(i);
        info.callType = m_jsCalls[i].m_callType;
        info.isDFG = true;
        info.codeOrigin = m_jsCalls[i].m_codeOrigin;
        linkBuffer.link(m_jsCalls[i].m_slowCall, FunctionPtr((m_vm->getCTIStub(info.callType == CallLinkInfo::Construct ? linkConstructThunkGenerator : linkCallThunkGenerator)).code().executableAddress()));
        info.callReturnLocation = linkBuffer.locationOfNearCall(m_jsCalls[i].m_slowCall);
        info.hotPathBegin = linkBuffer.locationOf(m_jsCalls[i].m_targetToCheck);
        info.hotPathOther = linkBuffer.locationOfNearCall(m_jsCalls[i].m_fastCall);
        info.calleeGPR = static_cast<unsigned>(m_jsCalls[i].m_callee);
    }
    
    MacroAssemblerCodeRef osrExitThunk = vm()->getCTIStub(osrExitGenerationThunkGenerator);
    CodeLocationLabel target = CodeLocationLabel(osrExitThunk.code());
    for (unsigned i = 0; i < codeBlock()->numberOfOSRExits(); ++i) {
        OSRExit& exit = codeBlock()->osrExit(i);
        linkBuffer.link(exit.getPatchableCodeOffsetAsJump(), target);
        exit.correctJump(linkBuffer);
        if (exit.m_watchpointIndex != std::numeric_limits<unsigned>::max())
            codeBlock()->watchpoint(exit.m_watchpointIndex).correctLabels(linkBuffer);
    }
    
    if (m_graph.m_compilation) {
        ASSERT(m_exitSiteLabels.size() == codeBlock()->numberOfOSRExits());
        for (unsigned i = 0; i < m_exitSiteLabels.size(); ++i) {
            Vector<Label>& labels = m_exitSiteLabels[i];
            Vector<const void*> addresses;
            for (unsigned j = 0; j < labels.size(); ++j)
                addresses.append(linkBuffer.locationOf(labels[j]).executableAddress());
            m_graph.m_compilation->addOSRExitSite(addresses);
        }
    } else
        ASSERT(!m_exitSiteLabels.size());
    
    codeBlock()->saveCompilation(m_graph.m_compilation);
}

bool JITCompiler::compile(JITCode& entry)
{
    SamplingRegion samplingRegion("DFG Backend");

    setStartOfCode();
    compileEntry();
    SpeculativeJIT speculative(*this);
    compileBody(speculative);
    setEndOfMainPath();

    // Generate slow path code.
    speculative.runSlowPathGenerators();
    
    compileExceptionHandlers();
    linkOSRExits();
    
    // Create OSR entry trampolines if necessary.
    speculative.createOSREntries();
    setEndOfCode();

    LinkBuffer linkBuffer(*m_vm, this, m_codeBlock, JITCompilationCanFail);
    if (linkBuffer.didFailToAllocate())
        return false;
    link(linkBuffer);
    speculative.linkOSREntries(linkBuffer);
    codeBlock()->shrinkToFit(CodeBlock::LateShrink);

    if (shouldShowDisassembly())
        m_disassembler->dump(linkBuffer);
    if (m_graph.m_compilation)
        m_disassembler->reportToProfiler(m_graph.m_compilation.get(), linkBuffer);

    entry = JITCode(
        linkBuffer.finalizeCodeWithoutDisassembly(),
        JITCode::DFGJIT);
    return true;
}

bool JITCompiler::compileFunction(JITCode& entry, MacroAssemblerCodePtr& entryWithArityCheck)
{
    SamplingRegion samplingRegion("DFG Backend");
    
    setStartOfCode();
    compileEntry();

    // === Function header code generation ===
    // This is the main entry point, without performing an arity check.
    // If we needed to perform an arity check we will already have moved the return address,
    // so enter after this.
    Label fromArityCheck(this);
    // Plant a check that sufficient space is available in the JSStack.
    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=56291
    addPtr(TrustedImm32(m_codeBlock->m_numCalleeRegisters * sizeof(Register)), GPRInfo::callFrameRegister, GPRInfo::regT1);
    Jump stackCheck = branchPtr(Below, AbsoluteAddress(m_vm->interpreter->stack().addressOfEnd()), GPRInfo::regT1);
    // Return here after stack check.
    Label fromStackCheck = label();


    // === Function body code generation ===
    SpeculativeJIT speculative(*this);
    compileBody(speculative);
    setEndOfMainPath();

    // === Function footer code generation ===
    //
    // Generate code to perform the slow stack check (if the fast one in
    // the function header fails), and generate the entry point with arity check.
    //
    // Generate the stack check; if the fast check in the function head fails,
    // we need to call out to a helper function to check whether more space is available.
    // FIXME: change this from a cti call to a DFG style operation (normal C calling conventions).
    stackCheck.link(this);
    move(stackPointerRegister, GPRInfo::argumentGPR0);
    poke(GPRInfo::callFrameRegister, OBJECT_OFFSETOF(struct JITStackFrame, callFrame) / sizeof(void*));

    CallBeginToken token;
    beginCall(CodeOrigin(0), token);
    Call callStackCheck = call();
    notifyCall(callStackCheck, CodeOrigin(0), token);
    jump(fromStackCheck);
    
    // The fast entry point into a function does not check the correct number of arguments
    // have been passed to the call (we only use the fast entry point where we can statically
    // determine the correct number of arguments have been passed, or have already checked).
    // In cases where an arity check is necessary, we enter here.
    // FIXME: change this from a cti call to a DFG style operation (normal C calling conventions).
    Label arityCheck = label();
    compileEntry();

    load32(AssemblyHelpers::payloadFor((VirtualRegister)JSStack::ArgumentCount), GPRInfo::regT1);
    branch32(AboveOrEqual, GPRInfo::regT1, TrustedImm32(m_codeBlock->numParameters())).linkTo(fromArityCheck, this);
    move(stackPointerRegister, GPRInfo::argumentGPR0);
    poke(GPRInfo::callFrameRegister, OBJECT_OFFSETOF(struct JITStackFrame, callFrame) / sizeof(void*));
    beginCall(CodeOrigin(0), token);
    Call callArityCheck = call();
    notifyCall(callArityCheck, CodeOrigin(0), token);
    move(GPRInfo::regT0, GPRInfo::callFrameRegister);
    jump(fromArityCheck);
    
    // Generate slow path code.
    speculative.runSlowPathGenerators();
    
    compileExceptionHandlers();
    linkOSRExits();
    
    // Create OSR entry trampolines if necessary.
    speculative.createOSREntries();
    setEndOfCode();

    // === Link ===
    LinkBuffer linkBuffer(*m_vm, this, m_codeBlock, JITCompilationCanFail);
    if (linkBuffer.didFailToAllocate())
        return false;
    link(linkBuffer);
    speculative.linkOSREntries(linkBuffer);
    codeBlock()->shrinkToFit(CodeBlock::LateShrink);
    
    // FIXME: switch the stack check & arity check over to DFGOpertaion style calls, not JIT stubs.
    linkBuffer.link(callStackCheck, cti_stack_check);
    linkBuffer.link(callArityCheck, m_codeBlock->m_isConstructor ? cti_op_construct_arityCheck : cti_op_call_arityCheck);
    
    if (shouldShowDisassembly())
        m_disassembler->dump(linkBuffer);
    if (m_graph.m_compilation)
        m_disassembler->reportToProfiler(m_graph.m_compilation.get(), linkBuffer);

    entryWithArityCheck = linkBuffer.locationOf(arityCheck);
    entry = JITCode(
        linkBuffer.finalizeCodeWithoutDisassembly(),
        JITCode::DFGJIT);
    return true;
}

} } // namespace JSC::DFG

#endif // ENABLE(DFG_JIT)