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/*
* Copyright (C) 2011-2021 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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"
#include "DFGOSRExit.h"
#if ENABLE(DFG_JIT)
#include "AssemblyHelpersSpoolers.h"
#include "BytecodeStructs.h"
#include "CheckpointOSRExitSideState.h"
#include "DFGGraph.h"
#include "DFGMayExit.h"
#include "DFGOSRExitCompilerCommon.h"
#include "DFGOperations.h"
#include "DFGSpeculativeJIT.h"
#include "FrameTracers.h"
#include "InlineCallFrame.h"
#include "JSCJSValueInlines.h"
#include "OperandsInlines.h"
#include "ProbeContext.h"
#include "VMInlines.h"
#include <wtf/Scope.h>
namespace JSC { namespace DFG {
OSRExit::OSRExit(ExitKind kind, JSValueSource jsValueSource, MethodOfGettingAValueProfile valueProfile, SpeculativeJIT* jit, unsigned streamIndex, unsigned recoveryIndex)
: OSRExitBase(kind, jit->m_origin.forExit, jit->m_origin.semantic, jit->m_origin.wasHoisted, jit->m_currentNode ? jit->m_currentNode->index() : 0)
, m_jsValueSource(jsValueSource)
, m_valueProfile(valueProfile)
, m_recoveryIndex(recoveryIndex)
, m_streamIndex(streamIndex)
{
bool canExit = jit->m_origin.exitOK;
if (!canExit && jit->m_currentNode) {
ExitMode exitMode = mayExit(jit->m_jit.graph(), jit->m_currentNode);
canExit = exitMode == ExitMode::Exits || exitMode == ExitMode::ExitsForExceptions;
}
DFG_ASSERT(jit->m_jit.graph(), jit->m_currentNode, canExit);
}
CodeLocationJump<JSInternalPtrTag> OSRExit::codeLocationForRepatch() const
{
return CodeLocationJump<JSInternalPtrTag>(m_patchableJumpLocation);
}
void OSRExit::emitRestoreArguments(CCallHelpers& jit, VM& vm, const Operands<ValueRecovery>& operands)
{
HashMap<MinifiedID, VirtualRegister> alreadyAllocatedArguments; // Maps phantom arguments node ID to operand.
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
if (recovery.technique() != DirectArgumentsThatWereNotCreated
&& recovery.technique() != ClonedArgumentsThatWereNotCreated)
continue;
Operand operand = operands.operandForIndex(index);
if (operand.isTmp())
continue;
MinifiedID id = recovery.nodeID();
auto iter = alreadyAllocatedArguments.find(id);
if (iter != alreadyAllocatedArguments.end()) {
JSValueRegs regs = JSValueRegs::withTwoAvailableRegs(GPRInfo::regT0, GPRInfo::regT1);
jit.loadValue(CCallHelpers::addressFor(iter->value), regs);
jit.storeValue(regs, CCallHelpers::addressFor(operand));
continue;
}
InlineCallFrame* inlineCallFrame =
jit.codeBlock()->jitCode()->dfg()->minifiedDFG.at(id)->inlineCallFrame();
int stackOffset;
if (inlineCallFrame)
stackOffset = inlineCallFrame->stackOffset;
else
stackOffset = 0;
if (!inlineCallFrame || inlineCallFrame->isClosureCall) {
jit.loadPtr(
AssemblyHelpers::addressFor(VirtualRegister(stackOffset + CallFrameSlot::callee)),
GPRInfo::regT0);
} else {
jit.move(
AssemblyHelpers::TrustedImmPtr(inlineCallFrame->calleeRecovery.constant().asCell()),
GPRInfo::regT0);
}
if (!inlineCallFrame || inlineCallFrame->isVarargs()) {
jit.load32(
AssemblyHelpers::payloadFor(VirtualRegister(stackOffset + CallFrameSlot::argumentCountIncludingThis)),
GPRInfo::regT1);
} else {
jit.move(
AssemblyHelpers::TrustedImm32(inlineCallFrame->argumentCountIncludingThis),
GPRInfo::regT1);
}
static_assert(std::is_same<decltype(operationCreateDirectArgumentsDuringExit), decltype(operationCreateClonedArgumentsDuringExit)>::value, "We assume these functions have the same signature below.");
jit.setupArguments<decltype(operationCreateDirectArgumentsDuringExit)>(
AssemblyHelpers::TrustedImmPtr(&vm), AssemblyHelpers::TrustedImmPtr(inlineCallFrame), GPRInfo::regT0, GPRInfo::regT1);
jit.prepareCallOperation(vm);
switch (recovery.technique()) {
case DirectArgumentsThatWereNotCreated:
jit.move(AssemblyHelpers::TrustedImmPtr(tagCFunction<OperationPtrTag>(operationCreateDirectArgumentsDuringExit)), GPRInfo::nonArgGPR0);
break;
case ClonedArgumentsThatWereNotCreated:
jit.move(AssemblyHelpers::TrustedImmPtr(tagCFunction<OperationPtrTag>(operationCreateClonedArgumentsDuringExit)), GPRInfo::nonArgGPR0);
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
jit.call(GPRInfo::nonArgGPR0, OperationPtrTag);
jit.storeCell(GPRInfo::returnValueGPR, AssemblyHelpers::addressFor(operand));
alreadyAllocatedArguments.add(id, operand.virtualRegister());
}
}
JSC_DEFINE_JIT_OPERATION(operationCompileOSRExit, void, (CallFrame* callFrame, void* bufferToPreserve))
{
VM& vm = callFrame->deprecatedVM();
auto scope = DECLARE_THROW_SCOPE(vm);
ActiveScratchBufferScope activeScratchBufferScope(ScratchBuffer::fromData(bufferToPreserve), GPRInfo::numberOfRegisters + FPRInfo::numberOfRegisters);
if constexpr (validateDFGDoesGC) {
// We're about to exit optimized code. So, there's no longer any optimized
// code running that expects no GC.
vm.setDoesGCExpectation(true, DoesGCCheck::Special::DFGOSRExit);
}
if (vm.callFrameForCatch)
RELEASE_ASSERT(vm.callFrameForCatch == callFrame);
CodeBlock* codeBlock = callFrame->codeBlock();
ASSERT(codeBlock);
ASSERT(codeBlock->jitType() == JITType::DFGJIT);
// It's sort of preferable that we don't GC while in here. Anyways, doing so wouldn't
// really be profitable.
DeferGCForAWhile deferGC(vm);
uint32_t exitIndex = vm.osrExitIndex;
OSRExit& exit = codeBlock->jitCode()->dfg()->m_osrExit[exitIndex];
ASSERT(!vm.callFrameForCatch || exit.m_kind == GenericUnwind);
EXCEPTION_ASSERT_UNUSED(scope, !!scope.exception() || !exit.isExceptionHandler());
// Compute the value recoveries.
Operands<ValueRecovery> operands;
codeBlock->jitCode()->dfg()->variableEventStream.reconstruct(codeBlock, exit.m_codeOrigin, codeBlock->jitCode()->dfg()->minifiedDFG, exit.m_streamIndex, operands);
SpeculationRecovery* recovery = nullptr;
if (exit.m_recoveryIndex != UINT_MAX)
recovery = &codeBlock->jitCode()->dfg()->m_speculationRecovery[exit.m_recoveryIndex];
{
CCallHelpers jit(codeBlock);
if (exit.m_kind == GenericUnwind) {
// We are acting as a defacto op_catch because we arrive here from genericUnwind().
// So, we must restore our call frame and stack pointer.
jit.restoreCalleeSavesFromEntryFrameCalleeSavesBuffer(vm.topEntryFrame);
jit.loadPtr(vm.addressOfCallFrameForCatch(), GPRInfo::callFrameRegister);
}
jit.addPtr(
CCallHelpers::TrustedImm32(codeBlock->stackPointerOffset() * sizeof(Register)),
GPRInfo::callFrameRegister, CCallHelpers::stackPointerRegister);
jit.jitAssertHasValidCallFrame();
if (UNLIKELY(vm.m_perBytecodeProfiler && codeBlock->jitCode()->dfgCommon()->compilation)) {
Profiler::Database& database = *vm.m_perBytecodeProfiler;
Profiler::Compilation* compilation = codeBlock->jitCode()->dfgCommon()->compilation.get();
Profiler::OSRExit* profilerExit = compilation->addOSRExit(
exitIndex, Profiler::OriginStack(database, codeBlock, exit.m_codeOrigin),
exit.m_kind, exit.m_kind == UncountableInvalidation);
jit.add64(CCallHelpers::TrustedImm32(1), CCallHelpers::AbsoluteAddress(profilerExit->counterAddress()));
}
OSRExit::compileExit(jit, vm, exit, operands, recovery);
LinkBuffer patchBuffer(jit, codeBlock, LinkBuffer::Profile::DFGOSRExit);
exit.m_code = FINALIZE_CODE_IF(
shouldDumpDisassembly() || Options::verboseOSR() || Options::verboseDFGOSRExit(),
patchBuffer, OSRExitPtrTag,
"DFG OSR exit #%u (D@%u, %s, %s) from %s, with operands = %s",
exitIndex, exit.m_dfgNodeIndex, toCString(exit.m_codeOrigin).data(),
exitKindToString(exit.m_kind), toCString(*codeBlock).data(),
toCString(ignoringContext<DumpContext>(operands)).data());
}
MacroAssembler::repatchJump(exit.codeLocationForRepatch(), CodeLocationLabel<OSRExitPtrTag>(exit.m_code.code()));
vm.osrExitJumpDestination = exit.m_code.code().executableAddress();
}
IGNORE_WARNINGS_BEGIN("frame-address")
JSC_DEFINE_JIT_OPERATION(operationMaterializeOSRExitSideState, void, (VM* vmPointer, const OSRExitBase* exitPointer, EncodedJSValue* tmpScratch))
{
const OSRExitBase& exit = *exitPointer;
VM& vm = *vmPointer;
CallFrame* callFrame = DECLARE_CALL_FRAME(vm);
Vector<std::unique_ptr<CheckpointOSRExitSideState>, VM::expectedMaxActiveSideStateCount> sideStates;
sideStates.reserveInitialCapacity(exit.m_codeOrigin.inlineDepth());
auto sideStateCommitter = makeScopeExit([&] {
for (size_t i = sideStates.size(); i--;)
vm.pushCheckpointOSRSideState(WTFMove(sideStates[i]));
});
auto addSideState = [&] (CallFrame* frame, BytecodeIndex index, size_t tmpOffset) {
std::unique_ptr<CheckpointOSRExitSideState> sideState = WTF::makeUnique<CheckpointOSRExitSideState>(frame);
sideState->bytecodeIndex = index;
for (size_t i = 0; i < maxNumCheckpointTmps; ++i)
sideState->tmps[i] = JSValue::decode(tmpScratch[i + tmpOffset]);
sideStates.append(WTFMove(sideState));
};
const CodeOrigin* codeOrigin;
for (codeOrigin = &exit.m_codeOrigin; codeOrigin && codeOrigin->inlineCallFrame(); codeOrigin = codeOrigin->inlineCallFrame()->getCallerSkippingTailCalls()) {
BytecodeIndex callBytecodeIndex = codeOrigin->bytecodeIndex();
if (!callBytecodeIndex.checkpoint())
continue;
auto* inlineCallFrame = codeOrigin->inlineCallFrame();
addSideState(reinterpret_cast_ptr<CallFrame*>(reinterpret_cast<char*>(callFrame) + inlineCallFrame->returnPCOffset() - sizeof(CPURegister)), callBytecodeIndex, inlineCallFrame->tmpOffset);
}
if (!codeOrigin)
return;
if (BytecodeIndex bytecodeIndex = codeOrigin->bytecodeIndex(); bytecodeIndex.checkpoint())
addSideState(callFrame, bytecodeIndex, 0);
}
IGNORE_WARNINGS_END
void OSRExit::compileExit(CCallHelpers& jit, VM& vm, const OSRExit& exit, const Operands<ValueRecovery>& operands, SpeculationRecovery* recovery)
{
jit.jitAssertTagsInPlace();
// Pro-forma stuff.
if (UNLIKELY(Options::printEachOSRExit())) {
SpeculationFailureDebugInfo* debugInfo = new SpeculationFailureDebugInfo;
debugInfo->codeBlock = jit.codeBlock();
debugInfo->kind = exit.m_kind;
debugInfo->bytecodeIndex = exit.m_codeOrigin.bytecodeIndex();
jit.debugCall(vm, operationDebugPrintSpeculationFailure, debugInfo);
}
// Perform speculation recovery. This only comes into play when an operation
// starts mutating state before verifying the speculation it has already made.
if (recovery) {
switch (recovery->type()) {
case SpeculativeAdd:
jit.sub32(recovery->src(), recovery->dest());
#if USE(JSVALUE64)
jit.or64(GPRInfo::numberTagRegister, recovery->dest());
#endif
break;
case SpeculativeAddSelf:
// If A + A = A (int32_t) overflows, A can be recovered by ((static_cast<int32_t>(A) >> 1) ^ 0x8000000).
jit.rshift32(AssemblyHelpers::TrustedImm32(1), recovery->dest());
jit.xor32(AssemblyHelpers::TrustedImm32(0x80000000), recovery->dest());
#if USE(JSVALUE64)
jit.or64(GPRInfo::numberTagRegister, recovery->dest());
#endif
break;
case SpeculativeAddImmediate:
jit.sub32(AssemblyHelpers::Imm32(recovery->immediate()), recovery->dest());
#if USE(JSVALUE64)
jit.or64(GPRInfo::numberTagRegister, recovery->dest());
#endif
break;
case BooleanSpeculationCheck:
#if USE(JSVALUE64)
jit.xor64(AssemblyHelpers::TrustedImm32(JSValue::ValueFalse), recovery->dest());
#endif
break;
default:
break;
}
}
// Refine some array and/or value profile, if appropriate.
if (!!exit.m_jsValueSource) {
if (exit.m_kind == BadCache || exit.m_kind == BadIndexingType) {
// If the instruction that this originated from has an array profile, then
// refine it. If it doesn't, then do nothing. The latter could happen for
// hoisted checks, or checks emitted for operations that didn't have array
// profiling - either ops that aren't array accesses at all, or weren't
// known to be array acceses in the bytecode. The latter case is a FIXME
// while the former case is an outcome of a CheckStructure not knowing why
// it was emitted (could be either due to an inline cache of a property
// property access, or due to an array profile).
CodeOrigin codeOrigin = exit.m_codeOriginForExitProfile;
CodeBlock* codeBlock = jit.baselineCodeBlockFor(codeOrigin);
if (ArrayProfile* arrayProfile = codeBlock->getArrayProfile(codeOrigin.bytecodeIndex())) {
const Instruction* instruction = codeBlock->instructions().at(codeOrigin.bytecodeIndex()).ptr();
CCallHelpers::Jump skipProfile;
if (instruction->is<OpGetById>()) {
auto& metadata = instruction->as<OpGetById>().metadata(codeBlock);
skipProfile = jit.branch8(CCallHelpers::NotEqual, CCallHelpers::AbsoluteAddress(&metadata.m_modeMetadata.mode), CCallHelpers::TrustedImm32(static_cast<uint8_t>(GetByIdMode::ArrayLength)));
}
#if USE(JSVALUE64)
GPRReg usedRegister;
if (exit.m_jsValueSource.isAddress())
usedRegister = exit.m_jsValueSource.base();
else
usedRegister = exit.m_jsValueSource.gpr();
#else
GPRReg usedRegister1;
GPRReg usedRegister2;
if (exit.m_jsValueSource.isAddress()) {
usedRegister1 = exit.m_jsValueSource.base();
usedRegister2 = InvalidGPRReg;
} else {
usedRegister1 = exit.m_jsValueSource.payloadGPR();
if (exit.m_jsValueSource.hasKnownTag())
usedRegister2 = InvalidGPRReg;
else
usedRegister2 = exit.m_jsValueSource.tagGPR();
}
#endif
GPRReg scratch1;
GPRReg scratch2;
#if USE(JSVALUE64)
scratch1 = AssemblyHelpers::selectScratchGPR(usedRegister);
scratch2 = AssemblyHelpers::selectScratchGPR(usedRegister, scratch1);
#else
scratch1 = AssemblyHelpers::selectScratchGPR(usedRegister1, usedRegister2);
scratch2 = AssemblyHelpers::selectScratchGPR(usedRegister1, usedRegister2, scratch1);
#endif
if (isARM64()) {
jit.pushToSave(scratch1);
jit.pushToSave(scratch2);
} else {
jit.push(scratch1);
jit.push(scratch2);
}
GPRReg value;
if (exit.m_jsValueSource.isAddress()) {
value = scratch1;
jit.loadPtr(AssemblyHelpers::Address(exit.m_jsValueSource.asAddress()), value);
} else
value = exit.m_jsValueSource.payloadGPR();
jit.load32(AssemblyHelpers::Address(value, JSCell::structureIDOffset()), scratch1);
jit.store32(scratch1, arrayProfile->addressOfLastSeenStructureID());
jit.load8(AssemblyHelpers::Address(value, JSCell::typeInfoTypeOffset()), scratch2);
jit.sub32(AssemblyHelpers::TrustedImm32(FirstTypedArrayType), scratch2);
auto notTypedArray = jit.branch32(MacroAssembler::AboveOrEqual, scratch2, AssemblyHelpers::TrustedImm32(NumberOfTypedArrayTypesExcludingDataView));
jit.move(AssemblyHelpers::TrustedImmPtr(typedArrayModes), scratch1);
jit.load32(AssemblyHelpers::BaseIndex(scratch1, scratch2, AssemblyHelpers::TimesFour), scratch2);
auto storeArrayModes = jit.jump();
notTypedArray.link(&jit);
#if USE(JSVALUE64)
jit.load8(AssemblyHelpers::Address(value, JSCell::indexingTypeAndMiscOffset()), scratch1);
#else
jit.load8(AssemblyHelpers::Address(scratch1, Structure::indexingModeIncludingHistoryOffset()), scratch1);
#endif
jit.and32(AssemblyHelpers::TrustedImm32(IndexingModeMask), scratch1);
jit.move(AssemblyHelpers::TrustedImm32(1), scratch2);
jit.lshift32(scratch1, scratch2);
storeArrayModes.link(&jit);
jit.or32(scratch2, AssemblyHelpers::AbsoluteAddress(arrayProfile->addressOfArrayModes()));
if (isARM64()) {
jit.popToRestore(scratch2);
jit.popToRestore(scratch1);
} else {
jit.pop(scratch2);
jit.pop(scratch1);
}
if (skipProfile.isSet())
skipProfile.link(&jit);
}
}
if (MethodOfGettingAValueProfile profile = exit.m_valueProfile) {
#if USE(JSVALUE64)
if (exit.m_jsValueSource.isAddress()) {
// We can't be sure that we have a spare register. So use the numberTagRegister,
// since we know how to restore it.
jit.load64(AssemblyHelpers::Address(exit.m_jsValueSource.asAddress()), GPRInfo::numberTagRegister);
// We also use the notCellMaskRegister as the scratch register, for the same reason.
// FIXME: find a less gross way of doing this, maybe through delaying these operations until we actually have some spare registers around?
profile.emitReportValue(jit, JSValueRegs(GPRInfo::numberTagRegister), GPRInfo::notCellMaskRegister, DoNotHaveTagRegisters);
jit.move(AssemblyHelpers::TrustedImm64(JSValue::NumberTag), GPRInfo::numberTagRegister);
} else
profile.emitReportValue(jit, JSValueRegs(exit.m_jsValueSource.gpr()), GPRInfo::notCellMaskRegister, DoNotHaveTagRegisters);
jit.move(AssemblyHelpers::TrustedImm64(JSValue::NotCellMask), GPRInfo::notCellMaskRegister);
#else // not USE(JSVALUE64)
if (exit.m_jsValueSource.isAddress()) {
// Save a register so we can use it.
GPRReg scratchPayload = AssemblyHelpers::selectScratchGPR(exit.m_jsValueSource.base());
GPRReg scratchTag = AssemblyHelpers::selectScratchGPR(exit.m_jsValueSource.base(), scratchPayload);
jit.pushToSave(scratchPayload);
jit.pushToSave(scratchTag);
JSValueRegs scratch(scratchTag, scratchPayload);
jit.loadValue(exit.m_jsValueSource.asAddress(), scratch);
profile.emitReportValue(jit, scratch, InvalidGPRReg);
jit.popToRestore(scratchTag);
jit.popToRestore(scratchPayload);
} else if (exit.m_jsValueSource.hasKnownTag()) {
GPRReg scratchTag = AssemblyHelpers::selectScratchGPR(exit.m_jsValueSource.payloadGPR());
jit.pushToSave(scratchTag);
jit.move(AssemblyHelpers::TrustedImm32(exit.m_jsValueSource.tag()), scratchTag);
JSValueRegs value(scratchTag, exit.m_jsValueSource.payloadGPR());
profile.emitReportValue(jit, value, InvalidGPRReg);
jit.popToRestore(scratchTag);
} else
profile.emitReportValue(jit, exit.m_jsValueSource.regs(), InvalidGPRReg);
#endif // USE(JSVALUE64)
}
}
// What follows is an intentionally simple OSR exit implementation that generates
// fairly poor code but is very easy to hack. In particular, it dumps all state that
// needs conversion into a scratch buffer so that in step 6, where we actually do the
// conversions, we know that all temp registers are free to use and the variable is
// definitely in a well-known spot in the scratch buffer regardless of whether it had
// originally been in a register or spilled. This allows us to decouple "where was
// the variable" from "how was it represented". Consider that the
// Int32DisplacedInJSStack recovery: it tells us that the value is in a
// particular place and that that place holds an unboxed int32. We have two different
// places that a value could be (displaced, register) and a bunch of different
// ways of representing a value. The number of recoveries is two * a bunch. The code
// below means that we have to have two + a bunch cases rather than two * a bunch.
// Once we have loaded the value from wherever it was, the reboxing is the same
// regardless of its location. Likewise, before we do the reboxing, the way we get to
// the value (i.e. where we load it from) is the same regardless of its type. Because
// the code below always dumps everything into a scratch buffer first, the two
// questions become orthogonal, which simplifies adding new types and adding new
// locations.
//
// This raises the question: does using such a suboptimal implementation of OSR exit,
// where we always emit code to dump all state into a scratch buffer only to then
// dump it right back into the stack, hurt us in any way? The asnwer is that OSR exits
// are rare. Our tiering strategy ensures this. This is because if an OSR exit is
// taken more than ~100 times, we jettison the DFG code block along with all of its
// exits. It is impossible for an OSR exit - i.e. the code we compile below - to
// execute frequently enough for the codegen to matter that much. It probably matters
// enough that we don't want to turn this into some super-slow function call, but so
// long as we're generating straight-line code, that code can be pretty bad. Also
// because we tend to exit only along one OSR exit from any DFG code block - that's an
// empirical result that we're extremely confident about - the code size of this
// doesn't matter much. Hence any attempt to optimize the codegen here is just purely
// harmful to the system: it probably won't reduce either net memory usage or net
// execution time. It will only prevent us from cleanly decoupling "where was the
// variable" from "how was it represented", which will make it more difficult to add
// features in the future and it will make it harder to reason about bugs.
// Save all state from GPRs into the scratch buffer.
ScratchBuffer* scratchBuffer = vm.scratchBufferForSize(sizeof(EncodedJSValue) * operands.size());
EncodedJSValue* scratch = scratchBuffer ? static_cast<EncodedJSValue*>(scratchBuffer->dataBuffer()) : nullptr;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case UnboxedInt32InGPR:
case UnboxedCellInGPR:
#if USE(JSVALUE64)
case InGPR:
case UnboxedInt52InGPR:
case UnboxedStrictInt52InGPR:
jit.store64(recovery.gpr(), scratch + index);
break;
#else
case UnboxedBooleanInGPR:
jit.store32(
recovery.gpr(),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload);
break;
case InPair:
jit.storeValue(recovery.jsValueRegs(), scratch + index);
break;
#endif
default:
break;
}
}
// And voila, all GPRs are free to reuse.
// Save all state from FPRs into the scratch buffer.
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case UnboxedDoubleInFPR:
case InFPR:
jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT0);
jit.storeDouble(recovery.fpr(), MacroAssembler::Address(GPRInfo::regT0));
break;
default:
break;
}
}
// Now, all FPRs are also free.
// Save all state from the stack into the scratch buffer. For simplicity we
// do this even for state that's already in the right place on the stack.
// It makes things simpler later.
bool inlineStackContainsActiveCheckpoint = exit.m_codeOrigin.inlineStackContainsActiveCheckpoint();
size_t firstTmpToRestoreEarly = operands.size() - operands.numberOfTmps();
if (!inlineStackContainsActiveCheckpoint)
firstTmpToRestoreEarly = operands.size(); // Don't eagerly restore.
// The tag registers are needed to materialize recoveries below.
jit.emitMaterializeTagCheckRegisters();
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
auto currentTechnique = recovery.technique();
switch (currentTechnique) {
case DisplacedInJSStack:
#if USE(JSVALUE64)
case CellDisplacedInJSStack:
case BooleanDisplacedInJSStack:
#endif
jit.loadValue(AssemblyHelpers::addressFor(recovery.virtualRegister()), JSRInfo::jsRegT10);
jit.storeValue(JSRInfo::jsRegT10, scratch + index);
break;
case Constant: {
#if USE(JSVALUE64)
if (index >= firstTmpToRestoreEarly) {
ASSERT(operands.operandForIndex(index).isTmp());
jit.move(AssemblyHelpers::TrustedImm64(JSValue::encode(recovery.constant())), GPRInfo::regT0);
jit.store64(GPRInfo::regT0, scratch + index);
}
#else // not USE(JSVALUE64)
UNUSED_VARIABLE(firstTmpToRestoreEarly);
jit.storeValue(recovery.constant(), scratch + index, JSRInfo::jsRegT10);
#endif
break;
}
case UnboxedInt32InGPR:
#if USE(JSVALUE64)
jit.load64(scratch + index, GPRInfo::regT0);
jit.zeroExtend32ToWord(GPRInfo::regT0, GPRInfo::regT0);
jit.or64(GPRInfo::numberTagRegister, GPRInfo::regT0);
jit.store64(GPRInfo::regT0, scratch + index);
#else
jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::Int32Tag),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag);
#endif
break;
case Int32DisplacedInJSStack:
#if USE(JSVALUE64)
jit.load64(AssemblyHelpers::addressFor(recovery.virtualRegister()), GPRInfo::regT0);
jit.zeroExtend32ToWord(GPRInfo::regT0, GPRInfo::regT0);
jit.or64(GPRInfo::numberTagRegister, GPRInfo::regT0);
jit.store64(GPRInfo::regT0, scratch + index);
#else
jit.load32(
AssemblyHelpers::payloadFor(recovery.virtualRegister()),
JSRInfo::jsRegT10.payloadGPR());
jit.move(AssemblyHelpers::TrustedImm32(JSValue::Int32Tag), JSRInfo::jsRegT10.tagGPR());
jit.storeValue(JSRInfo::jsRegT10, scratch + index);
#endif
break;
#if USE(JSVALUE32_64)
case UnboxedBooleanInGPR:
jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::BooleanTag),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag);
break;
case BooleanDisplacedInJSStack:
jit.load32(
AssemblyHelpers::payloadFor(recovery.virtualRegister()),
JSRInfo::jsRegT10.payloadGPR());
jit.move(AssemblyHelpers::TrustedImm32(JSValue::BooleanTag), JSRInfo::jsRegT10.tagGPR());
jit.storeValue(JSRInfo::jsRegT10, scratch + index);
break;
case UnboxedCellInGPR:
jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::CellTag),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag);
break;
case CellDisplacedInJSStack:
jit.load32(
AssemblyHelpers::payloadFor(recovery.virtualRegister()),
JSRInfo::jsRegT10.payloadGPR());
jit.move(AssemblyHelpers::TrustedImm32(JSValue::CellTag), JSRInfo::jsRegT10.tagGPR());
jit.storeValue(JSRInfo::jsRegT10, scratch + index);
break;
#endif
case UnboxedDoubleInFPR:
jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT1);
jit.loadDouble(MacroAssembler::Address(GPRInfo::regT1), FPRInfo::fpRegT0);
jit.purifyNaN(FPRInfo::fpRegT0);
#if USE(JSVALUE64)
jit.boxDouble(FPRInfo::fpRegT0, GPRInfo::regT0);
jit.store64(GPRInfo::regT0, MacroAssembler::Address(GPRInfo::regT1));
#else
jit.storeDouble(FPRInfo::fpRegT0, MacroAssembler::Address(GPRInfo::regT1));
#endif
break;
case DoubleDisplacedInJSStack:
jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT1);
jit.loadDouble(AssemblyHelpers::addressFor(recovery.virtualRegister()), FPRInfo::fpRegT0);
jit.purifyNaN(FPRInfo::fpRegT0);
#if USE(JSVALUE64)
jit.boxDouble(FPRInfo::fpRegT0, GPRInfo::regT0);
jit.store64(GPRInfo::regT0, MacroAssembler::Address(GPRInfo::regT1));
#else
jit.storeDouble(FPRInfo::fpRegT0, MacroAssembler::Address(GPRInfo::regT1));
#endif
break;
#if USE(JSVALUE64)
case UnboxedInt52InGPR:
jit.load64(scratch + index, GPRInfo::regT0);
jit.rshift64(AssemblyHelpers::TrustedImm32(JSValue::int52ShiftAmount), GPRInfo::regT0);
jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
jit.store64(GPRInfo::regT0, scratch + index);
break;
case Int52DisplacedInJSStack:
jit.load64(AssemblyHelpers::addressFor(recovery.virtualRegister()), GPRInfo::regT0);
jit.rshift64(AssemblyHelpers::TrustedImm32(JSValue::int52ShiftAmount), GPRInfo::regT0);
jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
jit.store64(GPRInfo::regT0, scratch + index);
break;
case UnboxedStrictInt52InGPR:
jit.load64(scratch + index, GPRInfo::regT0);
jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
jit.store64(GPRInfo::regT0, scratch + index);
break;
case StrictInt52DisplacedInJSStack:
jit.load64(AssemblyHelpers::addressFor(recovery.virtualRegister()), GPRInfo::regT0);
jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
jit.store64(GPRInfo::regT0, scratch + index);
break;
#endif
default:
break;
}
}
if constexpr (validateDFGDoesGC) {
if (Options::validateDoesGC()) {
// We're about to exit optimized code. So, there's no longer any optimized
// code running that expects no GC. We need to set this before arguments
// materialization below (see emitRestoreArguments()).
// Even though we set Heap::m_doesGC in compileOSRExit(), we also need
// to set it here because compileOSRExit() is only called on the first time
// we exit from this site, but all subsequent exits will take this compiled
// ramp without calling compileOSRExit() first.
DoesGCCheck check;
check.u.encoded = DoesGCCheck::encode(true, DoesGCCheck::Special::DFGOSRExit);
#if USE(JSVALUE64)
jit.store64(CCallHelpers::TrustedImm64(check.u.encoded), vm.addressOfDoesGC());
#else
jit.store32(CCallHelpers::TrustedImm32(check.u.other), &vm.addressOfDoesGC()->u.other);
jit.store32(CCallHelpers::TrustedImm32(check.u.nodeIndex), &vm.addressOfDoesGC()->u.nodeIndex);
#endif
}
}
// Need to ensure that the stack pointer accounts for the worst-case stack usage at exit. This
// could toast some stack that the DFG used. We need to do it before storing to stack offsets
// used by baseline.
jit.addPtr(
CCallHelpers::TrustedImm32(
-jit.codeBlock()->jitCode()->dfgCommon()->requiredRegisterCountForExit * sizeof(Register)),
CCallHelpers::framePointerRegister, CCallHelpers::stackPointerRegister);
// Restore the DFG callee saves and then save the ones the baseline JIT uses.
jit.emitRestoreCalleeSavesFor(jit.codeBlock()->jitCode()->calleeSaveRegisters());
jit.emitSaveCalleeSavesFor(jit.baselineCodeBlock()->jitCode()->calleeSaveRegisters());
// The tag registers are needed to materialize recoveries below.
jit.emitMaterializeTagCheckRegisters();
if (inlineStackContainsActiveCheckpoint) {
EncodedJSValue* tmpScratch = scratch + operands.tmpIndex(0);
jit.setupArguments<decltype(operationMaterializeOSRExitSideState)>(&vm, &exit, tmpScratch);
jit.prepareCallOperation(vm);
jit.move(AssemblyHelpers::TrustedImmPtr(tagCFunction<OperationPtrTag>(operationMaterializeOSRExitSideState)), GPRInfo::nonArgGPR0);
jit.call(GPRInfo::nonArgGPR0, OperationPtrTag);
}
// Do all data format conversions and store the results into the stack.
#if USE(JSVALUE64)
constexpr GPRReg srcBufferGPR = GPRInfo::regT2;
constexpr GPRReg destBufferGPR = GPRInfo::regT3;
constexpr GPRReg undefinedGPR = GPRInfo::regT4;
bool undefinedGPRIsInitialized = false;
jit.move(CCallHelpers::TrustedImmPtr(scratch), srcBufferGPR);
jit.move(CCallHelpers::framePointerRegister, destBufferGPR);
CCallHelpers::CopySpooler spooler(CCallHelpers::CopySpooler::BufferRegs::AllowModification, jit, srcBufferGPR, destBufferGPR, GPRInfo::regT0, GPRInfo::regT1);
#endif
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
Operand operand = operands.operandForIndex(index);
if (operand.isTmp())
continue;
if (operand.isLocal() && operand.toLocal() < static_cast<int>(CodeBlock::calleeSaveSpaceAsVirtualRegisters(*jit.baselineCodeBlock()->jitCode()->calleeSaveRegisters())))
continue;
switch (recovery.technique()) {
case Constant: {
#if USE(JSVALUE64)
EncodedJSValue currentConstant = JSValue::encode(recovery.constant());
if (currentConstant == encodedJSUndefined()) {
if (!undefinedGPRIsInitialized) {
jit.move(CCallHelpers::TrustedImm64(encodedJSUndefined()), undefinedGPR);
undefinedGPRIsInitialized = true;
}
spooler.copyGPR(undefinedGPR);
} else
spooler.moveConstant(currentConstant);
spooler.storeGPR(operand.virtualRegister().offset() * sizeof(CPURegister));
break;
#else
FALLTHROUGH;
#endif
}
case DisplacedInJSStack:
case BooleanDisplacedInJSStack:
case Int32DisplacedInJSStack:
case CellDisplacedInJSStack:
case DoubleDisplacedInJSStack:
case UnboxedBooleanInGPR:
case UnboxedInt32InGPR:
case UnboxedCellInGPR:
case UnboxedDoubleInFPR:
case InFPR:
#if USE(JSVALUE64)
case InGPR:
case UnboxedInt52InGPR:
case Int52DisplacedInJSStack:
case UnboxedStrictInt52InGPR:
case StrictInt52DisplacedInJSStack:
spooler.loadGPR(index * sizeof(CPURegister));
spooler.storeGPR(operand.virtualRegister().offset() * sizeof(CPURegister));
break;
#else // not USE(JSVALUE64)
case InPair:
jit.loadValue(scratch + index, JSRInfo::jsRegT10);
jit.storeValue(JSRInfo::jsRegT10, AssemblyHelpers::addressFor(operand));
break;
#endif // USE(JSVALUE64)
case DirectArgumentsThatWereNotCreated:
case ClonedArgumentsThatWereNotCreated:
// Don't do this, yet.
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
}
#if USE(JSVALUE64)
spooler.finalizeGPR();
#endif
// Now that things on the stack are recovered, do the arguments recovery. We assume that arguments
// recoveries don't recursively refer to each other. But, we don't try to assume that they only
// refer to certain ranges of locals. Hence why we need to do this here, once the stack is sensible.
// Note that we also roughly assume that the arguments might still be materialized outside of its
// inline call frame scope - but for now the DFG wouldn't do that.
emitRestoreArguments(jit, vm, operands);
// Adjust the old JIT's execute counter. Since we are exiting OSR, we know
// that all new calls into this code will go to the new JIT, so the execute
// counter only affects call frames that performed OSR exit and call frames
// that were still executing the old JIT at the time of another call frame's
// OSR exit. We want to ensure that the following is true:
//
// (a) Code the performs an OSR exit gets a chance to reenter optimized
// code eventually, since optimized code is faster. But we don't
// want to do such reentery too aggressively (see (c) below).
//
// (b) If there is code on the call stack that is still running the old
// JIT's code and has never OSR'd, then it should get a chance to
// perform OSR entry despite the fact that we've exited.
//
// (c) Code the performs an OSR exit should not immediately retry OSR
// entry, since both forms of OSR are expensive. OSR entry is
// particularly expensive.
//
// (d) Frequent OSR failures, even those that do not result in the code
// running in a hot loop, result in recompilation getting triggered.
//
// To ensure (c), we'd like to set the execute counter to
// counterValueForOptimizeAfterWarmUp(). This seems like it would endanger
// (a) and (b), since then every OSR exit would delay the opportunity for
// every call frame to perform OSR entry. Essentially, if OSR exit happens
// frequently and the function has few loops, then the counter will never
// become non-negative and OSR entry will never be triggered. OSR entry
// will only happen if a loop gets hot in the old JIT, which does a pretty
// good job of ensuring (a) and (b). But that doesn't take care of (d),
// since each speculation failure would reset the execute counter.
// So we check here if the number of speculation failures is significantly
// larger than the number of successes (we want 90% success rate), and if
// there have been a large enough number of failures. If so, we set the
// counter to 0; otherwise we set the counter to
// counterValueForOptimizeAfterWarmUp().
handleExitCounts(vm, jit, exit);
// Reify inlined call frames.
reifyInlinedCallFrames(jit, exit);
// And finish.
adjustAndJumpToTarget(vm, jit, exit);
}
JSC_DEFINE_JIT_OPERATION(operationDebugPrintSpeculationFailure, void, (CallFrame* callFrame, void* debugInfoRaw, void* scratch))
{
VM& vm = callFrame->deprecatedVM();
NativeCallFrameTracer tracer(vm, callFrame);
ActiveScratchBufferScope activeScratchBufferScope(ScratchBuffer::fromData(scratch), GPRInfo::numberOfRegisters + FPRInfo::numberOfRegisters);
SpeculationFailureDebugInfo* debugInfo = static_cast<SpeculationFailureDebugInfo*>(debugInfoRaw);
CodeBlock* codeBlock = debugInfo->codeBlock;
CodeBlock* alternative = codeBlock->alternative();
dataLog("Speculation failure in ", *codeBlock);
dataLog(" @ exit #", vm.osrExitIndex, " (", debugInfo->bytecodeIndex, ", ", exitKindToString(debugInfo->kind), ") with ");
if (alternative) {
dataLog(
"executeCounter = ", alternative->jitExecuteCounter(),
", reoptimizationRetryCounter = ", alternative->reoptimizationRetryCounter(),
", optimizationDelayCounter = ", alternative->optimizationDelayCounter());
} else
dataLog("no alternative code block (i.e. we've been jettisoned)");
dataLog(", osrExitCounter = ", codeBlock->osrExitCounter(), "\n");
dataLog(" GPRs at time of exit:");
char* scratchPointer = static_cast<char*>(scratch);
for (unsigned i = 0; i < GPRInfo::numberOfRegisters; ++i) {
GPRReg gpr = GPRInfo::toRegister(i);
dataLog(" ", GPRInfo::debugName(gpr), ":", RawPointer(*reinterpret_cast_ptr<void**>(scratchPointer)));
scratchPointer += sizeof(EncodedJSValue);
}
dataLog("\n");
dataLog(" FPRs at time of exit:");
for (unsigned i = 0; i < FPRInfo::numberOfRegisters; ++i) {
FPRReg fpr = FPRInfo::toRegister(i);
dataLog(" ", FPRInfo::debugName(fpr), ":");
uint64_t bits = *reinterpret_cast_ptr<uint64_t*>(scratchPointer);
double value = *reinterpret_cast_ptr<double*>(scratchPointer);
dataLogF("%llx:%lf", static_cast<long long>(bits), value);
scratchPointer += sizeof(EncodedJSValue);
}
dataLog("\n");
}
} } // namespace JSC::DFG
#endif // ENABLE(DFG_JIT)