void OSRExitCompiler::compileExit(const OSRExit& exit, const Operands<ValueRecovery>& operands, SpeculationRecovery* recovery)
{
// 1) Pro-forma stuff.
if (Options::printEachOSRExit()) {
SpeculationFailureDebugInfo* debugInfo = new SpeculationFailureDebugInfo;
debugInfo->codeBlock = m_jit.codeBlock();
debugInfo->kind = exit.m_kind;
debugInfo->bytecodeOffset = exit.m_codeOrigin.bytecodeIndex;
m_jit.debugCall(debugOperationPrintSpeculationFailure, debugInfo);
}
// Need to ensure that the stack pointer accounts for the worst-case stack usage at exit.
m_jit.addPtr(
CCallHelpers::TrustedImm32(
-m_jit.codeBlock()->jitCode()->dfgCommon()->requiredRegisterCountForExit * sizeof(Register)),
CCallHelpers::framePointerRegister, CCallHelpers::stackPointerRegister);
// 2) 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:
m_jit.sub32(recovery->src(), recovery->dest());
break;
case BooleanSpeculationCheck:
break;
default:
break;
}
}
// 3) Refine some 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).
// Note: We are free to assume that the jsValueSource is already known to
// be a cell since both BadCache and BadIndexingType exits occur after
// the cell check would have already happened.
CodeOrigin codeOrigin = exit.m_codeOriginForExitProfile;
if (ArrayProfile* arrayProfile = m_jit.baselineCodeBlockFor(codeOrigin)->getArrayProfile(codeOrigin.bytecodeIndex)) {
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();
}
GPRReg scratch1;
GPRReg scratch2;
scratch1 = AssemblyHelpers::selectScratchGPR(usedRegister1, usedRegister2);
scratch2 = AssemblyHelpers::selectScratchGPR(usedRegister1, usedRegister2, scratch1);
#if CPU(ARM64)
m_jit.pushToSave(scratch1);
m_jit.pushToSave(scratch2);
#else
m_jit.push(scratch1);
m_jit.push(scratch2);
#endif
GPRReg value;
if (exit.m_jsValueSource.isAddress()) {
value = scratch1;
m_jit.loadPtr(AssemblyHelpers::Address(exit.m_jsValueSource.asAddress()), value);
} else
value = exit.m_jsValueSource.payloadGPR();
m_jit.loadPtr(AssemblyHelpers::Address(value, JSCell::structureIDOffset()), scratch1);
m_jit.storePtr(scratch1, arrayProfile->addressOfLastSeenStructureID());
m_jit.load8(AssemblyHelpers::Address(scratch1, Structure::indexingTypeOffset()), scratch1);
m_jit.move(AssemblyHelpers::TrustedImm32(1), scratch2);
m_jit.lshift32(scratch1, scratch2);
m_jit.or32(scratch2, AssemblyHelpers::AbsoluteAddress(arrayProfile->addressOfArrayModes()));
#if CPU(ARM64)
m_jit.popToRestore(scratch2);
m_jit.popToRestore(scratch1);
#else
m_jit.pop(scratch2);
m_jit.pop(scratch1);
#endif
}
}
if (!!exit.m_valueProfile) {
EncodedJSValue* bucket = exit.m_valueProfile.getSpecFailBucket(0);
if (exit.m_jsValueSource.isAddress()) {
// Save a register so we can use it.
GPRReg scratch = AssemblyHelpers::selectScratchGPR(exit.m_jsValueSource.base());
#if CPU(ARM64)
m_jit.pushToSave(scratch);
#else
m_jit.push(scratch);
#endif
m_jit.load32(exit.m_jsValueSource.asAddress(OBJECT_OFFSETOF(EncodedValueDescriptor, asBits.tag)), scratch);
m_jit.store32(scratch, &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.tag);
m_jit.load32(exit.m_jsValueSource.asAddress(OBJECT_OFFSETOF(EncodedValueDescriptor, asBits.payload)), scratch);
m_jit.store32(scratch, &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.payload);
#if CPU(ARM64)
m_jit.popToRestore(scratch);
#else
m_jit.pop(scratch);
#endif
} else if (exit.m_jsValueSource.hasKnownTag()) {
m_jit.store32(AssemblyHelpers::TrustedImm32(exit.m_jsValueSource.tag()), &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.tag);
m_jit.store32(exit.m_jsValueSource.payloadGPR(), &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.payload);
} else {
m_jit.store32(exit.m_jsValueSource.tagGPR(), &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.tag);
m_jit.store32(exit.m_jsValueSource.payloadGPR(), &bitwise_cast<EncodedValueDescriptor*>(bucket)->asBits.payload);
}
}
}
// Do a simplified OSR exit. See DFGOSRExitCompiler64.cpp's comment regarding how and wny we
// do this simple approach.
// 4) Save all state from GPRs into the scratch buffer.
ScratchBuffer* scratchBuffer = m_jit.vm()->scratchBufferForSize(sizeof(EncodedJSValue) * operands.size());
EncodedJSValue* scratch = scratchBuffer ? static_cast<EncodedJSValue*>(scratchBuffer->dataBuffer()) : 0;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case UnboxedInt32InGPR:
case UnboxedBooleanInGPR:
case UnboxedCellInGPR:
m_jit.store32(
recovery.gpr(),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload);
break;
case InPair:
m_jit.store32(
recovery.tagGPR(),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag);
m_jit.store32(
recovery.payloadGPR(),
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload);
break;
default:
break;
}
}
// Now all GPRs are free to reuse.
// 5) 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 InFPR:
m_jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT0);
m_jit.storeDouble(recovery.fpr(), MacroAssembler::Address(GPRInfo::regT0));
break;
default:
break;
}
}
// Now all FPRs are free to reuse.
// 6) 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.
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case DisplacedInJSStack:
case Int32DisplacedInJSStack:
case DoubleDisplacedInJSStack:
case CellDisplacedInJSStack:
case BooleanDisplacedInJSStack:
m_jit.load32(
AssemblyHelpers::tagFor(recovery.virtualRegister()),
GPRInfo::regT0);
m_jit.load32(
AssemblyHelpers::payloadFor(recovery.virtualRegister()),
GPRInfo::regT1);
m_jit.store32(
GPRInfo::regT0,
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag);
m_jit.store32(
GPRInfo::regT1,
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload);
break;
default:
break;
}
}
// 7) Do all data format conversions and store the results into the stack.
bool haveArguments = false;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
int operand = operands.operandForIndex(index);
switch (recovery.technique()) {
case InPair:
case DisplacedInJSStack:
m_jit.load32(
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.tag,
GPRInfo::regT0);
m_jit.load32(
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload,
GPRInfo::regT1);
m_jit.store32(
GPRInfo::regT0,
AssemblyHelpers::tagFor(operand));
m_jit.store32(
GPRInfo::regT1,
AssemblyHelpers::payloadFor(operand));
break;
case InFPR:
case DoubleDisplacedInJSStack:
m_jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT0);
m_jit.loadDouble(GPRInfo::regT0, FPRInfo::fpRegT0);
m_jit.purifyNaN(FPRInfo::fpRegT0);
m_jit.storeDouble(FPRInfo::fpRegT0, AssemblyHelpers::addressFor(operand));
break;
case UnboxedInt32InGPR:
case Int32DisplacedInJSStack:
m_jit.load32(
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload,
GPRInfo::regT0);
m_jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::Int32Tag),
AssemblyHelpers::tagFor(operand));
m_jit.store32(
GPRInfo::regT0,
AssemblyHelpers::payloadFor(operand));
break;
case UnboxedCellInGPR:
case CellDisplacedInJSStack:
m_jit.load32(
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload,
GPRInfo::regT0);
m_jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::CellTag),
AssemblyHelpers::tagFor(operand));
m_jit.store32(
GPRInfo::regT0,
AssemblyHelpers::payloadFor(operand));
break;
case UnboxedBooleanInGPR:
case BooleanDisplacedInJSStack:
m_jit.load32(
&bitwise_cast<EncodedValueDescriptor*>(scratch + index)->asBits.payload,
GPRInfo::regT0);
m_jit.store32(
AssemblyHelpers::TrustedImm32(JSValue::BooleanTag),
AssemblyHelpers::tagFor(operand));
m_jit.store32(
GPRInfo::regT0,
AssemblyHelpers::payloadFor(operand));
break;
case Constant:
m_jit.store32(
AssemblyHelpers::TrustedImm32(recovery.constant().tag()),
AssemblyHelpers::tagFor(operand));
m_jit.store32(
AssemblyHelpers::TrustedImm32(recovery.constant().payload()),
AssemblyHelpers::payloadFor(operand));
break;
case ArgumentsThatWereNotCreated:
haveArguments = true;
m_jit.store32(
AssemblyHelpers::TrustedImm32(JSValue().tag()),
AssemblyHelpers::tagFor(operand));
m_jit.store32(
AssemblyHelpers::TrustedImm32(JSValue().payload()),
AssemblyHelpers::payloadFor(operand));
break;
default:
break;
}
}
// 8) 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(m_jit, exit);
// 9) Reify inlined call frames.
reifyInlinedCallFrames(m_jit, exit);
// 10) Create arguments if necessary and place them into the appropriate aliased
// registers.
if (haveArguments) {
ArgumentsRecoveryGenerator argumentsRecovery;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
if (recovery.technique() != ArgumentsThatWereNotCreated)
continue;
argumentsRecovery.generateFor(
operands.operandForIndex(index), exit.m_codeOrigin, m_jit);
}
}
// 12) And finish.
adjustAndJumpToTarget(m_jit, exit);
}
void OSRExitCompiler::compileExit(const OSRExit& exit, const Operands<ValueRecovery>& operands, SpeculationRecovery* recovery)
{
// 1) Pro-forma stuff.
#if DFG_ENABLE(DEBUG_VERBOSE)
dataLogF("OSR exit for (");
for (CodeOrigin codeOrigin = exit.m_codeOrigin; ; codeOrigin = codeOrigin.inlineCallFrame->caller) {
dataLogF("bc#%u", codeOrigin.bytecodeIndex);
if (!codeOrigin.inlineCallFrame)
break;
dataLogF(" -> %p ", codeOrigin.inlineCallFrame->executable.get());
}
dataLogF(") ");
dataLog(operands);
#endif
if (Options::printEachOSRExit()) {
SpeculationFailureDebugInfo* debugInfo = new SpeculationFailureDebugInfo;
debugInfo->codeBlock = m_jit.codeBlock();
m_jit.debugCall(debugOperationPrintSpeculationFailure, debugInfo);
}
#if DFG_ENABLE(JIT_BREAK_ON_SPECULATION_FAILURE)
m_jit.breakpoint();
#endif
#if DFG_ENABLE(SUCCESS_STATS)
static SamplingCounter counter("SpeculationFailure");
m_jit.emitCount(counter);
#endif
// 2) 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:
m_jit.sub32(recovery->src(), recovery->dest());
m_jit.or64(GPRInfo::tagTypeNumberRegister, recovery->dest());
break;
case BooleanSpeculationCheck:
m_jit.xor64(AssemblyHelpers::TrustedImm32(static_cast<int32_t>(ValueFalse)), recovery->dest());
break;
default:
break;
}
}
// 3) 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;
if (ArrayProfile* arrayProfile = m_jit.baselineCodeBlockFor(codeOrigin)->getArrayProfile(codeOrigin.bytecodeIndex)) {
GPRReg usedRegister;
if (exit.m_jsValueSource.isAddress())
usedRegister = exit.m_jsValueSource.base();
else
usedRegister = exit.m_jsValueSource.gpr();
GPRReg scratch1;
GPRReg scratch2;
scratch1 = AssemblyHelpers::selectScratchGPR(usedRegister);
scratch2 = AssemblyHelpers::selectScratchGPR(usedRegister, scratch1);
#if CPU(ARM64)
m_jit.pushToSave(scratch1);
m_jit.pushToSave(scratch2);
#else
m_jit.push(scratch1);
m_jit.push(scratch2);
#endif
GPRReg value;
if (exit.m_jsValueSource.isAddress()) {
value = scratch1;
m_jit.loadPtr(AssemblyHelpers::Address(exit.m_jsValueSource.asAddress()), value);
} else
value = exit.m_jsValueSource.gpr();
m_jit.loadPtr(AssemblyHelpers::Address(value, JSCell::structureOffset()), scratch1);
m_jit.storePtr(scratch1, arrayProfile->addressOfLastSeenStructure());
m_jit.load8(AssemblyHelpers::Address(scratch1, Structure::indexingTypeOffset()), scratch1);
m_jit.move(AssemblyHelpers::TrustedImm32(1), scratch2);
m_jit.lshift32(scratch1, scratch2);
m_jit.or32(scratch2, AssemblyHelpers::AbsoluteAddress(arrayProfile->addressOfArrayModes()));
#if CPU(ARM64)
m_jit.popToRestore(scratch2);
m_jit.popToRestore(scratch1);
#else
m_jit.pop(scratch2);
m_jit.pop(scratch1);
#endif
}
}
if (!!exit.m_valueProfile) {
EncodedJSValue* bucket = exit.m_valueProfile.getSpecFailBucket(0);
if (exit.m_jsValueSource.isAddress()) {
// We can't be sure that we have a spare register. So use the tagTypeNumberRegister,
// since we know how to restore it.
m_jit.load64(AssemblyHelpers::Address(exit.m_jsValueSource.asAddress()), GPRInfo::tagTypeNumberRegister);
m_jit.store64(GPRInfo::tagTypeNumberRegister, bucket);
m_jit.move(AssemblyHelpers::TrustedImm64(TagTypeNumber), GPRInfo::tagTypeNumberRegister);
} else
m_jit.store64(exit.m_jsValueSource.gpr(), bucket);
}
}
// 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.
// 4) Save all state from GPRs into the scratch buffer.
ScratchBuffer* scratchBuffer = m_jit.vm()->scratchBufferForSize(sizeof(EncodedJSValue) * operands.size());
EncodedJSValue* scratch = scratchBuffer ? static_cast<EncodedJSValue*>(scratchBuffer->dataBuffer()) : 0;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case InGPR:
case UnboxedInt32InGPR:
case UInt32InGPR:
case UnboxedInt52InGPR:
case UnboxedStrictInt52InGPR:
case UnboxedCellInGPR:
m_jit.store64(recovery.gpr(), scratch + index);
break;
default:
break;
}
}
// And voila, all GPRs are free to reuse.
// 5) 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 InFPR:
m_jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT0);
m_jit.storeDouble(recovery.fpr(), GPRInfo::regT0);
break;
default:
break;
}
}
// Now, all FPRs are also free.
// 6) 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.
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
switch (recovery.technique()) {
case DisplacedInJSStack:
case CellDisplacedInJSStack:
case BooleanDisplacedInJSStack:
case Int32DisplacedInJSStack:
case DoubleDisplacedInJSStack:
case Int52DisplacedInJSStack:
case StrictInt52DisplacedInJSStack:
m_jit.load64(AssemblyHelpers::addressFor(recovery.virtualRegister()), GPRInfo::regT0);
m_jit.store64(GPRInfo::regT0, scratch + index);
break;
default:
break;
}
}
// 7) Do all data format conversions and store the results into the stack.
bool haveArguments = false;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
int operand = operands.operandForIndex(index);
switch (recovery.technique()) {
case InGPR:
case UnboxedCellInGPR:
case DisplacedInJSStack:
case CellDisplacedInJSStack:
case BooleanDisplacedInJSStack:
m_jit.load64(scratch + index, GPRInfo::regT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case UnboxedInt32InGPR:
case Int32DisplacedInJSStack:
m_jit.load64(scratch + index, GPRInfo::regT0);
m_jit.zeroExtend32ToPtr(GPRInfo::regT0, GPRInfo::regT0);
m_jit.or64(GPRInfo::tagTypeNumberRegister, GPRInfo::regT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case UnboxedInt52InGPR:
case Int52DisplacedInJSStack:
m_jit.load64(scratch + index, GPRInfo::regT0);
m_jit.rshift64(
AssemblyHelpers::TrustedImm32(JSValue::int52ShiftAmount), GPRInfo::regT0);
m_jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case UnboxedStrictInt52InGPR:
case StrictInt52DisplacedInJSStack:
m_jit.load64(scratch + index, GPRInfo::regT0);
m_jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case UInt32InGPR:
m_jit.load64(scratch + index, GPRInfo::regT0);
m_jit.zeroExtend32ToPtr(GPRInfo::regT0, GPRInfo::regT0);
m_jit.boxInt52(GPRInfo::regT0, GPRInfo::regT0, GPRInfo::regT1, FPRInfo::fpRegT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case InFPR:
case DoubleDisplacedInJSStack:
m_jit.move(AssemblyHelpers::TrustedImmPtr(scratch + index), GPRInfo::regT0);
m_jit.loadDouble(GPRInfo::regT0, FPRInfo::fpRegT0);
m_jit.boxDouble(FPRInfo::fpRegT0, GPRInfo::regT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
break;
case Constant:
m_jit.store64(
AssemblyHelpers::TrustedImm64(JSValue::encode(recovery.constant())),
AssemblyHelpers::addressFor(operand));
break;
case ArgumentsThatWereNotCreated:
haveArguments = true;
// We can't restore this yet but we can make sure that the stack appears
// sane.
m_jit.store64(
AssemblyHelpers::TrustedImm64(JSValue::encode(JSValue())),
AssemblyHelpers::addressFor(operand));
break;
default:
break;
}
}
// 8) 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(m_jit, exit);
// 9) Reify inlined call frames.
reifyInlinedCallFrames(m_jit, exit);
// 10) Create arguments if necessary and place them into the appropriate aliased
// registers.
if (haveArguments) {
HashSet<InlineCallFrame*, DefaultHash<InlineCallFrame*>::Hash,
NullableHashTraits<InlineCallFrame*> > didCreateArgumentsObject;
for (size_t index = 0; index < operands.size(); ++index) {
const ValueRecovery& recovery = operands[index];
if (recovery.technique() != ArgumentsThatWereNotCreated)
continue;
int operand = operands.operandForIndex(index);
// Find the right inline call frame.
InlineCallFrame* inlineCallFrame = 0;
for (InlineCallFrame* current = exit.m_codeOrigin.inlineCallFrame;
current;
current = current->caller.inlineCallFrame) {
if (current->stackOffset >= operand) {
inlineCallFrame = current;
break;
}
}
if (!m_jit.baselineCodeBlockFor(inlineCallFrame)->usesArguments())
continue;
VirtualRegister argumentsRegister = m_jit.baselineArgumentsRegisterFor(inlineCallFrame);
if (didCreateArgumentsObject.add(inlineCallFrame).isNewEntry) {
// We know this call frame optimized out an arguments object that
// the baseline JIT would have created. Do that creation now.
if (inlineCallFrame) {
m_jit.addPtr(AssemblyHelpers::TrustedImm32(inlineCallFrame->stackOffset * sizeof(EncodedJSValue)), GPRInfo::callFrameRegister, GPRInfo::regT0);
m_jit.setupArguments(GPRInfo::regT0);
} else
m_jit.setupArgumentsExecState();
m_jit.move(
AssemblyHelpers::TrustedImmPtr(
bitwise_cast<void*>(operationCreateArguments)),
GPRInfo::nonArgGPR0);
m_jit.call(GPRInfo::nonArgGPR0);
m_jit.store64(GPRInfo::returnValueGPR, AssemblyHelpers::addressFor(argumentsRegister));
m_jit.store64(
GPRInfo::returnValueGPR,
AssemblyHelpers::addressFor(unmodifiedArgumentsRegister(argumentsRegister)));
m_jit.move(GPRInfo::returnValueGPR, GPRInfo::regT0); // no-op move on almost all platforms.
}
m_jit.load64(AssemblyHelpers::addressFor(argumentsRegister), GPRInfo::regT0);
m_jit.store64(GPRInfo::regT0, AssemblyHelpers::addressFor(operand));
}
}
// 11) Load the result of the last bytecode operation into regT0.
if (exit.m_lastSetOperand.isValid())
m_jit.load64(AssemblyHelpers::addressFor(exit.m_lastSetOperand), GPRInfo::cachedResultRegister);
// 12) And finish.
adjustAndJumpToTarget(m_jit, exit);
}
