void JITCompiler::exceptionCheck()
{
// It's important that we use origin.forExit here. Consider if we hoist string
// addition outside a loop, and that we exit at the point of that concatenation
// from an out of memory exception.
// If the original loop had a try/catch around string concatenation, if we "catch"
// that exception inside the loop, then the loops induction variable will be undefined
// in the OSR exit value recovery. It's more defensible for the string concatenation,
// then, to not be caught by the for loops' try/catch.
// Here is the program I'm speaking about:
//
// >>>> lets presume "c = a + b" gets hoisted here.
// for (var i = 0; i < length; i++) {
// try {
// c = a + b
// } catch(e) {
// If we threw an out of memory error, and we cought the exception
// right here, then "i" would almost certainly be undefined, which
// would make no sense.
// ...
// }
// }
CodeOrigin opCatchOrigin;
HandlerInfo* exceptionHandler;
bool willCatchException = m_graph.willCatchExceptionInMachineFrame(m_speculative->m_currentNode->origin.forExit, opCatchOrigin, exceptionHandler);
if (willCatchException) {
unsigned streamIndex = m_speculative->m_outOfLineStreamIndex != UINT_MAX ? m_speculative->m_outOfLineStreamIndex : m_speculative->m_stream->size();
MacroAssembler::Jump hadException = emitNonPatchableExceptionCheck();
// We assume here that this is called after callOpeartion()/appendCall() is called.
appendExceptionHandlingOSRExit(ExceptionCheck, streamIndex, opCatchOrigin, exceptionHandler, m_jitCode->common.lastCallSite(), hadException);
} else
m_exceptionChecks.append(emitExceptionCheck());
}
void JIT::compileCallEval(Instruction* instruction)
{
addPtr(TrustedImm32(-static_cast<ptrdiff_t>(sizeof(CallerFrameAndPC))), stackPointerRegister, regT1);
callOperationNoExceptionCheck(operationCallEval, regT1);
Jump noException = emitExceptionCheck(InvertedExceptionCheck);
addPtr(TrustedImm32(stackPointerOffsetFor(m_codeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);
exceptionCheck(jump());
noException.link(this);
addSlowCase(branch64(Equal, regT0, TrustedImm64(JSValue::encode(JSValue()))));
addPtr(TrustedImm32(stackPointerOffsetFor(m_codeBlock) * sizeof(Register)), callFrameRegister, stackPointerRegister);
checkStackPointerAlignment();
sampleCodeBlock(m_codeBlock);
emitPutCallResult(instruction);
}
