SSATmp* TraceBuilder::preOptimizeDecRefThis(IRInstruction* inst) {
/*
* If $this is available, convert to an instruction sequence that
* doesn't need to test if it's already live.
*/
if (isThisAvailable()) {
auto const thiss = gen(LdThis, m_fpValue);
auto const thisInst = thiss->inst();
/*
* DecRef optimization for $this in an inlined frame: if a caller
* local contains the $this, we know it can't go to zero and can
* switch DecRef to DecRefNZ.
*
* It's ok not to do DecRefThis (which normally nulls out the ActRec
* $this), because there is still a reference to it in the caller
* frame, so debug_backtrace() can't see a non-live pointer value.
*/
if (thisInst->op() == IncRef &&
callerHasValueAvailable(thisInst->src(0))) {
gen(DecRefNZ, thiss);
inst->convertToNop();
return nullptr;
}
assert(inst->src(0) == m_fpValue);
gen(DecRef, thiss);
inst->convertToNop();
return nullptr;
}
return nullptr;
}
SSATmp* TraceBuilder::preOptimizeLdThis(IRInstruction* inst) {
if (isThisAvailable()) {
auto fpInst = inst->src(0)->inst();
if (fpInst->op() == DefInlineFP) {
if (!m_frameSpansCall) { // check that we haven't nuked the SSATmp
auto spInst = fpInst->src(0)->inst();
if (spInst->op() == SpillFrame && spInst->src(3)->isA(Type::Obj)) {
return spInst->src(3);
}
}
}
inst->setTaken(nullptr);
}
return nullptr;
}
SSATmp* TraceBuilder::preOptimizeLdCtx(IRInstruction* inst) {
if (isThisAvailable()) return gen(LdThis, m_fpValue);
return nullptr;
}
SSATmp* TraceBuilder::preOptimizeLdThis(IRInstruction* inst) {
if (isThisAvailable()) inst->setTaken(nullptr);
return nullptr;
}
