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In the below scenario, we must be able to skip the a DBG_VALUE instruction and

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remove the dead store.

%vreg0<def> = L2_loadri_io <fi#15>, 0; mem:LD4[%dataF](align=4)
DBG_VALUE %vreg0, %noreg, !"dataF", <!184>; IntRegs:%vreg0 
S2_storeri_io <fi#15>, 0, %vreg0; mem:ST4[%dataF]

In reality, this kind of stores are eliminated before Stack Slot Coloring pass,
possibly in instruction lowering

Differential Revision: https://reviews.llvm.org/D26616

llvm-svn: 291455
This commit is contained in:
Sumanth Gundapaneni 2017-01-09 17:45:02 +00:00
parent 3f38e64dde
commit c5b243c780
1 changed files with 8 additions and 3 deletions
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11
lib/CodeGen/StackSlotColoring.cpp
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@ -381,7 +381,6 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
I != E; ++I) {
if (DCELimit != -1 && (int)NumDead >= DCELimit)
break;
int FirstSS, SecondSS;
if (TII->isStackSlotCopy(*I, FirstSS, SecondSS) && FirstSS == SecondSS &&
FirstSS != -1) {
@ -392,12 +391,18 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
}
MachineBasicBlock::iterator NextMI = std::next(I);
if (NextMI == MBB->end()) continue;
MachineBasicBlock::iterator ProbableLoadMI = I;
unsigned LoadReg = 0;
unsigned StoreReg = 0;
if (!(LoadReg = TII->isLoadFromStackSlot(*I, FirstSS)))
continue;
// Skip the ...pseudo debugging... instructions between a load and store.
while ((NextMI != E) && NextMI->isDebugValue()) {
++NextMI;
++I;
}
if (NextMI == E) continue;
if (!(StoreReg = TII->isStoreToStackSlot(*NextMI, SecondSS)))
continue;
if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1) continue;
@ -407,7 +412,7 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
if (NextMI->findRegisterUseOperandIdx(LoadReg, true, nullptr) != -1) {
++NumDead;
toErase.push_back(&*I);
toErase.push_back(&*ProbableLoadMI);
}
toErase.push_back(&*NextMI);