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[ARM][RDA] Allow multiple killed users 

In RDA, check against the already decided dead instructions when
looking at users. This allows an instruction to be removed if it
has multiple users, but they're all dead.

This means that IT instructions can be considered killed once all
the itstate using instructions are dead.

Differential Revision: https://reviews.llvm.org/D75245
This commit is contained in:
Sam Parker 2020-02-27 10:54:08 +00:00
parent f9896435c9
commit dfe8f5da4c
2 changed files with 5 additions and 5 deletions
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7
llvm/lib/CodeGen/ReachingDefAnalysis.cpp
View File

@ -547,7 +547,7 @@ ReachingDefAnalysis::isSafeToRemove(MachineInstr *MI, InstSet &Visited,
void ReachingDefAnalysis::collectLocalKilledOperands(MachineInstr *MI, void ReachingDefAnalysis::collectLocalKilledOperands(MachineInstr *MI,
InstSet &Dead) const { InstSet &Dead) const {
Dead.insert(MI); Dead.insert(MI);
auto IsDead = [this](MachineInstr *Def, int PhysReg) { auto IsDead = [this, &Dead](MachineInstr *Def, int PhysReg) {
unsigned LiveDefs = 0; unsigned LiveDefs = 0;
for (auto &MO : Def->operands()) { for (auto &MO : Def->operands()) {
if (!isValidRegDef(MO)) if (!isValidRegDef(MO))
@ -561,7 +561,10 @@ void ReachingDefAnalysis::collectLocalKilledOperands(MachineInstr *MI,
SmallPtrSet<MachineInstr*, 4> Uses; SmallPtrSet<MachineInstr*, 4> Uses;
getGlobalUses(Def, PhysReg, Uses); getGlobalUses(Def, PhysReg, Uses);
return Uses.size() == 1; for (auto *Use : Uses)
if (!Dead.count(Use))
return false;
return true;
}; };
for (auto &MO : MI->operands()) { for (auto &MO : MI->operands()) {

3
llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
View File

@ -943,11 +943,8 @@ void ARMLowOverheadLoops::IterationCountDCE(LowOverheadLoop &LoLoop) {
if (ModifiedITs.empty()) { if (ModifiedITs.empty()) {
LLVM_DEBUG(dbgs() << "ARM Loops: Will remove iteration count:\n"; LLVM_DEBUG(dbgs() << "ARM Loops: Will remove iteration count:\n";
for (auto *MI : Killed) for (auto *MI : Killed)
dbgs() << " - " << *MI;
for (auto *MI : DeadITs)
dbgs() << " - " << *MI); dbgs() << " - " << *MI);
LoLoop.ToRemove.insert(Killed.begin(), Killed.end()); LoLoop.ToRemove.insert(Killed.begin(), Killed.end());
LoLoop.ToRemove.insert(DeadITs.begin(), DeadITs.end());
} }
// Collect and remove the users of iteration count. // Collect and remove the users of iteration count.