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Fix for http://llvm.org/bugs/show_bug.cgi?id=18590

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This patch fixes the bug in peephole optimization that folds a load which defines one vreg into the one and only use of that vreg. With debug info, a DBG_VALUE that referenced the vreg considered to be a use, preventing the optimization. The fix is to ignore DBG_VALUE's during the optimization, and undef a DBG_VALUE that references a vreg that gets removed.
Patch by Trevor Smigiel!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203829 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ekaterina Romanova
2014-03-13 18:47:12 +00:00
parent 4ad41871eb
commit ed2ca70ccf
5 changed files with 114 additions and 14 deletions
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14
lib/CodeGen/PeepholeOptimizer.cpp
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@ -505,12 +505,12 @@ bool PeepholeOptimizer::isLoadFoldable(MachineInstr *MI,
return false;
unsigned Reg = MI->getOperand(0).getReg();
// To reduce compilation time, we check MRI->hasOneUse when inserting
// To reduce compilation time, we check MRI->hasOneNonDBGUse when inserting
// loads. It should be checked when processing uses of the load, since
// uses can be removed during peephole.
if (!MI->getOperand(0).getSubReg() &&
TargetRegisterInfo::isVirtualRegister(Reg) &&
MRI->hasOneUse(Reg)) {
MRI->hasOneNonDBGUse(Reg)) {
FoldAsLoadDefReg = Reg;
return true;
}
@ -594,10 +594,14 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
++MII;
LocalMIs.insert(MI);
// Skip debug values. They should not affect this peephole optimization.
if (MI->isDebugValue())
continue;
// If there exists an instruction which belongs to the following
// categories, we will discard the load candidate.
if (MI->isPosition() || MI->isPHI() || MI->isImplicitDef() ||
MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
MI->isKill() || MI->isInlineAsm() ||
MI->hasUnmodeledSideEffects()) {
FoldAsLoadDefReg = 0;
continue;
@ -633,6 +637,9 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
if (!isLoadFoldable(MI, FoldAsLoadDefReg) && FoldAsLoadDefReg) {
// We need to fold load after optimizeCmpInstr, since optimizeCmpInstr
// can enable folding by converting SUB to CMP.
// Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and we
// need it for markUsesInDebugValueAsUndef().
unsigned FoldedReg = FoldAsLoadDefReg;
MachineInstr *DefMI = 0;
MachineInstr *FoldMI = TII->optimizeLoadInstr(MI, MRI,
FoldAsLoadDefReg, DefMI);
@ -645,6 +652,7 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
LocalMIs.insert(FoldMI);
MI->eraseFromParent();
DefMI->eraseFromParent();
MRI->markUsesInDebugValueAsUndef(FoldedReg);
++NumLoadFold;
// MI is replaced with FoldMI.