diff options
Diffstat (limited to 'llvm/lib/CodeGen/CodeGenPrepare.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/CodeGenPrepare.cpp | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp index d100038..9ed4f5b 100644 --- a/llvm/lib/CodeGen/CodeGenPrepare.cpp +++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp @@ -7048,12 +7048,29 @@ bool CodeGenPrepare::optimizeSwitchPhiConstants(SwitchInst *SI) { bool CheckedForSinglePred = false; for (PHINode &PHI : CaseBB->phis()) { Type *PHIType = PHI.getType(); - if (PHIType == ConditionType) { + // If ZExt is free then we can also catch patterns like this: + // switch((i32)x) { case 42: phi((i64)42, ...); } + // and replace `(i64)42` with `zext i32 %x to i64`. + bool TryZExt = + PHIType->isIntegerTy() && + PHIType->getIntegerBitWidth() > ConditionType->getIntegerBitWidth() && + TLI->isZExtFree(ConditionType, PHIType); + if (PHIType == ConditionType || TryZExt) { // Set to true to skip this case because of multiple preds. bool SkipCase = false; + Value *Replacement = nullptr; for (unsigned I = 0, E = PHI.getNumIncomingValues(); I != E; I++) { - if (PHI.getIncomingValue(I) != CaseValue || - PHI.getIncomingBlock(I) != SwitchBB) + Value *PHIValue = PHI.getIncomingValue(I); + if (PHIValue != CaseValue) { + if (!TryZExt) + continue; + ConstantInt *PHIValueInt = dyn_cast<ConstantInt>(PHIValue); + if (!PHIValueInt || + PHIValueInt->getValue() != + CaseValue->getValue().zext(PHIType->getIntegerBitWidth())) + continue; + } + if (PHI.getIncomingBlock(I) != SwitchBB) continue; // We cannot optimize if there are multiple case labels jumping to // this block. This check may get expensive when there are many @@ -7066,7 +7083,15 @@ bool CodeGenPrepare::optimizeSwitchPhiConstants(SwitchInst *SI) { } } - PHI.setIncomingValue(I, Condition); + if (Replacement == nullptr) { + if (PHIValue == CaseValue) { + Replacement = Condition; + } else { + IRBuilder<> Builder(SI); + Replacement = Builder.CreateZExt(Condition, PHIType); + } + } + PHI.setIncomingValue(I, Replacement); Changed = true; } if (SkipCase) |