diff options
Diffstat (limited to 'lib/VMCore/ConstantFold.cpp')
| -rw-r--r-- | lib/VMCore/ConstantFold.cpp | 37 |
1 files changed, 31 insertions, 6 deletions
diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp index 579d356..b7a1350 100644 --- a/lib/VMCore/ConstantFold.cpp +++ b/lib/VMCore/ConstantFold.cpp @@ -730,9 +730,12 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, } + if (isa<UndefValue>(Cond)) { + if (isa<UndefValue>(V1)) return V1; + return V2; + } if (isa<UndefValue>(V1)) return V2; if (isa<UndefValue>(V2)) return V1; - if (isa<UndefValue>(Cond)) return V1; if (V1 == V2) return V1; if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { @@ -1014,20 +1017,38 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, case Instruction::Add: case Instruction::Sub: return UndefValue::get(C1->getType()); - case Instruction::Mul: case Instruction::And: + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef + return C1; + return Constant::getNullValue(C1->getType()); // undef & X -> 0 + case Instruction::Mul: { + ConstantInt *CI; + // X * undef -> undef if X is odd or undef + if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) || + ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) || + (isa<UndefValue>(C1) && isa<UndefValue>(C2))) + return UndefValue::get(C1->getType()); + + // X * undef -> 0 otherwise return Constant::getNullValue(C1->getType()); + } case Instruction::UDiv: case Instruction::SDiv: + // undef / 1 -> undef + if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) + if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) + if (CI2->isOne()) + return C1; + // FALL THROUGH case Instruction::URem: case Instruction::SRem: if (!isa<UndefValue>(C2)) // undef / X -> 0 return Constant::getNullValue(C1->getType()); return C2; // X / undef -> undef case Instruction::Or: // X | undef -> -1 - if (const VectorType *PTy = dyn_cast<VectorType>(C1->getType())) - return Constant::getAllOnesValue(PTy); - return Constant::getAllOnesValue(C1->getType()); + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef + return C1; + return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 case Instruction::LShr: if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) return C1; // undef lshr undef -> undef @@ -1041,6 +1062,8 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, else return C1; // X ashr undef --> X case Instruction::Shl: + if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) + return C1; // undef shl undef -> undef // undef << X -> 0 or X << undef -> 0 return Constant::getNullValue(C1->getType()); } @@ -1831,7 +1854,9 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { // For EQ and NE, we can always pick a value for the undef to make the // predicate pass or fail, so we can return undef. - if (ICmpInst::isEquality(ICmpInst::Predicate(pred))) + // Also, if both operands are undef, we can return undef. + if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) || + (isa<UndefValue>(C1) && isa<UndefValue>(C2))) return UndefValue::get(ResultTy); // Otherwise, pick the same value as the non-undef operand, and fold // it to true or false. |