diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 28 |
1 files changed, 14 insertions, 14 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index f87b94dd355..2b9db4baafa 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -1417,21 +1417,21 @@ Instruction *InstCombiner::foldShuffledBinop(BinaryOperator &Inst) { } } if (MayChange) { - // It's not safe to use a vector with undef elements because the entire - // instruction can be folded to undef (for example, div/rem divisors). - // Replace undef lanes with the first non-undef element. Vector demanded - // elements can change those back to undef values if that is safe. - Constant *SafeDummyConstant = nullptr; - for (unsigned i = 0; i < VWidth; ++i) { - if (!isa<UndefValue>(NewVecC[i])) { - SafeDummyConstant = NewVecC[i]; - break; - } + // With integer div/rem instructions, it is not safe to use a vector with + // undef elements because the entire instruction can be folded to undef. + // So replace undef elements with '1' because that can never induce + // undefined behavior. All other binop opcodes are always safe to + // speculate, and therefore, it is fine to include undef elements for + // unused lanes (and using undefs may help optimization). + BinaryOperator::BinaryOps Opcode = Inst.getOpcode(); + if (Opcode == Instruction::UDiv || Opcode == Instruction::URem || + Opcode == Instruction::SDiv || Opcode == Instruction::SRem) { + assert(C->getType()->getScalarType()->isIntegerTy() && + "Not expecting FP opcodes/operands/constants here"); + for (unsigned i = 0; i < VWidth; ++i) + if (isa<UndefValue>(NewVecC[i])) + NewVecC[i] = ConstantInt::get(NewVecC[i]->getType(), 1); } - assert(SafeDummyConstant && "Undef constant vector was not simplified?"); - for (unsigned i = 0; i < VWidth; ++i) - if (isa<UndefValue>(NewVecC[i])) - NewVecC[i] = SafeDummyConstant; // Op(shuffle(V1, Mask), C) -> shuffle(Op(V1, NewC), Mask) // Op(C, shuffle(V1, Mask)) -> shuffle(Op(NewC, V1), Mask) |
