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[InstCombine] Ensure all undef operands are handled before binary instruction constant folding

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As noted in PR18355, this patch makes it clear that all cases with undef operands have been handled before further constant folding is attempted.

Differential Revision: http://reviews.llvm.org/D18305

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263994 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Simon Pilgrim 2016-03-21 22:15:50 +00:00
parent 814be6ba00
commit 752e5f9178
1 changed files with 16 additions and 2 deletions
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18
lib/IR/ConstantFold.cpp
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@ -916,9 +916,11 @@ Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
Constant *C1, Constant *C2) {
assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
// Handle UndefValue up front.
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
switch (Opcode) {
switch (static_cast<Instruction::BinaryOps>(Opcode)) {
case Instruction::Xor:
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
// Handle undef ^ undef -> 0 special case. This is a common
@ -998,9 +1000,22 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
return C1;
// undef << X -> 0
return Constant::getNullValue(C1->getType());
case Instruction::FAdd:
case Instruction::FSub:
case Instruction::FMul:
case Instruction::FDiv:
case Instruction::FRem:
// TODO: UNDEF handling for binary float instructions.
return nullptr;
case Instruction::BinaryOpsEnd:
llvm_unreachable("Invalid BinaryOp");
}
}
// At this point neither constant should be an UndefValue.
assert(!isa<UndefValue>(C1) && !isa<UndefValue>(C2) &&
"Unexpected UndefValue");
// Handle simplifications when the RHS is a constant int.
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
switch (Opcode) {
@ -1102,7 +1117,6 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
return ConstantExpr::get(Opcode, C2, C1);
}
// At this point we know neither constant is an UndefValue.
if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) {
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
const APInt &C1V = CI1->getValue();