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[InstCombine] add FMF guard to builder in fptrunc transform; NFC 

This makes no difference currently because we don't apply FMF
to FP casts, but that may change.

This could also be a place to add a fold for select with fptrunc,
so it will make that patch easier/smaller.
This commit is contained in:
Sanjay Patel 2019-12-05 10:50:43 -05:00
parent 30e8f80fd5
commit 51e420c27e
1 changed files with 5 additions and 0 deletions
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5
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
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@ -1622,6 +1622,11 @@ Instruction *InstCombiner::visitFPTrunc(FPTruncInst &FPT) {
Value *X;
Instruction *Op = dyn_cast<Instruction>(FPT.getOperand(0));
if (Op && Op->hasOneUse()) {
// FIXME: The FMF should propagate from the fptrunc, not the source op.
IRBuilder<>::FastMathFlagGuard FMFG(Builder);
if (isa<FPMathOperator>(Op))
Builder.setFastMathFlags(Op->getFastMathFlags());
if (match(Op, m_FNeg(m_Value(X)))) {
Value *InnerTrunc = Builder.CreateFPTrunc(X, Ty);