Only have codegen turn fdiv by a constant into fmul by the reciprocal
when -ffast-math, i.e. don't just always do it if the reciprocal can
be formed exactly. There is already an IR level transform that does
that, and it does it more carefully.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154296 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ebffb85..f1b9f43 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5725,16 +5725,14 @@
if (N0CFP && N1CFP && VT != MVT::ppcf128)
return DAG.getNode(ISD::FDIV, N->getDebugLoc(), VT, N0, N1);
- // fold (fdiv X, c2) -> fmul X, 1/c2 if there is no precision loss or if
- // losing precision is acceptable.
- if (N1CFP && VT != MVT::ppcf128) {
+ // fold (fdiv X, c2) -> fmul X, 1/c2 if losing precision is acceptable.
+ if (N1CFP && VT != MVT::ppcf128 && DAG.getTarget().Options.UnsafeFPMath) {
// Compute the reciprocal 1.0 / c2.
APFloat N1APF = N1CFP->getValueAPF();
APFloat Recip(N1APF.getSemantics(), 1); // 1.0
APFloat::opStatus st = Recip.divide(N1APF, APFloat::rmNearestTiesToEven);
// Only do the transform if the reciprocal is not too horrible (eg not NaN).
- if (st == APFloat::opOK || (st == APFloat::opInexact &&
- DAG.getTarget().Options.UnsafeFPMath))
+ if (st == APFloat::opOK || st == APFloat::opInexact)
return DAG.getNode(ISD::FMUL, N->getDebugLoc(), VT, N0,
DAG.getConstantFP(Recip, VT));
}