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.

llvm-svn: 154296

1 files changed, 3 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index ebffb8562ef..f1b9f4385e4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5725,16 +5725,14 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
   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));
   }