Fix an instance where we would drop fast math flags when performing an fdiv to reciprocal multiply transformation.

llvm-svn: 199425

2 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 94461c5f84a..f61d82340b5 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1050,8 +1050,10 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
     }
 
     // X / C => X * 1/C
-    if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal))
+    if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) {
+      T->copyFastMathFlags(&I);
       return T;
+    }
 
     return 0;
   }
diff --git a/llvm/test/Transforms/InstCombine/fdiv.ll b/llvm/test/Transforms/InstCombine/fdiv.ll
index 1edbc5ecd60..c3aabd78666 100644
--- a/llvm/test/Transforms/InstCombine/fdiv.ll
+++ b/llvm/test/Transforms/InstCombine/fdiv.ll
@@ -23,3 +23,11 @@ define float @test3(float %x) nounwind readnone ssp {
 ; CHECK-LABEL: @test3(
 ; CHECK-NEXT: fdiv float %x, 0x36A0000000000000
 }
+
+define float @test4(float %x) nounwind readnone ssp {
+  %div = fdiv fast float %x, 8.0
+  ret float %div
+
+; CHECK-LABEL: @test4(
+; CHECK-NEXT: fmul fast float %x, 1.250000e-01
+}