[InstSimplify] fsub 0.0, (fsub -0.0, X) ==> X is only safe if signed zeros are ignored.

Only allow fsub -0.0, (fsub -0.0, X) ==> X without nsz. PR26746.

llvm-svn: 262212

1 files changed, 23 insertions, 3 deletions

diff --git a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
index b0957a81773..1c29884753a 100644
--- a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
+++ b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
@@ -1,8 +1,8 @@
 ; RUN: opt < %s -instsimplify -S | FileCheck %s
 
-; fsub 0, (fsub 0, X) ==> X
-; CHECK-LABEL: @fsub_0_0_x(
-define float @fsub_0_0_x(float %a) {
+; fsub -0.0, (fsub -0.0, X) ==> X
+; CHECK-LABEL: @fsub_-0_-0_x(
+define float @fsub_-0_-0_x(float %a) {
   %t1 = fsub float -0.0, %a
   %ret = fsub float -0.0, %t1
 
@@ -10,6 +10,26 @@ define float @fsub_0_0_x(float %a) {
   ret float %ret
 }
 
+; fsub 0.0, (fsub -0.0, X) != X
+; CHECK-LABEL: @fsub_0_-0_x(
+define float @fsub_0_-0_x(float %a) {
+  %t1 = fsub float 0.0, %a
+  %ret = fsub float -0.0, %t1
+
+; CHECK-NOT: ret float %a
+  ret float %ret
+}
+
+; fsub -0.0, (fsub 0.0, X) != X
+; CHECK-LABEL: @fsub_-0_0_x(
+define float @fsub_-0_0_x(float %a) {
+  %t1 = fsub float -0.0, %a
+  %ret = fsub float 0.0, %t1
+
+; CHECK-NOT: ret float %a
+  ret float %ret
+}
+
 ; fsub X, 0 ==> X
 ; CHECK-LABEL: @fsub_x_0(
 define float @fsub_x_0(float %a) {