[llvm] [InstCombine] Fix FMF propagation in `copysign Mag, (copysign ?, X) -> copysign Mag, X` (PR #121574)

[Matt Arsenault via llvm-commits]

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@@ -82,14 +82,24 @@ define float @not_known_positive_sign_arg(float %x, float %y) {
 
 define float @copysign_sign_arg(float %x, float %y, float %z) {
 ; CHECK-LABEL: @copysign_sign_arg(
-; CHECK-NEXT:    [[R:%.*]] = call ninf float @llvm.copysign.f32(float [[X:%.*]], float [[Z:%.*]])
+; CHECK-NEXT:    [[R:%.*]] = call float @llvm.copysign.f32(float [[X:%.*]], float [[Z:%.*]])
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %s = call reassoc float @llvm.copysign.f32(float %y, float %z)
   %r = call ninf float @llvm.copysign.f32(float %x, float %s)
   ret float %r
 }
 
+define float @copysign_sign_arg_nnan(float %x, float %y, float %z) {
+; CHECK-LABEL: @copysign_sign_arg_nnan(
+; CHECK-NEXT:    [[R:%.*]] = call nnan float @llvm.copysign.f32(float [[X:%.*]], float [[Z:%.*]])
+; CHECK-NEXT:    ret float [[R]]
+;
+  %s = call nnan float @llvm.copysign.f32(float %y, float %z)
+  %r = call nnan float @llvm.copysign.f32(float %x, float %s)
+  ret float %r
+}
+
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arsenm wrote:

nsz is probably fine as an or but that's maybe overcomplicating it 

https://github.com/llvm/llvm-project/pull/121574