[llvm] [InstCombine] Handle IsInf/IsZero idioms (PR #80607)

[Matt Arsenault via llvm-commits]

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@@ -200,4 +312,44 @@ define i1 @f32_fcnan_fcinf_noimplicitfloat(float %a) #0 {
   ret i1 %cmp
 }
 
+define i1 @f32_fcposinf_noimplicitfloat(float %a) #0 {
+; CHECK-LABEL: define i1 @f32_fcposinf_noimplicitfloat(
+; CHECK-SAME: float [[A:%.*]]) #[[ATTR1]] {
+; CHECK-NEXT:    [[I32:%.*]] = bitcast float [[A]] to i32
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I32]], 2139095040
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %i32 = bitcast float %a to i32
+  %cmp = icmp eq i32 %i32, 2139095040
+  ret i1 %cmp
+}
+
+define i1 @f32_fcposnan(float %a) {
+; CHECK-LABEL: define i1 @f32_fcposnan(
+; CHECK-SAME: float [[A:%.*]]) {
+; CHECK-NEXT:    [[I32:%.*]] = bitcast float [[A]] to i32
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I32]], 2139095041
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %i32 = bitcast float %a to i32
+  %cmp = icmp eq i32 %i32, 2139095041
+  ret i1 %cmp
+}
+
+define i1 @f32_fcposinf_multiuse(float %a) {
+; CHECK-LABEL: define i1 @f32_fcposinf_multiuse(
+; CHECK-SAME: float [[A:%.*]]) {
+; CHECK-NEXT:    [[I32:%.*]] = bitcast float [[A]] to i32
+; CHECK-NEXT:    call void @usei32(i32 [[I32]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I32]], 2139095040
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %i32 = bitcast float %a to i32
+  call void @usei32(i32 %i32)
+  %cmp = icmp eq i32 %i32, 2139095040
+  ret i1 %cmp
+}
+
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arsenm wrote:

This doesn't include the fpext/fptrunc cases 

https://github.com/llvm/llvm-project/pull/80607