[llvm] [SimplifyLibCalls] fdim constant fold (PR #109235)

[via llvm-commits]

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@@ -0,0 +1,89 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define double @fdim_double() {
+; CHECK-LABEL: define double @fdim_double() {
+; CHECK-NEXT:    ret double 2.500000e+00
+;
+  %dim = call double @fdim(double 10.5, double 8.0)
+  ret double %dim
+}
+
+define double @fdim_double1() {
+; CHECK-LABEL: define double @fdim_double1() {
+; CHECK-NEXT:    ret double 0.000000e+00
+;
+  %dim = call double @fdim(double 7.0, double 8.0)
+  ret double %dim
+}
+
+define float @fdim_float() {
+; CHECK-LABEL: define float @fdim_float() {
+; CHECK-NEXT:    ret float 0.000000e+00
+;
+  %dim = call float @fdimf(float 1.500000e+00, float 8.0)
+  ret float %dim
+}
+
+define float @fdim_float1() {
+; CHECK-LABEL: define float @fdim_float1() {
+; CHECK-NEXT:    ret float 2.000000e+00
+;
+  %dim = call float @fdimf(float 1.000000e+01, float 8.0)
+  ret float %dim
+}
+
+define double @fdim_poison1() {
+; CHECK-LABEL: define double @fdim_poison1() {
+; CHECK-NEXT:    [[DIM:%.*]] = call double @fdim(double poison, double 1.000000e+00)
+; CHECK-NEXT:    ret double [[DIM]]
+;
+  %dim = call double @fdim(double poison, double 1.0)
+  ret double %dim
+}
+
+define double @fdim_poison2() {
+; CHECK-LABEL: define double @fdim_poison2() {
+; CHECK-NEXT:    [[DIM:%.*]] = call double @fdim(double 1.000000e+00, double poison)
+; CHECK-NEXT:    ret double [[DIM]]
+;
+  %dim = call double @fdim(double 1.0, double poison)
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braw-lee wrote:

m_APFloat() would not match against undef/poison values
so i used m_Undef() to find any undef/poison values, and returned them

https://github.com/llvm/llvm-project/pull/109235