[clang] [CLANG] Add warning when INF or NAN are used in a binary operation or as function argument in fast math mode. (PR #76873)

[Matt Arsenault via cfe-commits]

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+// RUN: %clang_cc1 -x c++ -verify -triple powerpc64le-unknown-unknown %s \
+// RUN: -menable-no-infs -menable-no-nans  -DFAST=1
+
+// RUN: %clang_cc1 -x c++ -verify -triple powerpc64le-unknown-unknown %s \
+// RUN: -DNOFAST=1
+
+// RUN: %clang_cc1 -x c++ -verify -triple powerpc64le-unknown-unknown %s \
+// RUN: -menable-no-infs -DNO_INFS=1
+
+// RUN: %clang_cc1 -x c++ -verify -triple powerpc64le-unknown-unknown %s \
+// RUN: -menable-no-nans -DNO_NANS=1
+
+int isunorderedf (float x, float y);
+#if NOFAST
+// expected-no-diagnostics
+#endif
+extern "C++" {
+namespace std __attribute__((__visibility__("default"))) {
+  bool
+  isinf(float __x);
+  bool
+  isinf(double __x);
+  bool
+  isinf(long double __x);
+  bool
+  isnan(float __x);
+  bool
+  isnan(double __x);
+  bool
+  isnan(long double __x);
+bool
+  isfinite(float __x);
+  bool
+  isfinite(double __x);
+  bool
+  isfinte(long double __x);
+ bool
+  isunordered(float __x, float __y);
+  bool
+  isunordered(double __x, double __y);
+  bool
+  isunordered(long double __x, long double __y);
+} // namespace )
+}
+#define NAN (__builtin_nanf(""))
+#define INFINITY (__builtin_inff())
+
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arsenm wrote:

What about through std::numeric_limits<T>::infinity?

https://github.com/llvm/llvm-project/pull/76873