[clang] [clang][CUDA] Define _NV_RSQRT_SPECIFIER for glibc-2.42/cuda-13.2 compatibility (PR #185701)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Artem Belevich (Artem-B)

<details>
<summary>Changes</summary>

CUDA-13.2 defines _NV_RSQRT_SPECIFIER to make its headers compileable with glibc 2.42+. However, clang does not include the header that defines the macro, and has to define it by itself.

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Full diff: https://github.com/llvm/llvm-project/pull/185701.diff


1 Files Affected:

- (modified) clang/lib/Headers/__clang_cuda_runtime_wrapper.h (+15) 


``````````diff
diff --git a/clang/lib/Headers/__clang_cuda_runtime_wrapper.h b/clang/lib/Headers/__clang_cuda_runtime_wrapper.h
index fcf1ea89ad6a3..3ed023b9c72d7 100644
--- a/clang/lib/Headers/__clang_cuda_runtime_wrapper.h
+++ b/clang/lib/Headers/__clang_cuda_runtime_wrapper.h
@@ -45,6 +45,21 @@
 #include <string.h>
 #undef __CUDACC__
 
+// math_functions.h from CUDA 13.2+ defines _NV_RSQRT_SPECIFIER.
+// Clang does not include it, so we need to define it ourselves.
+#if defined(__GNUC__)
+# include <features.h> /* For GLIBC macros */
+# if defined(__GLIBC_PREREQ)
+#  if __GLIBC_PREREQ(2, 42)
+#   define _NV_RSQRT_SPECIFIER noexcept(true)
+#  endif
+# endif
+#endif
+
+#ifndef _NV_RSQRT_SPECIFIER
+# define _NV_RSQRT_SPECIFIER
+#endif
+
 // Preserve common macros that will be changed below by us or by CUDA
 // headers.
 #pragma push_macro("__THROW")

``````````

</details>


https://github.com/llvm/llvm-project/pull/185701