[clang] [Clang] Fix __cpuidex conflict with CUDA (PR #152556)

[Nick Sarnie via cfe-commits]

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@@ -345,10 +345,15 @@ static __inline int __get_cpuid_count (unsigned int __leaf,
 // In some configurations, __cpuidex is defined as a builtin (primarily
 // -fms-extensions) which will conflict with the __cpuidex definition below.
 #if !(__has_builtin(__cpuidex))
+// In some cases, offloading will set the host as the aux triple and define the
+// builtin. Given __has_builtin does not detect builtins on aux triples, we need
+// to explicitly check for some offloading cases.
+#ifndef __NVPTX__
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sarnex wrote:

Thanks so much for the quick investigation!

I'm not really familiar with CUDA offloading but if the `cc1` command is `cc1 -triple nvptx64-nvidia-cuda -aux-triple x86_64-unknown-linux-gnu`, `__has_builtin(__cpuidex)` returning false seems correct, so I would think the actual root cause is that `cpuidex` is getting defined for CUDA with `nvptx64-nvidia-cuda -aux-triple x86_64-unknown-linux-gnu`. 

If so, I'm happy to have this workaround for now but we might want to file a tracker somewhere for the root cause to be investigated.



https://github.com/llvm/llvm-project/pull/152556