[clang] [Clang][HIP] Deprecate the AMDGCN_WAVEFRONT_SIZE macros (PR #112849)

[Andrey Alekseenko via cfe-commits]

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@@ -337,9 +337,12 @@ void AMDGPUTargetInfo::getTargetDefines(const LangOptions &Opts,
   if (hasFastFMA())
     Builder.defineMacro("FP_FAST_FMA");
 
-  Builder.defineMacro("__AMDGCN_WAVEFRONT_SIZE__", Twine(WavefrontSize));
-  // ToDo: deprecate this macro for naming consistency.
-  Builder.defineMacro("__AMDGCN_WAVEFRONT_SIZE", Twine(WavefrontSize));
+  Builder.defineMacro("__AMDGCN_WAVEFRONT_SIZE__", Twine(WavefrontSize),
+                      "compile-time-constant access to the wavefront size will "
+                      "be removed in a future release");
+  Builder.defineMacro("__AMDGCN_WAVEFRONT_SIZE", Twine(WavefrontSize),
+                      "compile-time-constant access to the wavefront size will "
+                      "be removed in a future release");
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al42and wrote:

The use we currently have in our project is to detect, via CMake's `try_compile`, whether we have Wave64 or Wave32 targets (or both) to later choose which data structure flavors to instantiate. With the macro, we can easily do `#if`+`#warning` inside a kernel, and then parse the build log.

Without it, the only solution we found was to parse the list of targets, which feels more brittle. `__builtin_amdgcn_wavefrontsize()` is not a compile-time constant expression, so cannot be used for such checks. Am I missing something? What is the planned timeline for the removal of this macro?

https://github.com/llvm/llvm-project/pull/112849