[clang] [MSVC, ARM64] Fix signature for __prefetch (PR #93235)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Daniel Paoliello (dpaoliello)

<details>
<summary>Changes</summary>

#<!-- -->67174 added the `__prefetch` intrinsic, however it used the wrong signature: the argument should be `const void*`, not `void*`.

Docs: https://learn.microsoft.com/en-us/cpp/intrinsics/arm64-intrinsics?view=msvc-170#:~:text=__prefetch

Unfortunately, this can't be backported (there are no more 18.x releases, and this change is a breaking change), so I'll see if I can get a workaround added on MSVC's side for Clang 18.

---
Full diff: https://github.com/llvm/llvm-project/pull/93235.diff


2 Files Affected:

- (modified) clang/include/clang/Basic/BuiltinsAArch64.def (+1-1) 
- (modified) clang/lib/Headers/intrin.h (+1-1) 


``````````diff
diff --git a/clang/include/clang/Basic/BuiltinsAArch64.def b/clang/include/clang/Basic/BuiltinsAArch64.def
index cf8711c6eaee3..5f53c98167dfb 100644
--- a/clang/include/clang/Basic/BuiltinsAArch64.def
+++ b/clang/include/clang/Basic/BuiltinsAArch64.def
@@ -290,7 +290,7 @@ TARGET_HEADER_BUILTIN(_CountLeadingZeros64, "UiULLi", "nh", INTRIN_H, ALL_MS_LAN
 TARGET_HEADER_BUILTIN(_CountOneBits, "UiUNi", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
 TARGET_HEADER_BUILTIN(_CountOneBits64, "UiULLi", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
 
-TARGET_HEADER_BUILTIN(__prefetch, "vv*", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
+TARGET_HEADER_BUILTIN(__prefetch, "vvC*", "nh", INTRIN_H, ALL_MS_LANGUAGES, "")
 
 #undef BUILTIN
 #undef LANGBUILTIN
diff --git a/clang/lib/Headers/intrin.h b/clang/lib/Headers/intrin.h
index 7eb6dceaabfae..5ceb986a1f652 100644
--- a/clang/lib/Headers/intrin.h
+++ b/clang/lib/Headers/intrin.h
@@ -378,7 +378,7 @@ unsigned int _CountLeadingSigns64(__int64);
 unsigned int _CountOneBits(unsigned long);
 unsigned int _CountOneBits64(unsigned __int64);
 
-void __cdecl __prefetch(void *);
+void __cdecl __prefetch(const void *);
 #endif
 
 /*----------------------------------------------------------------------------*\

``````````

</details>


https://github.com/llvm/llvm-project/pull/93235