[clang] [Win/X86] Make _m_prefetch[w] builtins to avoid winnt.h conflicts (PR #115099)

[Phoebe Wang via cfe-commits]

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@@ -138,6 +142,12 @@ let Attributes = [Const, NoThrow, RequiredVectorWidth<256>], Features = "avx" in
   }
 }
 
+// PRFCHW
+let Features = "prfchw", Header = "x86intrin.h", Attributes = [NoThrow, Const] in {
+  def _m_prefetch : X86LibBuiltin<"void(void *)">;
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phoebewang wrote:

Only `_m_prefetchw` requires "prfchw". `_m_prefetch` can be put together with `_mm_prefetch`.

https://github.com/llvm/llvm-project/pull/115099