[clang] Reapply "[Win/X86] Make _m_prefetch[w] builtins to avoid winnt.h conflicts (#115099)" (PR #138360)

[Phoebe Wang via cfe-commits]

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@@ -138,6 +138,12 @@ let Attributes = [Const, NoThrow, RequiredVectorWidth<256>], Features = "avx" in
   }
 }
 
+// PRFCHW
+let Features = "prfchw", Header = "intrin.h", Attributes = [NoThrow, Const] in {
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phoebewang wrote:

Although they are in the same file, both don't have "prfchw" feature in prior defination. I'm not sure if it's due to it's used by cl mode only, but I'm afraid the change here may result in compatiablilty issues.

https://github.com/llvm/llvm-project/pull/138360