[clang] [Clang] Support constexpr for AVX512 compress intrinsics (PR #187656)

[Simon Pilgrim via cfe-commits]

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@@ -3550,6 +3550,38 @@ static bool interp__builtin_ia32_vpconflict(InterpState &S, CodePtr OpPC,
   return true;
 }
 
+static bool interp__builtin_ia32_compress(InterpState &S, CodePtr OpPC,
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RKSimon wrote:

an APInt would be better - then the `compressMask &= (1 << numElts) - 1;` can be done more safely 

https://github.com/llvm/llvm-project/pull/187656