[clang] [llvm] [HLSL] Add wave prefix count bits function (PR #178059)

[Tex Riddell via cfe-commits]

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@@ -57,6 +57,7 @@ bool DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable(
   case Intrinsic::dx_rsqrt:
   case Intrinsic::dx_saturate:
   case Intrinsic::dx_splitdouble:
+  case Intrinsic::dx_wave_prefix_bit_count:
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tex3d wrote:

Since this doesn't support vectors, does it belong here?

https://github.com/llvm/llvm-project/pull/178059