[clang] [llvm] [HLSL] Implement dot2add intrinsic (PR #131237)

[Farzon Lotfi via llvm-commits]

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@@ -45,6 +45,14 @@ distance_vec_impl(vector<T, N> X, vector<T, N> Y) {
   return length_vec_impl(X - Y);
 }
 
+constexpr float dot2add_impl(half2 a, half2 b, float c) {
+#if defined(__DIRECTX__)
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farzonl wrote:

there is no lowercase `__directx__`. and the lowercase spirv one was only just added last week so you won't see any code in our headers use lowercase `__spirv__` either.

https://github.com/llvm/llvm-project/pull/131237