[clang] [llvm] [HLSL][DXIL] Implement `refract` intrinsic (PR #136026)

[via cfe-commits]

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@@ -71,6 +71,27 @@ constexpr vector<T, L> reflect_vec_impl(vector<T, L> I, vector<T, L> N) {
 #endif
 }
 
+template <typename T> constexpr T refract_impl(T I, T N, T eta) {
+  T k = 1 - eta * eta * (1 - (N * I * N *I));
+  if(k < 0)
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raoanag wrote:

the latest commit uses select, but the hlsl tests have not been updated, will decide next steps based on offline discuss

https://github.com/llvm/llvm-project/pull/136026