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

[via cfe-commits]

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+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang_cc1 -finclude-default-header -triple \
+// RUN:   dxil-pc-shadermodel6.3-library %s -fnative-half-type \
+// RUN:   -emit-llvm -O1 -o - | FileCheck %s
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raoanag wrote:

I was referring [reflect.ll](https://github.com/llvm/llvm-project/blob/e8825900838a11afe326e202d19a3df6e3408422/clang/test/CodeGenHLSL/builtins/reflect.hlsl#L1C1-L1C100) and [smoothstep.ll](https://github.com/llvm/llvm-project/blob/e8825900838a11afe326e202d19a3df6e3408422/clang/test/CodeGenHLSL/builtins/smoothstep.hlsl#L1C1-L1C100) both contain the note and `O1` flag. but I will these take off from `refract.hlsl`

Is this something that needs to be updated for all files under `clang/test/CodeGenHLSL/builtins/` or just the refract operator?

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