[clang] [llvm] [HLSL] Implement the `reflect` HLSL function (PR #122992)

[Farzon Lotfi via llvm-commits]

================
@@ -3030,6 +3031,15 @@ bool SPIRVInstructionSelector::selectIntrinsic(Register ResVReg,
     return selectExtInst(ResVReg, ResType, I, CL::fract, GL::Fract);
   case Intrinsic::spv_normalize:
     return selectExtInst(ResVReg, ResType, I, CL::normalize, GL::Normalize);
+  case Intrinsic::spv_reflect:
+    if (!STI.canUseExtInstSet(SPIRV::InstructionSet::InstructionSet::GLSL_std_450)) {
----------------
farzonl wrote:

Not a bad idea, but in another pr. so that the changes here are more focused to the reflect feature. Feel free to file an issue and identify some tests to add.

https://github.com/llvm/llvm-project/pull/122992