[clang] [llvm] [HLSL] Implement the `fwidth` intrinsic for DXIL and SPIR-V target (PR #161378)

[Alexander Johnston via cfe-commits]

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@@ -162,6 +162,8 @@ def int_dx_splitdouble : DefaultAttrsIntrinsic<[llvm_anyint_ty, LLVMMatchType<0>
     [LLVMScalarOrSameVectorWidth<0, llvm_double_ty>], [IntrNoMem]>;
 def int_dx_radians : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>], [IntrNoMem]>;
 def int_dx_discard : DefaultAttrsIntrinsic<[], [llvm_i1_ty], []>;
+def int_dx_deriv_coarse_x : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>], [IntrNoMem]>;
+def int_dx_deriv_coarse_y : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>], [IntrNoMem]>;
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Alexander-Johnston wrote:

A fair point! I'll finish implementing them fully and put them in a new PR, then come back to finish up fwidth.

https://github.com/llvm/llvm-project/pull/161378