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

[Alexander Johnston via llvm-commits]

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@@ -21,3 +21,4 @@ def subgroup_local_invocation_id : SPIRVBuiltin<"uint32_t()", [NoThrow, Const]>;
 def distance : SPIRVBuiltin<"void(...)", [NoThrow, Const]>;
 def length : SPIRVBuiltin<"void(...)", [NoThrow, Const]>;
 def smoothstep : SPIRVBuiltin<"void(...)", [NoThrow, Const, CustomTypeChecking]>;
+def fwidth : SPIRVBuiltin<"void(...)", [NoThrow, Const, CustomTypeChecking]>;
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Alexander-Johnston wrote:

Moved to BuiltinsSPIRVVK.td

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