[clang] [llvm] [HLSL] Implement the `smoothstep` intrinsic (PR #132288)

[Farzon Lotfi via llvm-commits]

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@@ -101,6 +101,52 @@ bool SemaSPIRV::CheckSPIRVBuiltinFunctionCall(unsigned BuiltinID,
     TheCall->setType(RetTy);
     break;
   }
+  case SPIRV::BI__builtin_spirv_smoothstep: {
+    if (SemaRef.checkArgCount(TheCall, 3))
+      return true;
+
+    // check if the all arguments have floating representation
+    ExprResult A = TheCall->getArg(0);
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farzonl wrote:

it might be worth looping over the args and checking `hasFloatingRepresentation` for each arg to determing which diag to emit. Feel free to write a helper if you need it.

https://github.com/llvm/llvm-project/pull/132288