[clang] [llvm] Add step builtins and step HLSL function to DirectX and SPIR-V backend (PR #106471)

[Farzon Lotfi via cfe-commits]

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@@ -1490,6 +1490,18 @@ bool SemaHLSL::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
     TheCall->setType(ArgTyA);
     break;
   }
+  case Builtin::BI__builtin_hlsl_step: {
+    if (CheckFloatOrHalfRepresentations(&SemaRef, TheCall))
+      return true;
+    if (SemaRef.checkArgCount(TheCall, 2))
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farzonl wrote:

NIT: we usually check the arg count first. 

https://github.com/llvm/llvm-project/pull/106471