[clang] [llvm] Add length HLSL function to DirectX Backend (PR #101256)

[Farzon Lotfi via llvm-commits]

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@@ -18460,6 +18460,22 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         /*ReturnType=*/X->getType(), CGM.getHLSLRuntime().getLerpIntrinsic(),
         ArrayRef<Value *>{X, Y, S}, nullptr, "hlsl.lerp");
   }
+  case Builtin::BI__builtin_hlsl_elementwise_length: {
+    Value *X = EmitScalarExpr(E->getArg(0));
+    
+    if (!E->getArg(0)->getType()->hasFloatingRepresentation())
+      llvm_unreachable("length operand must have a float representation");
+    // if the operand is a scalar, we can use the fabs llvm intrinsic directly
+    if (!E->getArg(0)->getType()->isVectorType()) {
+      llvm::Type *ResultType = ConvertType(E->getType());
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farzonl wrote:

Is there a reason you don't just call `EmitFAbs`? Seems to be what others are doing in this file.

https://github.com/llvm/llvm-project/pull/101256