[clang] [llvm] [HLSL] implement the `isinf` intrinsic (PR #84927)

[Justin Bogner via cfe-commits]

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@@ -18050,6 +18050,21 @@ Value *CodeGenFunction::EmitHLSLBuiltinExpr(unsigned BuiltinID,
         /*ReturnType=*/Op0->getType(), Intrinsic::dx_frac,
         ArrayRef<Value *>{Op0}, nullptr, "dx.frac");
   }
+  case Builtin::BI__builtin_hlsl_elementwise_isinf: {
+    Value *Op0 = EmitScalarExpr(E->getArg(0));
+    llvm::Type *Xty = Op0->getType();
+    llvm::Type *retType = llvm::Type::getInt1Ty(this->getLLVMContext());
+    if (Xty->isVectorTy()) {
+      auto *XVecTy = E->getArg(0)->getType()->getAs<VectorType>();
+      retType = llvm::VectorType::get(
+          retType, ElementCount::getFixed(XVecTy->getNumElements()));
+    }
+    if (!E->getArg(0)->getType()->hasFloatingRepresentation())
+      llvm_unreachable("isinf operand must have a float representation");
+    return Builder.CreateIntrinsic(
+        /*ReturnType=*/retType, Intrinsic::dx_isinf, ArrayRef<Value *>{Op0},
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bogner wrote:

I see that this is just following the rest of the file so I guess no change needed, but it seems odd to tag "/*ReturnType=*/" here specifically - we usually only do that for bools and things that are ambiguous, where this is literally passing an argument called `retType`.

https://github.com/llvm/llvm-project/pull/84927