[llvm] [NVPTX][NFC] Refactor and cleanup NVPTXISelLowering call lowering 2/n (PR #137666)

[Artem Belevich via llvm-commits]

================
@@ -1778,20 +1731,19 @@ SDValue NVPTXTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     CalleeFunc->addFnAttr("nvptx-libcall-callee", "true");
   }
 
-  if (isIndirectCall) {
+  if (IsIndirectCall) {
     // This is indirect function call case : PTX requires a prototype of the
     // form
     // proto_0 : .callprototype(.param .b32 _) _ (.param .b32 _);
     // to be emitted, and the label has to used as the last arg of call
     // instruction.
     // The prototype is embedded in a string and put as the operand for a
     // CallPrototype SDNode which will print out to the value of the string.
-    SDVTList ProtoVTs = DAG.getVTList(MVT::Other, MVT::Glue);
     std::string Proto = getPrototype(
-        DL, RetTy, Args, Outs, retAlignment,
+        DL, RetTy, Args, CLI.Outs, RetAlign,
         HasVAArgs
-            ? std::optional<std::pair<unsigned, const APInt &>>(std::make_pair(
-                  CLI.NumFixedArgs, VADeclareParam->getConstantOperandAPInt(1)))
+            ? std::optional<std::pair<unsigned, unsigned>>(std::make_pair(
+                  CLI.NumFixedArgs, VADeclareParam.getConstantOperandVal(1)))
----------------
Artem-B wrote:

We could let compiler deduce the template parameters and skip make_pair.
```
std::optional(std::pair(CLI.NumFixedArgs, VADeclareParam.getConstantOperandVal(1)))
```

https://github.com/llvm/llvm-project/pull/137666