[llvm] [NVPTX][NFC] Use same logic to get alignment in param declarations and function prototypes (PR #98220)

[Kevin McAfee via llvm-commits]

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@@ -1438,10 +1438,8 @@ std::string NVPTXTargetLowering::getPrototype(
 
     if (!Outs[OIdx].Flags.isByVal()) {
       if (IsTypePassedAsArray(Ty)) {
-        const CallInst *CallI = cast<CallInst>(&CB);
         Align ParamAlign =
-            getAlign(*CallI, i + AttributeList::FirstArgIndex)
-                .value_or(getFunctionParamOptimizedAlign(F, Ty, DL));
+            getArgumentAlignment(&CB, Ty, i + AttributeList::FirstArgIndex, DL);
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kalxr wrote:

If there is no alignment metadata or the call is indirect, the `getArgumentAlignment` path ultimately uses `getFunctionParamOptimizedAlign`. If the call is indirect it uses the ABI type alignment, which `getFunctionParamOptimizedAlign` does as well, so we shouldn't lose out on opportunities for increased alignments.

Unfortunately, I don't think we can test that the increased alignment remains right now. We only emit prototypes for indirect calls, which would use the ABI type alignment.

https://github.com/llvm/llvm-project/pull/98220