[clang] [AArch64][SME] Add diagnostics to CheckConstexprFunctionDefinition (PR #121777)

[via cfe-commits]

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@@ -1854,6 +1855,9 @@ bool Sema::CheckConstexprFunctionDefinition(const FunctionDecl *NewFD,
     }
   }
 
+  if (Context.getTargetInfo().getTriple().isAArch64())
+    ARM().CheckSMEFunctionDefAttributes(NewFD);
+
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cor3ntin wrote:

This seems like a weird place to do that (afaict this has nothing to do with constexpr) and I am not sure this code is tested. I suspect `ActOnStartOfLambdaDefinition` - after the `ProcessDeclAttributes` call might be a better place 

https://github.com/llvm/llvm-project/pull/121777