[clang] [clang][RISCV] Enable RVV with function attribute __attribute__((target("arch=+v"))) (PR #83674)

[Brandon Wu via cfe-commits]

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@@ -8927,8 +8927,13 @@ void Sema::CheckVariableDeclarationType(VarDecl *NewVD) {
     }
   }
 
-  if (T->isRVVSizelessBuiltinType())
-    checkRVVTypeSupport(T, NewVD->getLocation(), cast<Decl>(CurContext));
+  if (T->isRVVSizelessBuiltinType() && isa<FunctionDecl>(CurContext)) {
+    const FunctionDecl *FD = cast<FunctionDecl>(CurContext);
+    llvm::StringMap<bool> CallerFeatureMap;
+    Context.getFunctionFeatureMap(CallerFeatureMap, FD);
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4vtomat wrote:

> > But we don't have the FunctionDecl info in the RISCVTargetInfo::initFeatureMap call.
> 
> What about keeping this map in ASTContext instead?

I guess it might be a feasible solution, however the memory usage might increase since it has to keep the map for each function during the lifetime of the ASTContext.
@topperc Do you think we can do this? Or we can leave it in TODO until it becomes a problem in some real cases.

https://github.com/llvm/llvm-project/pull/83674