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

[Luke Lau 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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lukel97 wrote:

> > @4vtomat if the MCPU has a feature but the function explicitly disables it then I think we want the `-`
> 
> Why don't we just remove it from feature map?

We also need the negative extensions if the target attribute string is a complete arch, e.g. `__attribute__((target="arch=rv64i")))`, because any extensions from mcpu need to be turned off.

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