[TargetVersion] Only enable on RISC-V and AArch64

Author: BeMg

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3282,6 +3282,8 @@ def warn_unsupported_target_attribute
               "attribute string; '%select{target|target_clones|target_version}3' "
               "attribute ignored">,
       InGroup<IgnoredAttributes>;
+def err_target_version_unsupported
+    : Error<"target_version attribute is not supported in this target">;
 def err_attribute_unsupported
     : Error<"%0 attribute is not supported on targets missing %1;"
             " specify an appropriate -march= or -mcpu=">;

clang/lib/Sema/SemaDeclAttr.cpp

@@ -3040,6 +3040,11 @@ bool Sema::checkTargetVersionAttr(SourceLocation LiteralLoc, Decl *D,
   enum FirstParam { Unsupported };
   enum SecondParam { None };
   enum ThirdParam { Target, TargetClones, TargetVersion };
+
+  if (!Context.getTargetInfo().getTriple().isRISCV() &&
+      !Context.getTargetInfo().getTriple().isAArch64())
+    return Diag(LiteralLoc, diag::err_target_version_unsupported);
+
   llvm::SmallVector<StringRef, 8> Features;
   if (Context.getTargetInfo().getTriple().isRISCV()) {
     llvm::SmallVector<StringRef, 8> AttrStrs;