Warn about using the new force_align_arg_pointer attribute on a function

pointer. If you don't like the new warning, you can turn it off with
-Wno-force-align-arg-pointer.

llvm-svn: 95939

clang/include/clang/Basic/DiagnosticGroups.td

@@ -119,6 +119,7 @@ def VectorConversions : DiagGroup<"vector-conversions">;      // clang specific
 def VolatileRegisterVar : DiagGroup<"volatile-register-var">;
 def : DiagGroup<"write-strings">;
 def CharSubscript : DiagGroup<"char-subscripts">;
+def ForceAlignArgPointer : DiagGroup<"force-align-arg-pointer">;
 
 // Aggregation warning settings.
 
@@ -179,4 +180,4 @@ def : DiagGroup<"comments", [Comment]>;         // -Wcomments = -Wcomment
 // A warning group for warnings that we want to have on by default in clang,
 // but which aren't on by default in GCC.
 def NonGCC : DiagGroup<"non-gcc",
-    [SignCompare, Conversion]>;
+    [SignCompare, Conversion, ForceAlignArgPointer]>;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -722,6 +722,9 @@ def err_attribute_aligned_not_power_of_two : Error<
 def warn_redeclaration_without_attribute_prev_attribute_ignored : Warning<
   "'%0' redeclared without %1 attribute: previous %1 ignored">;
 def warn_attribute_ignored : Warning<"%0 attribute ignored">;
+def warn_faap_attribute_ignored : Warning<
+  "force_align_arg_pointer used on function pointer; attribute ignored">,
+  InGroup<ForceAlignArgPointer>;
 def warn_attribute_precede_definition : Warning<
   "attribute declaration must precede definition">;
 def warn_attribute_void_function : Warning<

clang/lib/Sema/TargetAttributesSema.cpp

@@ -79,12 +79,14 @@ static void HandleX86ForceAlignArgPointerAttr(Decl *D,
     return;
   }
 
-  // If we try to apply it to a function pointer, don't warn, but don't
-  // do anything, either. It doesn't matter anyway, because there's nothing
-  // special about calling a force_align_arg_pointer function.
+  // If we try to apply it to a function pointer, warn. This is a special
+  // instance of the warn_attribute_ignored warning that can be turned
+  // off with -Wno-force-align-arg-pointer.
   ValueDecl* VD = dyn_cast<ValueDecl>(D);
-  if (VD && VD->getType()->isFunctionPointerType())
+  if (VD && VD->getType()->isFunctionPointerType()) {
+    S.Diag(Attr.getLoc(), diag::warn_faap_attribute_ignored);
     return;
+  }
   // Attribute can only be applied to function types.
   if (!isa<FunctionDecl>(D)) {
     S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type)

clang/test/Sema/x86-attr-force-align-arg-pointer.c

@@ -14,5 +14,5 @@ void d(void);
 void __attribute__((force_align_arg_pointer)) d(void) {}
 
 // Attribute is ignored on function pointer types.
-void (__attribute__((force_align_arg_pointer)) *p)();
+void (__attribute__((force_align_arg_pointer)) *p)(); //expected-warning{{force_align_arg_pointer used on function pointer; attribute ignored}}