[GCC] PR23529 Mangler part of attrbute abi_tag support

[DmitryPolukhin]

Summary

Original patch by Stefan Bühler http://reviews.llvm.org/D12834

Difference between original and this one:

• fixed all failing tests
• fixed mangling for global variable outside namespace
• emit ABI tags for guards and local names (i.e. GCC ABI 10+)
• clang-format + other stylistic changes
• significantly reworked patch according to Richard's suggestions

Sema part is here: http://reviews.llvm.org/D17567

[DmitryPolukhin]

Re-base to resolve merge conflicts with r263109.

[majnemer]

lib/AST/ItaniumMangle.cpp

217–218

Please add a comment describe this state.

333

Please use = instead of list initialization.

336

Variables start with an uppercase letter.

343–344

const typically goes before the type.

367

Don't use dyn_cast if you aren't going to use the value, use isa instead.

368–369

commented out code?

398

Sentences in LLVM comments start with a capital letter and end with a period.

431

Is this clang-format'd?

622–623

Why do you have an assert and check for that the pointer is not null?

798

Use const auto * if the type is obvious from the RHS.

1422

Variables start with an upper case letter.

4519–4520

I think a noun is missing between "for" and "but".

[rnk]

lib/AST/ItaniumMangle.cpp

272–294

I think it would be a valuable exercise to write up something more concrete than this in a .rst file in docs/. I think part of the reason why this patch has languished so long is because there is no specification or documentation to speak of. This new abi_tag is a major departure from the wonderful *standard* Itanium C++ ABI that Unix has enjoyed. On Windows, we suffer greatly from having to follow each and every implementation detail that Microsoft accidentally baked into their ABI. It would be good if we could put together a document that we could send back to someone who works on GCC, so that they can verify that that is how abi_tag is intended to work, even if GCC deviates from it in some places.

test/SemaCXX/attr-abi-tag.cpp

1 ↗

(On Diff #50416)

This doesn't seem like a Sema test. Maybe fold it into the mangling test?

[DmitryPolukhin]

All comments resolved.

PTAL

lib/AST/ItaniumMangle.cpp

272–294

It was part of previous commit with syntax of the attribute, please see http://clang.llvm.org/docs/ItaniumMangleAbiTags.html

Also as far as I understand, Jason Merrill is going to write some document about it, see https://llvm.org/bugs/show_bug.cgi?id=23529#c58 a

431

Yes, that is how clang-format formats this in-class {}-initializer. But I removed it and replaced with initialization in c-tor.

[rjmccall]

It's languished because the idea itself has unavoidable problems with incomplete types.

[rsmith]

lib/AST/ItaniumMangle.cpp

272–299

Just reference the documentation for most of this, you don't need to duplicate so much of the description here.

275

build -> built

321–323

Do we need to? IIUC, the only time we need this list is when determining the set of "available" tags for a function declaration with a tagged return type, and in that case, a tag can only be available from a substitution if it's also available from the target of that substitution (right?).

326–328

It seems unnecessarily expensive to hold these as std::sets.

348–361

Why do we need a stack of these? It seems like we only need one set of available tags for the complete mangling process (it should only be used once at the top level).

[DmitryPolukhin]

Fixed comments.

PTAL

lib/AST/ItaniumMangle.cpp

321–323

It is not only for functions but also for variables but yes, as far as I understand, substitution itself cannot add tags and target should have all tags. I removed FIXME.

348–361

Stack is required for mangling local names. In that case we have more than one list of available tags and it can be enclosed.

[DmitryPolukhin]

Friendly ping, please take a look!

[DmitryPolukhin]

Richard, Reid and David,

Friendly ping, please take a look to this patch. If there are no more comments/suggestion, I think it is better to commit this patch iterate on GCC abi_tag support based on users' feedback.

[DmitryPolukhin]

Richard, this is just weekly friendly ping about abi_tag support.

Please let me know if you think if something in this patch needs improvements or you are waiting for something specific before committing this patch.

[DmitryPolukhin]

Weekly friendly ping, PTAL!

[rnk]

I think Richard has a counterexample that shows that the "NullOut" approach to computing abi_tag sets isn't the right way to go. I wasn't able to craft it myself, but I figured I should send along the feedback that maybe a separate, up-front pass over the return type with a custom TypeVisitor might be a better way to do this.

[DmitryPolukhin]

Richard, could you please share your counterexample so I could test it on my patch and GCC?

As for separate pass, it was my first reaction on the original patch from Stefan but soon I realized that I'll have to copy parts of magnler to some simplified mangler but with high probability of forgetting something and with code duplication. So now I think approach which runs full mangler in special mode is better and less error prone.

[DmitryPolukhin]

+ rebase
+ added testcase with Richard's example

[foutrelis]

test/CodeGenCXX/mangle-abi-tag.cpp

116

I'm seeing a test failure on i686 on Arch Linux (all tests pass on x86_64):

mangle-abi-tag-test-failure-on-i686.log1 KBDownload

I'm using this patch and a slightly tweaked version of D17567 on top of clang 3.8.0; not sure if that's the reason for the failure.

[DmitryPolukhin]

Thank you for reporting this issue, I'll take a look.
I'm mostly testing on x86_64 so I may not notice the problem.

[kerberizer]

Just to confirm seeing exactly the same error as @foutrelis on Arch i686 (and everything else pass too), but when building the current 3.9.0svn trunk with only this patch applied unmodified on it. Thus, it's probably not likely to be something connected to Evangelos' specific setup.

[DmitryPolukhin]

• fixed tests for i686 when function may have hidden parameter

[kerberizer]

@DmitryPolukhin: Dmitry, all tests now pass fine on my setup, both on i686 and x86_64. Thanks for taking care of this issue!

[DmitryPolukhin]

Richard, friendly ping. It seems that your counterexample cause no issue with this patch. I added tests to prove it. Could you please take another look?

[DmitryPolukhin]

One more friendly ping...... :(

[kerberizer]

Dmitry, for a few days now I'm seeing another regression test failure. It has most likely appeared in the 6 hours frame after r269852, because that's the period of my automatic builds, and r269852 was the last to pass the tests successfully. The failure this time is on both x86_64 and i686:

mangle-abi-tag-test-failure-2.log1 KBDownload

[DmitryPolukhin]

Fix test/PCH/attrs.c failure due to warning about unsupported abi_tag attribute (committed in rL269869).
This patch implements abi_tag so the warning is not expected with this patch.

[rengolin]

Ping?

Can we get some traction on this one, please? The 3.8.1 deadline is tomorrow and I'd really like to see these two patches (plus the related fixes) in it, or some LTS Linux distributions will live without them, and thus with completely broken copies of LLVM.

FWIW, multiple people seem to have tested it and reported good results. Also, Arch Linux has had the patch for several months, without a hiccup, probably others, too.

I think we can get this one in as it is, and maybe apply fixes later if relevant.

cheers,
--renato

[majnemer]

In D18035#434095, @DmitryPolukhin wrote:

One more friendly ping...... :(

I think the best way to make progress on this is to refactor this patch along the lines @rsmith suggested back on May 3.

[rsmith]

In D18035#437715, @rengolin wrote:

The 3.8.1 deadline is tomorrow and I'd really like to see these two patches (plus the related fixes) in it,

Realistically, this seems unlikely to make it in time.

or some LTS Linux distributions will live without them, and thus with completely broken copies of LLVM.

No, they'll be shipping with a broken copy of their C++ standard library, and will fail to conform to the Linux Standards Base specifications due to deviating from the Itanium C++ ABI. This patch is working around another popular implementation's failure to follow the relevant specification, nothing more. Please try to appropriately apportion the responsibility here; if your distribution opted into a non-standard ABI for their C++ standard library, you should point out to them that they made a mistake.

[ismail]

Richard,

Does this mean this feature will never be accepted? It would help to make a clear statement on this issue. I am not happy how this feature is introduced but it's too late now that every big Linux distro out there switched to the new ABI.

[• ttanner]

In D18035#440107, @rsmith wrote:

No, they'll be shipping with a broken copy of their C++ standard library, and will fail to conform to the Linux Standards Base specifications due to deviating from the Itanium C++ ABI. This patch is working around another popular implementation's failure to follow the relevant specification, nothing more. Please try to appropriately apportion the responsibility here; if your distribution opted into a non-standard ABI for their C++ standard library, you should point out to them that they made a mistake.

The new ABI is the de facto standard and we have to live with it, or at least support it.
It's too late to convince the major distributions to choose another solution.

[jackpoz]

In D18035#440107, @rsmith wrote:

Please try to appropriately apportion the responsibility here

It has always been clear who created the issue, GCC ABI 11 are there to stay, with the result of having an unusable clang since Ubuntu 15.10 (at least in my case).
It's responsibility of clang developers to review and accept patches tho, please hit the "Merge" button so clang users can build their applications on recent distros without having to rely on GCC.

Thank you Dmitry for the effort put into this patch and into the weekly friendly pings, your perseverance is admirable.

[rengolin]

In D18035#440107, @rsmith wrote:

Please try to appropriately apportion the responsibility here; if your distribution opted into a non-standard ABI for their C++ standard library, you should point out to them that they made a mistake.

I think I have been clear enough on the bug and the list about responsibility... It is clear that the distros screwed that up on their own, and neither GCC not LLVM could do much to work around the complete lack of proper testing before such a big decision.

In no way I think this is something we could have done anything to prevent from happening, nor I'm assuming that this patch is the best way forward for the future.

I only asked this to be reviewed and accepted IFF it's the right (temporary) implementation, so that distros can pull those patches with a bit more confidence.

If it makes to 3.8.1, that'd make things a lot easier for *them* (not us). If it doesn't, it wouldn't make it much harder (they can already pull odd patches). But since this has been tested by many people, including active usage in distros, and it doesn't touch anything outside the ABI tag issue, we could have it in (at least on trunk), so that we can test it better ourselves until 3.9 branches.

I really don't want to pull this one in just before we branch. Nor just after. Regardless of who screwed up, having a fix would be good to LLVM as well, not just the distros.

cheers,
--renato

[hfinkel]

FYI: There is now a specification, see: http://sourcerytools.com/pipermail/cxx-abi-dev/2016-June/002919.html

[DmitryPolukhin]

In D18035#447473, @hfinkel wrote:

FYI: There is now a specification, see: http://sourcerytools.com/pipermail/cxx-abi-dev/2016-June/002919.html

For the records, this patch implements GCC 6 abi_tag semantic and to the best of my knowledge mangles everything same as GCC 6. To support GCC 5 semantic Clang will need -fabi-version command line flag to support multiple ABI versions. But as far as I can see, Richard is not going to approve this patch so it seems to be dead end.

[hfinkel]

In D18035#448002, @DmitryPolukhin wrote:

In D18035#447473, @hfinkel wrote:

FYI: There is now a specification, see: http://sourcerytools.com/pipermail/cxx-abi-dev/2016-June/002919.html

...

But as far as I can see, Richard is not going to approve this patch so it seems to be dead end.

At the last C++ committee meeting, I observed Richard reaching out to the Redhat folks to ask for a specification so that we could make sure we implemented this feature properly (i.e. as intended). Based on that, I'm fairly certain he's interested in seeing a solution here. We just received the first draft of that specification yesterday. As far as I can tell, Richard also is very busy, like many of us, and it can take time to get to things, even important things. I understand why this is frustrating, but please don't become discouraged.

Richard, can you comment on whether you still want the refactoring you suggested in light of Dmitry's responses?

[andreybokhanko]

In D18035#448057, @hfinkel wrote:

We just received the first draft of that specification yesterday.

Is this specification confidential? If not, why it hasn't been made available in this code review? Most puzzlingly, why it hasn't been shared with Dmitry, who obviously contributed the most towards making abi_tag supported in clang?

As far as I can tell, Richard also is very busy, like many of us, and it can take time to get to things, even important things. I understand why this is frustrating, but please don't become discouraged.

I understand that Richard is super-busy and apart of doing a lot of stuff himself also reviews *a ton* of other peoples' patches (I wonder how he finds time... probably saves on sleeping :-))

But what's wrong with letting us (Intel) carry on some burden and implement this particular piece? Seeing how this review is developing makes me... yeah, discouraged is the right word. :-(

Yours,

Andrey

Software Engineer
Intel Compiler Team

[hfinkel]

In D18035#450211, @andreybokhanko wrote:

In D18035#448057, @hfinkel wrote:

We just received the first draft of that specification yesterday.

Is this specification confidential?

The link was posted here: http://sourcerytools.com/pipermail/cxx-abi-dev/2016-June/002919.html - which is the mailing list where the C++ ABI specification is discussed.

If not, why it hasn't been made available in this code review?

It was, it was part of my comment.

Most puzzlingly, why it hasn't been shared with Dmitry, who obviously contributed the most towards making abi_tag supported in clang?

If he does not otherwise follow the cxx-abi-dev list, I assume he saw the link when I posted it.

Yours,

Andrey

Software Engineer
Intel Compiler Team

[rsmith]

Yes, I definitely want us to implement this for GCC compatibility. And now that we have a specification for this feature, we can evaluate whether this is doing the right thing. On that basis:

I still want this refactored so that the normally-mangled part of a function name is only mangled once, rather than being mangled twice (once to find the implicit tag set and once to actually produce the mangled name). As suggested, you can achieve this by first computing the set of tags from the return type, then mangling the encoding to a separate buffer (collecting tags as you go) if the set is non-empty, and finally writing any remaining tags and the buffer contents.

Please factor out a function to mangle the source name and ABI tags for a NamedDecl rather than duplicating that pair of calls throughout the patch.

Current discussion on the ABI list suggests that it is not correct to mangle the return type / variable type to get the implicit tag set. The set of available attributes should be determined by a recursive walk of the original type (prior to any substitution), not by mangling it and seeing what it references. It's not yet clear whether that's the actual design intent or just the emergent behavior of the GCC implementation, however.

[andreybokhanko]

In D18035#450247, @hfinkel wrote:

The link was posted here: http://sourcerytools.com/pipermail/cxx-abi-dev/2016-June/002919.html - which is the mailing list where the C++ ABI specification is discussed.

Ah, I see... Dmitry told me that this one is not terribly detailed, and you revealed the C++ meeting episode after posting the link -- that's why I thought there is another ("real" :-)) one available. I stand corrected.

Sorry if my message offended you -- knowing you, I just couldn't believe you are not sharing a spec you have. Turns out I was right! :-)

Yours,
Andrey

[DmitryPolukhin]

In D18035#450258, @rsmith wrote:

Yes, I definitely want us to implement this for GCC compatibility. And now that we have a specification for this feature, we can evaluate whether this is doing the right thing. On that basis:

I still want this refactored so that the normally-mangled part of a function name is only mangled once, rather than being mangled twice (once to find the implicit tag set and once to actually produce the mangled name). As suggested, you can achieve this by first computing the set of tags from the return type, then mangling the encoding to a separate buffer (collecting tags as you go) if the set is non-empty, and finally writing any remaining tags and the buffer contents.

Please factor out a function to mangle the source name and ABI tags for a NamedDecl rather than duplicating that pair of calls throughout the patch.

Current discussion on the ABI list suggests that it is not correct to mangle the return type / variable type to get the implicit tag set. The set of available attributes should be determined by a recursive walk of the original type (prior to any substitution), not by mangling it and seeing what it references. It's not yet clear whether that's the actual design intent or just the emergent behavior of the GCC implementation, however.

I'm monitoring the discussion and will try to rewrite this patch according to the guidance and avoid double mangling.

[DmitryPolukhin]

This patch set contains serious refactoring to make it closer to what Richard suggested. Unfortunately there is no way to fully implement Richard's idea because we have to mangle twice name of functions and variables. But this patch reuse mangled bare function type generated during tags calculation.

NOTE for people who use this patch for local testing: this patch set was not tested extensively on real world apps so it might have be worse than previous one. If you can, please test it in your environment and report any issues. For now "stable" version of this patch is previous patch set from May 23.

Richard, please take a look and let me know if it looks better for you. IMHO, it becomes smaller and simpler and reuse mangling for function prototype.

[DmitryPolukhin]

• removed wrong asserts that I used for an experiment

[DmitryPolukhin]

Fixed issue with substitution from function name used in bare type encoding and added test. With this patch Clang passes self build with GCC 5.3.1 headers and C++ libraries so it gives some level of confidence that it works on real apps.

PTAL!

[rsmith]

Thank you! I'm happy with this implementation (other than some data structure improvements), and cxx-abi-dev discussion seems to be settling on this approach (mangling the return type / variable type to extract attributes) being the right one.

(Minor nit: please make sure that your comments start with a capital letter and end in a period.)

lib/AST/ItaniumMangle.cpp

352–355

You're going to sort the result list anyway, so how about adding the tag here without checking if it's already present, then using std::unique to weed out duplicates after you sort?

679–683

Instead of keeping the UsedAbiTags as a SmallSetVector, you can just keep a SmallVector of them, and sort/unique it here. Since you keep the list of emitted ABI tags sorted, you can then use std::set_difference to extract the additional tags in linear time.

[DmitryPolukhin]

Use SmallVector instead of SmallSetVector and sort the vector when needed.

[rsmith]

LGTM, thank you so much for your patience and hard work on this change!

[DmitryPolukhin]

Richard, thank you for the review!

I decided to commit this patch without waiting for GCC response to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71712 (that is last compatibility issues in comparison with GCC6) so more people could test Clang implementation of ABI tags on real apps and report issues if any. All, please let me know (file bug and add me in CC) if you observe any issues with abi_tag implementation in Clang.

lib/AST/ItaniumMangle.cpp

public:
   }
   /// @}
 };
 
 /// Manage the mangling of a single name.
 class CXXNameMangler {
   ItaniumMangleContextImpl &Context;
   raw_ostream &Out;
+  bool NullOut = false;
+  /// In the "DisableDerivedAbiTags" mode derived ABI tags are not calculated.
+  /// This mode is used when mangler creates another mangler recursively to
+  /// calculate ABI tags for the function return value or the variable type.
+  /// Also it is required to avoid infinite recursion in some cases.
+  bool DisableDerivedAbiTags = false;
 
   /// The "structor" is the top-level declaration being mangled, if
   /// that's not a template specialization; otherwise it's the pattern
   /// for that specialization.
   const NamedDecl *Structor;
   unsigned StructorType;
 
   /// The next substitution sequence number.
public:
 
     void pop(FunctionTypeDepthState saved) {
       assert(getDepth() == saved.getDepth() + 1);
       Bits = saved.Bits;
     }
 
   } FunctionTypeDepth;
 
+  // abi_tag is a gcc attribute, taking one or more strings called "tags".
+  // The goal is to annotate against which version of a library an object was
+  // built and to be able to provide backwards compatibility ("dual abi").
+  // For more information see docs/ItaniumMangleAbiTags.rst.
+  typedef SmallVector<StringRef, 4> AbiTagList;
+  typedef llvm::SmallSetVector<StringRef, 4> AbiTagSet;
+
+  // State to gather all implicit and explicit tags used in a mangled name.
+  // Must always have an instance of this while emitting any name to keep
+  // track.
+  class AbiTagState final {
+    //! All abi tags used implicitly or explicitly
+    AbiTagSet UsedAbiTags;
+    //! All explicit abi tags (i.e. not from namespace)
+    AbiTagSet EmittedAbiTags;
+
+    AbiTagState *&LinkHead;
+    AbiTagState *Parent = nullptr;
+
+    bool LinkActive = false;
+
+  public:
+    explicit AbiTagState(AbiTagState *&Head) : LinkHead(Head) {
+      Parent = LinkHead;
+      LinkHead = this;
+      LinkActive = true;
+    }
+
+    // no copy, no move
+    AbiTagState(const AbiTagState &) = delete;
+    AbiTagState &operator=(const AbiTagState &) = delete;
+
+    ~AbiTagState() { pop(); }
+
+    void pop() {
+      if (!LinkActive)
+        return;
+
+      assert(LinkHead == this &&
+             "abi tag link head must point to us on destruction");
+      LinkActive = false;
+      if (Parent) {
+        Parent->UsedAbiTags.insert(UsedAbiTags.begin(), UsedAbiTags.end());
+        Parent->EmittedAbiTags.insert(EmittedAbiTags.begin(),
+                                      EmittedAbiTags.end());
+      }
+      LinkHead = Parent;
+    }
+
+    void write(raw_ostream &Out, const NamedDecl *ND,
+               const AbiTagList *AdditionalAbiTags) {
+      ND = cast<NamedDecl>(ND->getCanonicalDecl());
+
+      if (!isa<FunctionDecl>(ND) && !isa<VarDecl>(ND)) {
+        assert(
+            !AdditionalAbiTags &&
+            "only function and variables need a list of additional abi tags");
+        if (const auto *NS = dyn_cast<NamespaceDecl>(ND)) {
+          if (const auto *AbiTag = NS->getAttr<AbiTagAttr>()) {
+            for (const auto &Tag : AbiTag->tags()) {
+              UsedAbiTags.insert(Tag);
+            }
+          }
+          // Don't emit abi tags for namespaces.
+          return;
+        }
+      }
+
+      AbiTagList TagList;
+      if (const auto *AbiTag = ND->getAttr<AbiTagAttr>()) {
+        for (const auto &Tag : AbiTag->tags()) {
+          UsedAbiTags.insert(Tag);
+          // AbiTag->tags() is sorted and has no duplicates
+          TagList.push_back(Tag);
+        }
+      }
+
+      if (AdditionalAbiTags) {
+        for (const auto &Tag : *AdditionalAbiTags) {
+          UsedAbiTags.insert(Tag);
+          if (std::find(TagList.begin(), TagList.end(), Tag) == TagList.end()) {
+            // don't insert duplicates
+            TagList.push_back(Tag);
+          }
+        }
+        // AbiTag->tags() are already sorted; only add if we had additional tags
+        std::sort(TagList.begin(), TagList.end());
+      }
+
+      writeSortedUniqueAbiTags(Out, TagList);
+    }
+
+    const AbiTagSet &getUsedAbiTags() const { return UsedAbiTags; }
+    void setUsedAbiTags(const AbiTagSet &AbiTags) {
+      UsedAbiTags = AbiTags;
+    }
+
+    const AbiTagSet &getEmittedAbiTags() const {
+      return EmittedAbiTags;
+    }
+
+  private:
+    template <typename TagList>
+    void writeSortedUniqueAbiTags(raw_ostream &Out, TagList const &AbiTags) {
+      for (const auto &Tag : AbiTags) {
+        EmittedAbiTags.insert(Tag);
+        Out << "B";
+        Out << Tag.size();
+        Out << Tag;
+      }
+    }
+  };
+
+  AbiTagState *AbiTags = nullptr;
+  AbiTagState AbiTagsRoot;
+
   llvm::DenseMap<uintptr_t, unsigned> Substitutions;
 
   ASTContext &getASTContext() const { return Context.getASTContext(); }
 
 public:
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
-                 const NamedDecl *D = nullptr)
-    : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(0),
-      SeqID(0) {
+                 const NamedDecl *D = nullptr, bool NullOut_ = false)
+    : Context(C), Out(Out_), NullOut(NullOut_),  Structor(getStructor(D)),
+      StructorType(0), SeqID(0), AbiTagsRoot(AbiTags) {
     // These can't be mangled without a ctor type or dtor type.
     assert(!D || (!isa<CXXDestructorDecl>(D) &&
                   !isa<CXXConstructorDecl>(D)));
   }
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                  const CXXConstructorDecl *D, CXXCtorType Type)
     : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
-      SeqID(0) { }
+      SeqID(0), AbiTagsRoot(AbiTags) { }
   CXXNameMangler(ItaniumMangleContextImpl &C, raw_ostream &Out_,
                  const CXXDestructorDecl *D, CXXDtorType Type)
     : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
-      SeqID(0) { }
+      SeqID(0), AbiTagsRoot(AbiTags) { }
+
+  CXXNameMangler(CXXNameMangler &Outer, raw_ostream &Out_)
+      : Context(Outer.Context), Out(Out_), NullOut(false),
+        Structor(Outer.Structor), StructorType(Outer.StructorType),
+        SeqID(Outer.SeqID), AbiTagsRoot(AbiTags) {}
+
+  CXXNameMangler(CXXNameMangler &Outer, llvm::raw_null_ostream &Out_)
+      : Context(Outer.Context), Out(Out_), NullOut(true),
+        Structor(Outer.Structor), StructorType(Outer.StructorType),
+        SeqID(Outer.SeqID), AbiTagsRoot(AbiTags) {}
 
 #if MANGLE_CHECKER
   ~CXXNameMangler() {
     if (Out.str()[0] == '\01')
       return;
 
     int status = 0;
     char *result = abi::__cxa_demangle(Out.str().str().c_str(), 0, 0, &status);
     assert(status == 0 && "Could not demangle mangled name!");
     free(result);
   }
 #endif
   raw_ostream &getStream() { return Out; }
 
+  void disableDerivedAbiTags() { DisableDerivedAbiTags = true; }
+  static bool shouldHaveAbiTags(ItaniumMangleContextImpl &C, const VarDecl *VD);
+
   void mangle(const NamedDecl *D);
   void mangleCallOffset(int64_t NonVirtual, int64_t Virtual);
   void mangleNumber(const llvm::APSInt &I);
   void mangleNumber(int64_t Number);
   void mangleFloat(const llvm::APFloat &F);
   void mangleFunctionEncoding(const FunctionDecl *FD);
   void mangleSeqID(unsigned SeqID);
   void mangleName(const NamedDecl *ND);
private:
   void addSubstitution(uintptr_t Ptr);
 
   void mangleUnresolvedPrefix(NestedNameSpecifier *qualifier,
                               bool recursive = false);
   void mangleUnresolvedName(NestedNameSpecifier *qualifier,
                             DeclarationName name,
                             unsigned KnownArity = UnknownArity);
 
-  void mangleName(const TemplateDecl *TD,
+  void mangleFunctionEncodingBareType(const FunctionDecl *FD);
+
+  void mangleNameWithAbiTags(const NamedDecl *ND,
+                             const AbiTagList *AdditionalAbiTags);
+  void mangleTemplateName(const TemplateDecl *TD,
                           const TemplateArgument *TemplateArgs,
                           unsigned NumTemplateArgs);
-  void mangleUnqualifiedName(const NamedDecl *ND) {
-    mangleUnqualifiedName(ND, ND->getDeclName(), UnknownArity);
+  void mangleUnqualifiedName(const NamedDecl *ND,
+                             const AbiTagList *AdditionalAbiTags) {
+    mangleUnqualifiedName(ND, ND->getDeclName(), UnknownArity,
+                          AdditionalAbiTags);
   }
   void mangleUnqualifiedName(const NamedDecl *ND, DeclarationName Name,
-                             unsigned KnownArity);
-  void mangleUnscopedName(const NamedDecl *ND);
-  void mangleUnscopedTemplateName(const TemplateDecl *ND);
-  void mangleUnscopedTemplateName(TemplateName);
+                             unsigned KnownArity,
+                             const AbiTagList *AdditionalAbiTags);
+  void mangleUnscopedName(const NamedDecl *ND,
+                          const AbiTagList *AdditionalAbiTags);
+  void mangleUnscopedTemplateName(const TemplateDecl *ND,
+                                  const AbiTagList *AdditionalAbiTags);
+  void mangleUnscopedTemplateName(TemplateName,
+                                  const AbiTagList *AdditionalAbiTags);
   void mangleSourceName(const IdentifierInfo *II);
-  void mangleLocalName(const Decl *D);
+  void mangleSourceNameWithAbiTags(
+      const NamedDecl *ND, const AbiTagList *AdditionalAbiTags = nullptr);
+  void mangleLocalName(const Decl *D,
+                       const AbiTagList *AdditionalAbiTags);
   void mangleBlockForPrefix(const BlockDecl *Block);
   void mangleUnqualifiedBlock(const BlockDecl *Block);
   void mangleLambda(const CXXRecordDecl *Lambda);
   void mangleNestedName(const NamedDecl *ND, const DeclContext *DC,
+                        const AbiTagList *AdditionalAbiTags,
                         bool NoFunction=false);
   void mangleNestedName(const TemplateDecl *TD,
                         const TemplateArgument *TemplateArgs,
                         unsigned NumTemplateArgs);
   void manglePrefix(NestedNameSpecifier *qualifier);
   void manglePrefix(const DeclContext *DC, bool NoFunction=false);
   void manglePrefix(QualType type);
   void mangleTemplatePrefix(const TemplateDecl *ND, bool NoFunction=false);
#include "clang/AST/TypeNodes.def"
   void mangleTemplateArgs(const TemplateArgument *TemplateArgs,
                           unsigned NumTemplateArgs);
   void mangleTemplateArgs(const TemplateArgumentList &AL);
   void mangleTemplateArg(TemplateArgument A);
 
   void mangleTemplateParameter(unsigned Index);
 
   void mangleFunctionParam(const ParmVarDecl *parm);
+
+  void writeAbiTags(const NamedDecl *ND,
+                    const AbiTagList *AdditionalAbiTags);
+
+  AbiTagSet makeFunctionReturnTypeTags(const FunctionDecl *FD);
+  AbiTagSet makeVariableTypeTags(const VarDecl *VD);
 };
 
 }
 
 bool ItaniumMangleContextImpl::shouldMangleCXXName(const NamedDecl *D) {
   const FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
   if (FD) {
     LanguageLinkage L = FD->getLanguageLinkage();
if (VD) {
 
     // Variables at global scope with non-internal linkage are not mangled
     const DeclContext *DC = getEffectiveDeclContext(D);
     // Check for extern variable declared locally.
     if (DC->isFunctionOrMethod() && D->hasLinkage())
       while (!DC->isNamespace() && !DC->isTranslationUnit())
         DC = getEffectiveParentContext(DC);
     if (DC->isTranslationUnit() && D->getFormalLinkage() != InternalLinkage &&
+        !CXXNameMangler::shouldHaveAbiTags(*this, VD) &&
         !isa<VarTemplateSpecializationDecl>(D))
       return false;
   }
 
   return true;
 }
 
+void CXXNameMangler::writeAbiTags(const NamedDecl *ND,
+                                  const AbiTagList *AdditionalAbiTags) {
+  assert(AbiTags && "require AbiTagState");
+  AbiTags->write(Out, ND, DisableDerivedAbiTags ? nullptr : AdditionalAbiTags);
+}
+
+void CXXNameMangler::mangleSourceNameWithAbiTags(
+    const NamedDecl *ND, const AbiTagList *AdditionalAbiTags) {
+  mangleSourceName(ND->getIdentifier());
+  writeAbiTags(ND, AdditionalAbiTags);
+}
+
 void CXXNameMangler::mangle(const NamedDecl *D) {
   // <mangled-name> ::= _Z <encoding>
   //            ::= <data name>
   //            ::= <special-name>
   Out << "_Z";
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
     mangleFunctionEncoding(FD);
   else if (const VarDecl *VD = dyn_cast<VarDecl>(D))
     mangleName(VD);
   else if (const IndirectFieldDecl *IFD = dyn_cast<IndirectFieldDecl>(D))
     mangleName(IFD->getAnonField());
   else
     mangleName(cast<FieldDecl>(D));
 }
 
 void CXXNameMangler::mangleFunctionEncoding(const FunctionDecl *FD) {
   // <encoding> ::= <function name> <bare-function-type>
-  mangleName(FD);
 
   // Don't mangle in the type if this isn't a decl we should typically mangle.
-  if (!Context.shouldMangleDeclName(FD))
+  if (!Context.shouldMangleDeclName(FD)) {
+    mangleName(FD);
+    return;
+  }
+
+  AbiTagSet ReturnTypeAbiTags = makeFunctionReturnTypeTags(FD);
+  if (ReturnTypeAbiTags.empty()) {
+    // There are no tags for return type, the simplest case.
+    mangleName(FD);
+    mangleFunctionEncodingBareType(FD);
     return;
+  }
+
+  // Mangle function encoding to temporary buffer.
+  SmallString<256> FunctionEncodingBuf;
+  llvm::raw_svector_ostream FunctionEncodingStream(FunctionEncodingBuf);
+  CXXNameMangler FunctionEncodingMangler(*this, FunctionEncodingStream);
+  FunctionEncodingMangler.mangleFunctionEncodingBareType(FD);
+
+  // Mangle function name to null stream to collect tags.
+  llvm::raw_null_ostream NullOutStream;
+  CXXNameMangler FunctionNameMangler(*this, NullOutStream);
+  FunctionNameMangler.disableDerivedAbiTags();
+  FunctionNameMangler.mangleNameWithAbiTags(FD, nullptr);
+
+  // Get tags from return type that are not present in function name or encoding
+  AbiTagList AdditionalAbiTags;
+  for (const auto &Tag : ReturnTypeAbiTags) {
+    if (!FunctionEncodingMangler.AbiTagsRoot.getUsedAbiTags().count(Tag) &&
+        !FunctionNameMangler.AbiTagsRoot.getUsedAbiTags().count(Tag))
+      AdditionalAbiTags.push_back(Tag);
+  }
+
+  // Output name with implicit tags and function encoding from temporary buffer.
+  mangleNameWithAbiTags(FD, &AdditionalAbiTags);
+  Out << FunctionEncodingStream.str();
+}
 
+void CXXNameMangler::mangleFunctionEncodingBareType(const FunctionDecl *FD) {
   if (FD->hasAttr<EnableIfAttr>()) {
     FunctionTypeDepthState Saved = FunctionTypeDepth.push();
     Out << "Ua9enable_ifI";
     // FIXME: specific_attr_iterator iterates in reverse order. Fix that and use
     // it here.
     for (AttrVec::const_reverse_iterator I = FD->getAttrs().rbegin(),
                                          E = FD->getAttrs().rend();
          I != E; ++I) {
if (const VarTemplateSpecializationDecl *Spec =
     TemplateArgs = &Spec->getTemplateArgs();
     return Spec->getSpecializedTemplate();
   }
 
   return nullptr;
 }
 
 void CXXNameMangler::mangleName(const NamedDecl *ND) {
+  if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
+    // Variables should have implicit tags from its type.
+    AbiTagSet VariableTypeAbiTags = makeVariableTypeTags(VD);
+    if (VariableTypeAbiTags.empty()) {
+      // Simple case no variable type tags.
+      mangleNameWithAbiTags(VD, nullptr);
+      return;
+    }
+
+    // Mangle variable name to null stream to collect tags.
+    llvm::raw_null_ostream NullOutStream;
+    CXXNameMangler VariableNameMangler(*this, NullOutStream);
+    VariableNameMangler.disableDerivedAbiTags();
+    VariableNameMangler.mangleNameWithAbiTags(VD, nullptr);
+
+    // Get tags from variable type that are not present in its name.
+    AbiTagList AdditionalAbiTags;
+    for (const auto &Tag : VariableTypeAbiTags) {
+     if (!VariableNameMangler.AbiTagsRoot.getUsedAbiTags().count(Tag))
+        AdditionalAbiTags.push_back(Tag);
+    }
+
+    // Output name with implicit tags.
+    mangleNameWithAbiTags(VD, &AdditionalAbiTags);
+  } else {
+    mangleNameWithAbiTags(ND, nullptr);
+  }
+}
+
+void CXXNameMangler::mangleNameWithAbiTags(const NamedDecl *ND,
+                                           const AbiTagList *AdditionalAbiTags) {
   //  <name> ::= <nested-name>
   //         ::= <unscoped-name>
   //         ::= <unscoped-template-name> <template-args>
   //         ::= <local-name>
   //
   const DeclContext *DC = getEffectiveDeclContext(ND);
 
   // If this is an extern variable declared locally, the relevant DeclContext
   // is that of the containing namespace, or the translation unit.
   // FIXME: This is a hack; extern variables declared locally should have
   // a proper semantic declaration context!
   if (isLocalContainerContext(DC) && ND->hasLinkage() && !isLambda(ND))
     while (!DC->isNamespace() && !DC->isTranslationUnit())
       DC = getEffectiveParentContext(DC);
   else if (GetLocalClassDecl(ND)) {
-    mangleLocalName(ND);
+    mangleLocalName(ND, AdditionalAbiTags);
     return;
   }
 
   DC = IgnoreLinkageSpecDecls(DC);
 
   if (DC->isTranslationUnit() || isStdNamespace(DC)) {
     // Check if we have a template.
     const TemplateArgumentList *TemplateArgs = nullptr;
     if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
-      mangleUnscopedTemplateName(TD);
+      mangleUnscopedTemplateName(TD, AdditionalAbiTags);
       mangleTemplateArgs(*TemplateArgs);
       return;
     }
 
-    mangleUnscopedName(ND);
+    mangleUnscopedName(ND, AdditionalAbiTags);
     return;
   }
 
   if (isLocalContainerContext(DC)) {
-    mangleLocalName(ND);
+    mangleLocalName(ND, AdditionalAbiTags);
     return;
   }
 
-  mangleNestedName(ND, DC);
+  mangleNestedName(ND, DC, AdditionalAbiTags);
 }
-void CXXNameMangler::mangleName(const TemplateDecl *TD,
+
+void CXXNameMangler::mangleTemplateName(const TemplateDecl *TD,
                                         const TemplateArgument *TemplateArgs,
                                         unsigned NumTemplateArgs) {
   const DeclContext *DC = IgnoreLinkageSpecDecls(getEffectiveDeclContext(TD));
 
   if (DC->isTranslationUnit() || isStdNamespace(DC)) {
-    mangleUnscopedTemplateName(TD);
+    mangleUnscopedTemplateName(TD, nullptr);
     mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
   } else {
     mangleNestedName(TD, TemplateArgs, NumTemplateArgs);
   }
 }
 
-void CXXNameMangler::mangleUnscopedName(const NamedDecl *ND) {
+void CXXNameMangler::mangleUnscopedName(const NamedDecl *ND,
+                                        const AbiTagList *AdditionalAbiTags) {
   //  <unscoped-name> ::= <unqualified-name>
   //                  ::= St <unqualified-name>   # ::std::
 
   if (isStdNamespace(IgnoreLinkageSpecDecls(getEffectiveDeclContext(ND))))
     Out << "St";
 
-  mangleUnqualifiedName(ND);
+  mangleUnqualifiedName(ND, AdditionalAbiTags);
 }
 
-void CXXNameMangler::mangleUnscopedTemplateName(const TemplateDecl *ND) {
+void CXXNameMangler::mangleUnscopedTemplateName(
+    const TemplateDecl *ND, const AbiTagList *AdditionalAbiTags) {
+  assert(!AdditionalAbiTags || AdditionalAbiTags->empty());
   //     <unscoped-template-name> ::= <unscoped-name>
   //                              ::= <substitution>
   if (mangleSubstitution(ND))
     return;
 
   // <template-template-param> ::= <template-param>
-  if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND))
+  if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
+    assert(!AdditionalAbiTags &&
+           "template template param cannot have abi tags");
     mangleTemplateParameter(TTP->getIndex());
-  else
-    mangleUnscopedName(ND->getTemplatedDecl());
+  } else {
+    mangleUnscopedName(ND->getTemplatedDecl(), AdditionalAbiTags);
+  }
 
   addSubstitution(ND);
 }
 
-void CXXNameMangler::mangleUnscopedTemplateName(TemplateName Template) {
+void CXXNameMangler::mangleUnscopedTemplateName(
+    TemplateName Template, const AbiTagList *AdditionalAbiTags) {
+  assert(!AdditionalAbiTags || AdditionalAbiTags->empty());
   //     <unscoped-template-name> ::= <unscoped-name>
   //                              ::= <substitution>
   if (TemplateDecl *TD = Template.getAsTemplateDecl())
-    return mangleUnscopedTemplateName(TD);
+    return mangleUnscopedTemplateName(TD, AdditionalAbiTags);
   
   if (mangleSubstitution(Template))
     return;
 
+  assert(!AdditionalAbiTags &&
+         "dependent template name cannot have abi tags");
+
   DependentTemplateName *Dependent = Template.getAsDependentTemplateName();
   assert(Dependent && "Not a dependent template name?");
   if (const IdentifierInfo *Id = Dependent->getIdentifier())
     mangleSourceName(Id);
   else
     mangleOperatorName(Dependent->getOperator(), UnknownArity);
-  
   addSubstitution(Template);
 }
 
 void CXXNameMangler::mangleFloat(const llvm::APFloat &f) {
   // ABI:
   //   Floating-point literals are encoded using a fixed-length
   //   lowercase hexadecimal string corresponding to the internal
   //   representation (IEEE on Itanium), high-order bytes first,
case NestedNameSpecifier::Super:
     llvm_unreachable("Can't mangle __super specifier");
 
   case NestedNameSpecifier::Namespace:
     if (qualifier->getPrefix())
       mangleUnresolvedPrefix(qualifier->getPrefix(),
                              /*recursive*/ true);
     else
       Out << "sr";
-    mangleSourceName(qualifier->getAsNamespace()->getIdentifier());
+    mangleSourceNameWithAbiTags(qualifier->getAsNamespace());
     break;
   case NestedNameSpecifier::NamespaceAlias:
     if (qualifier->getPrefix())
       mangleUnresolvedPrefix(qualifier->getPrefix(),
                              /*recursive*/ true);
     else
       Out << "sr";
-    mangleSourceName(qualifier->getAsNamespaceAlias()->getIdentifier());
+    mangleSourceNameWithAbiTags(qualifier->getAsNamespaceAlias());
     break;
 
   case NestedNameSpecifier::TypeSpec:
   case NestedNameSpecifier::TypeSpecWithTemplate: {
     const Type *type = qualifier->getAsType();
 
     // We only want to use an unresolved-type encoding if this is one of:
     //   - a decltype
case NestedNameSpecifier::Identifier:
     // Member expressions can have these without prefixes.
     if (qualifier->getPrefix())
       mangleUnresolvedPrefix(qualifier->getPrefix(),
                              /*recursive*/ true);
     else
       Out << "sr";
 
     mangleSourceName(qualifier->getAsIdentifier());
+    // an Identifier has no type information, so we can't emit abi tags for it
     break;
   }
 
   // If this was the innermost part of the NNS, and we fell out to
   // here, append an 'E'.
   if (!recursive)
     Out << 'E';
 }
switch (name.getNameKind()) {
     case DeclarationName::ObjCOneArgSelector:
     case DeclarationName::ObjCZeroArgSelector:
       llvm_unreachable("Can't mangle Objective-C selector names here!");
   }
 }
 
 void CXXNameMangler::mangleUnqualifiedName(const NamedDecl *ND,
                                            DeclarationName Name,
-                                           unsigned KnownArity) {
+                                           unsigned KnownArity,
+                                           const AbiTagList *AdditionalAbiTags) {
   unsigned Arity = KnownArity;
   //  <unqualified-name> ::= <operator-name>
   //                     ::= <ctor-dtor-name>
   //                     ::= <source-name>
   switch (Name.getNameKind()) {
   case DeclarationName::Identifier: {
     if (const IdentifierInfo *II = Name.getAsIdentifierInfo()) {
       // We must avoid conflicts between internally- and externally-
       // linked variable and function declaration names in the same TU:
       //   void test() { extern void foo(); }
       //   static void foo();
       // This naming convention is the same as that followed by GCC,
       // though it shouldn't actually matter.
       if (ND && ND->getFormalLinkage() == InternalLinkage &&
           getEffectiveDeclContext(ND)->isFileContext())
         Out << 'L';
 
       mangleSourceName(II);
+      writeAbiTags(ND, AdditionalAbiTags);
       break;
     }
 
     // Otherwise, an anonymous entity.  We must have a declaration.
     assert(ND && "mangling empty name without declaration");
 
     if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
       if (NS->isAnonymousNamespace()) {
if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
 
       // It's actually possible for various reasons for us to get here
       // with an empty anonymous struct / union.  Fortunately, it
       // doesn't really matter what name we generate.
       if (!FD) break;
       assert(FD->getIdentifier() && "Data member name isn't an identifier!");
 
       mangleSourceName(FD->getIdentifier());
+      // Not emitting abi tags: internal name anyway
       break;
     }
 
     // Class extensions have no name as a category, and it's possible
     // for them to be the semantic parent of certain declarations
     // (primarily, tag decls defined within declarations).  Such
     // declarations will always have internal linkage, so the name
     // doesn't really matter, but we shouldn't crash on them.  For
     // safety, just handle all ObjC containers here.
     if (isa<ObjCContainerDecl>(ND))
       break;
     
     // We must have an anonymous struct.
     const TagDecl *TD = cast<TagDecl>(ND);
     if (const TypedefNameDecl *D = TD->getTypedefNameForAnonDecl()) {
       assert(TD->getDeclContext() == D->getDeclContext() &&
              "Typedef should not be in another decl context!");
       assert(D->getDeclName().getAsIdentifierInfo() &&
              "Typedef was not named!");
       mangleSourceName(D->getDeclName().getAsIdentifierInfo());
+      assert(!AdditionalAbiTags && "Type cannot have additional abi tags");
+      // explicit abi tags are still possible; take from underlying type, not
+      // from typedef.
+      writeAbiTags(TD, nullptr);
       break;
     }
 
     // <unnamed-type-name> ::= <closure-type-name>
     // 
     // <closure-type-name> ::= Ul <lambda-sig> E [ <nonnegative number> ] _
     // <lambda-sig> ::= <parameter-type>+   # Parameter types or 'v' for 'void'.
     if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(TD)) {
       if (Record->isLambda() && Record->getLambdaManglingNumber()) {
+        assert(!AdditionalAbiTags &&
+               "Lambda type cannot have additional abi tags");
         mangleLambda(Record);
         break;
       }
     }
 
     if (TD->isExternallyVisible()) {
       unsigned UnnamedMangle = getASTContext().getManglingNumber(TD);
       Out << "Ut";
       if (UnnamedMangle > 1)
         Out << UnnamedMangle - 2;
       Out << '_';
+      writeAbiTags(TD, AdditionalAbiTags);
       break;
     }
 
-    // Get a unique id for the anonymous struct.
-    unsigned AnonStructId = Context.getAnonymousStructId(TD);
+    // Get a unique id for the anonymous struct. If it is not a real output
+    // ID doesn't matter so use fake one.
+    unsigned AnonStructId = NullOut ? 0 : Context.getAnonymousStructId(TD);
 
     // Mangle it as a source name in the form
     // [n] $_<id>
     // where n is the length of the string.
     SmallString<8> Str;
     Str += "$_";
     Str += llvm::utostr(AnonStructId);
 
case DeclarationName::CXXConstructorName:
     if (ND == Structor)
       // If the named decl is the C++ constructor we're mangling, use the type
       // we were given.
       mangleCXXCtorType(static_cast<CXXCtorType>(StructorType));
     else
       // Otherwise, use the complete constructor name. This is relevant if a
       // class with a constructor is declared within a constructor.
       mangleCXXCtorType(Ctor_Complete);
+    writeAbiTags(ND, AdditionalAbiTags);
     break;
 
   case DeclarationName::CXXDestructorName:
     if (ND == Structor)
       // If the named decl is the C++ destructor we're mangling, use the type we
       // were given.
       mangleCXXDtorType(static_cast<CXXDtorType>(StructorType));
     else
       // Otherwise, use the complete destructor name. This is relevant if a
       // class with a destructor is declared within a destructor.
       mangleCXXDtorType(Dtor_Complete);
+    writeAbiTags(ND, AdditionalAbiTags);
     break;
 
   case DeclarationName::CXXOperatorName:
     if (ND && Arity == UnknownArity) {
       Arity = cast<FunctionDecl>(ND)->getNumParams();
 
       // If we have a member function, we need to include the 'this' pointer.
       if (const auto *MD = dyn_cast<CXXMethodDecl>(ND))
         if (!MD->isStatic())
           Arity++;
     }
   // FALLTHROUGH
   case DeclarationName::CXXConversionFunctionName:
   case DeclarationName::CXXLiteralOperatorName:
     mangleOperatorName(Name, Arity);
+    writeAbiTags(ND, AdditionalAbiTags);
     break;
 
   case DeclarationName::CXXUsingDirective:
     llvm_unreachable("Can't mangle a using directive name!");
   }
 }
 
 void CXXNameMangler::mangleSourceName(const IdentifierInfo *II) {
   // <source-name> ::= <positive length number> <identifier>
   // <number> ::= [n] <non-negative decimal integer>
   // <identifier> ::= <unqualified source code identifier>
   Out << II->getLength() << II->getName();
 }
 
 void CXXNameMangler::mangleNestedName(const NamedDecl *ND,
                                       const DeclContext *DC,
+                                      const AbiTagList *AdditionalAbiTags,
                                       bool NoFunction) {
   // <nested-name> 
   //   ::= N [<CV-qualifiers>] [<ref-qualifier>] <prefix> <unqualified-name> E
   //   ::= N [<CV-qualifiers>] [<ref-qualifier>] <template-prefix> 
   //       <template-args> E
 
   Out << 'N';
   if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(ND)) {
void CXXNameMangler::mangleNestedName(const NamedDecl *ND,
   // Check if we have a template.
   const TemplateArgumentList *TemplateArgs = nullptr;
   if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
     mangleTemplatePrefix(TD, NoFunction);
     mangleTemplateArgs(*TemplateArgs);
   }
   else {
     manglePrefix(DC, NoFunction);
-    mangleUnqualifiedName(ND);
+    mangleUnqualifiedName(ND, AdditionalAbiTags);
   }
 
   Out << 'E';
 }
 void CXXNameMangler::mangleNestedName(const TemplateDecl *TD,
                                       const TemplateArgument *TemplateArgs,
                                       unsigned NumTemplateArgs) {
   // <nested-name> ::= N [<CV-qualifiers>] <template-prefix> <template-args> E
 
   Out << 'N';
 
   mangleTemplatePrefix(TD);
   mangleTemplateArgs(TemplateArgs, NumTemplateArgs);
 
   Out << 'E';
 }
 
-void CXXNameMangler::mangleLocalName(const Decl *D) {
+void CXXNameMangler::mangleLocalName(const Decl *D,
+                                     const AbiTagList *AdditionalAbiTags) {
   // <local-name> := Z <function encoding> E <entity name> [<discriminator>]
   //              := Z <function encoding> E s [<discriminator>]
   // <local-name> := Z <function encoding> E d [ <parameter number> ] 
   //                 _ <entity name>
   // <discriminator> := _ <non-negative number>
   assert(isa<NamedDecl>(D) || isa<BlockDecl>(D));
   const RecordDecl *RD = GetLocalClassDecl(D);
   const DeclContext *DC = getEffectiveDeclContext(RD ? RD : D);
 
   Out << 'Z';
 
+  {
+    AbiTagState LocalAbiTags(AbiTags);
+
     if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(DC))
       mangleObjCMethodName(MD);
     else if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC))
       mangleBlockForPrefix(BD);
     else
       mangleFunctionEncoding(cast<FunctionDecl>(DC));
 
+    // Implicit ABI tags (from namespace) are not available in the following
+    // entity; reset to actually emitted tags, which are available.
+    LocalAbiTags.setUsedAbiTags(LocalAbiTags.getEmittedAbiTags());
+  }
+
   Out << 'E';
 
+  // GCC 5.3.0 doesn't emit derived ABI tags for local names but that seems to
+  // be a bug that is fixed in trunk.
+
   if (RD) {
     // The parameter number is omitted for the last parameter, 0 for the 
     // second-to-last parameter, 1 for the third-to-last parameter, etc. The 
     // <entity name> will of course contain a <closure-type-name>: Its 
     // numbering will be local to the particular argument in which it appears
     // -- other default arguments do not affect its encoding.
     const CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(RD);
     if (CXXRD->isLambda()) {
       if (const ParmVarDecl *Parm
               = dyn_cast_or_null<ParmVarDecl>(CXXRD->getLambdaContextDecl())) {
         if (const FunctionDecl *Func
               = dyn_cast<FunctionDecl>(Parm->getDeclContext())) {
           Out << 'd';
           unsigned Num = Func->getNumParams() - Parm->getFunctionScopeIndex();
           if (Num > 1)
             mangleNumber(Num - 2);
           Out << '_';
         }
       }
     }
     
     // Mangle the name relative to the closest enclosing function.
     // equality ok because RD derived from ND above
     if (D == RD)  {
-      mangleUnqualifiedName(RD);
+      mangleUnqualifiedName(RD, AdditionalAbiTags);
     } else if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
       manglePrefix(getEffectiveDeclContext(BD), true /*NoFunction*/);
+      assert(!AdditionalAbiTags && "Block cannot have additional abi tags");
       mangleUnqualifiedBlock(BD);
     } else {
       const NamedDecl *ND = cast<NamedDecl>(D);
-      mangleNestedName(ND, getEffectiveDeclContext(ND), true /*NoFunction*/);
+      mangleNestedName(ND, getEffectiveDeclContext(ND), AdditionalAbiTags,
+                       true /*NoFunction*/);
     }
   } else if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
     // Mangle a block in a default parameter; see above explanation for
     // lambdas.
     if (const ParmVarDecl *Parm
             = dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl())) {
       if (const FunctionDecl *Func
             = dyn_cast<FunctionDecl>(Parm->getDeclContext())) {
         Out << 'd';
         unsigned Num = Func->getNumParams() - Parm->getFunctionScopeIndex();
         if (Num > 1)
           mangleNumber(Num - 2);
         Out << '_';
       }
     }
 
+    assert(!AdditionalAbiTags && "Block cannot have additional abi tags");
     mangleUnqualifiedBlock(BD);
   } else {
-    mangleUnqualifiedName(cast<NamedDecl>(D));
+    mangleUnqualifiedName(cast<NamedDecl>(D), AdditionalAbiTags);
   }
 
   if (const NamedDecl *ND = dyn_cast<NamedDecl>(RD ? RD : D)) {
     unsigned disc;
     if (Context.getNextDiscriminator(ND, disc)) {
       if (disc < 10)
         Out << '_' << disc;
       else
         Out << "__" << disc << '_';
     }
   }
 }
 
 void CXXNameMangler::mangleBlockForPrefix(const BlockDecl *Block) {
   if (GetLocalClassDecl(Block)) {
-    mangleLocalName(Block);
+    mangleLocalName(Block, /* AdditionalAbiTags */ nullptr);
     return;
   }
   const DeclContext *DC = getEffectiveDeclContext(Block);
   if (isLocalContainerContext(DC)) {
-    mangleLocalName(Block);
+    mangleLocalName(Block, /* AdditionalAbiTags */ nullptr);
     return;
   }
   manglePrefix(getEffectiveDeclContext(Block));
   mangleUnqualifiedBlock(Block);
 }
 
 void CXXNameMangler::mangleUnqualifiedBlock(const BlockDecl *Block) {
   if (Decl *Context = Block->getBlockManglingContextDecl()) {
     if ((isa<VarDecl>(Context) || isa<FieldDecl>(Context)) &&
         Context->getDeclContext()->isRecord()) {
-      if (const IdentifierInfo *Name
-            = cast<NamedDecl>(Context)->getIdentifier()) {
-        mangleSourceName(Name);
-        Out << 'M';            
+      const auto *ND = cast<NamedDecl>(Context);
+      if (ND->getIdentifier()) {
+        mangleSourceNameWithAbiTags(ND);
+        Out << 'M';
       }
     }
   }
 
   // If we have a block mangling number, use it.
   unsigned Number = Block->getBlockManglingNumber();
   // Otherwise, just make up a number. It doesn't matter what it is because
   // the symbol in question isn't externally visible.
void CXXNameMangler::mangleLambda(const CXXRecordDecl *Lambda) {
   // since a closure type will always be mangled with a prefix, it's easier
   // to emit that last part of the prefix here.
   if (Decl *Context = Lambda->getLambdaContextDecl()) {
     if ((isa<VarDecl>(Context) || isa<FieldDecl>(Context)) &&
         Context->getDeclContext()->isRecord()) {
       if (const IdentifierInfo *Name
             = cast<NamedDecl>(Context)->getIdentifier()) {
         mangleSourceName(Name);
-        Out << 'M';            
+        Out << 'M';
       }
     }
   }
 
   Out << "Ul";
   const FunctionProtoType *Proto = Lambda->getLambdaTypeInfo()->getType()->
                                    getAs<FunctionProtoType>();
   mangleBareFunctionType(Proto, /*MangleReturnType=*/false,
void CXXNameMangler::manglePrefix(const DeclContext *DC, bool NoFunction) {
   
   // Check if we have a template.
   const TemplateArgumentList *TemplateArgs = nullptr;
   if (const TemplateDecl *TD = isTemplate(ND, TemplateArgs)) {
     mangleTemplatePrefix(TD);
     mangleTemplateArgs(*TemplateArgs);
   } else {
     manglePrefix(getEffectiveDeclContext(ND), NoFunction);
-    mangleUnqualifiedName(ND);
+    mangleUnqualifiedName(ND, nullptr);
   }
 
   addSubstitution(ND);
 }
 
 void CXXNameMangler::mangleTemplatePrefix(TemplateName Template) {
   // <template-prefix> ::= <prefix> <template unqualified-name>
   //                   ::= <template-param>
   //                   ::= <substitution>
   if (TemplateDecl *TD = Template.getAsTemplateDecl())
     return mangleTemplatePrefix(TD);
 
   if (QualifiedTemplateName *Qualified = Template.getAsQualifiedTemplateName())
     manglePrefix(Qualified->getQualifier());
-  
   if (OverloadedTemplateStorage *Overloaded
                                       = Template.getAsOverloadedTemplate()) {
     mangleUnqualifiedName(nullptr, (*Overloaded->begin())->getDeclName(),
-                          UnknownArity);
+                          UnknownArity, nullptr);
     return;
   }
-   
   DependentTemplateName *Dependent = Template.getAsDependentTemplateName();
   assert(Dependent && "Unknown template name kind?");
   if (NestedNameSpecifier *Qualifier = Dependent->getQualifier())
     manglePrefix(Qualifier);
-  mangleUnscopedTemplateName(Template);
+  mangleUnscopedTemplateName(Template, /* AdditionalAbiTags */ nullptr);
 }
 
 void CXXNameMangler::mangleTemplatePrefix(const TemplateDecl *ND,
                                           bool NoFunction) {
   // <template-prefix> ::= <prefix> <template unqualified-name>
   //                   ::= <template-param>
   //                   ::= <substitution>
   // <template-template-param> ::= <template-param>
   //                               <substitution>
 
   if (mangleSubstitution(ND))
     return;
 
   // <template-template-param> ::= <template-param>
   if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(ND)) {
     mangleTemplateParameter(TTP->getIndex());
   } else {
     manglePrefix(getEffectiveDeclContext(ND), NoFunction);
-    mangleUnqualifiedName(ND->getTemplatedDecl());
+    mangleUnqualifiedName(ND->getTemplatedDecl(), nullptr);
   }
 
   addSubstitution(ND);
 }
 
 /// Mangles a template name under the production <type>.  Required for
 /// template template arguments.
 ///   <type> ::= <class-enum-type>
unresolvedType:
     // sanctioned for a substituted template parameter, though.
     mangleType(Ty);
 
     // We never want to print 'E' directly after an unresolved-type,
     // so we return directly.
     return true;
 
   case Type::Typedef:
-    mangleSourceName(cast<TypedefType>(Ty)->getDecl()->getIdentifier());
+    mangleSourceNameWithAbiTags(cast<TypedefType>(Ty)->getDecl());
     break;
 
   case Type::UnresolvedUsing:
-    mangleSourceName(
-        cast<UnresolvedUsingType>(Ty)->getDecl()->getIdentifier());
+    mangleSourceNameWithAbiTags(
+        cast<UnresolvedUsingType>(Ty)->getDecl());
     break;
 
   case Type::Enum:
   case Type::Record:
-    mangleSourceName(cast<TagType>(Ty)->getDecl()->getIdentifier());
+    mangleSourceNameWithAbiTags(cast<TagType>(Ty)->getDecl());
     break;
 
   case Type::TemplateSpecialization: {
     const TemplateSpecializationType *TST =
         cast<TemplateSpecializationType>(Ty);
     TemplateName TN = TST->getTemplateName();
     switch (TN.getKind()) {
     case TemplateName::Template:
     case TemplateName::QualifiedTemplate: {
       TemplateDecl *TD = TN.getAsTemplateDecl();
 
       // If the base is a template template parameter, this is an
       // unresolved type.
       assert(TD && "no template for template specialization type");
       if (isa<TemplateTemplateParmDecl>(TD))
         goto unresolvedType;
 
-      mangleSourceName(TD->getIdentifier());
+      mangleSourceNameWithAbiTags(TD);
       break;
     }
 
     case TemplateName::OverloadedTemplate:
     case TemplateName::DependentTemplate:
       llvm_unreachable("invalid base for a template specialization type");
 
     case TemplateName::SubstTemplateTemplateParm: {
case Type::TemplateSpecialization: {
     }
     }
 
     mangleTemplateArgs(TST->getArgs(), TST->getNumArgs());
     break;
   }
 
   case Type::InjectedClassName:
-    mangleSourceName(
-        cast<InjectedClassNameType>(Ty)->getDecl()->getIdentifier());
+    mangleSourceNameWithAbiTags(
+        cast<InjectedClassNameType>(Ty)->getDecl());
     break;
 
   case Type::DependentName:
     mangleSourceName(cast<DependentNameType>(Ty)->getIdentifier());
     break;
 
   case Type::DependentTemplateSpecialization: {
     const DependentTemplateSpecializationType *DTST =
case DeclarationName::CXXLiteralOperatorName:
     return;
 
   case DeclarationName::CXXOperatorName:
     mangleOperatorName(Name.getCXXOverloadedOperator(), Arity);
     break;
   }
 }
 
-
-
 void
 CXXNameMangler::mangleOperatorName(OverloadedOperatorKind OO, unsigned Arity) {
   switch (OO) {
   // <operator-name> ::= nw     # new
   case OO_New: Out << "nw"; break;
   //              ::= na        # new[]
   case OO_Array_New: Out << "na"; break;
   //              ::= dl        # delete
case BuiltinType::NullPtr:
     Out << "Dn";
     break;
 
 #define BUILTIN_TYPE(Id, SingletonId)
 #define PLACEHOLDER_TYPE(Id, SingletonId) \
   case BuiltinType::Id:
 #include "clang/AST/BuiltinTypes.def"
   case BuiltinType::Dependent:
+    if (!NullOut)
       llvm_unreachable("mangling a placeholder type");
+    break;
   case BuiltinType::ObjCId:
     Out << "11objc_object";
     break;
   case BuiltinType::ObjCClass:
     Out << "10objc_class";
     break;
   case BuiltinType::ObjCSel:
     Out << "13objc_selector";
void CXXNameMangler::mangleType(const InjectedClassNameType *T) {
   // Mangle injected class name types as if the user had written the
   // specialization out fully.  It may not actually be possible to see
   // this mangling, though.
   mangleType(T->getInjectedSpecializationType());
 }
 
 void CXXNameMangler::mangleType(const TemplateSpecializationType *T) {
   if (TemplateDecl *TD = T->getTemplateName().getAsTemplateDecl()) {
-    mangleName(TD, T->getArgs(), T->getNumArgs());
+    mangleTemplateName(TD, T->getArgs(), T->getNumArgs());
   } else {
     if (mangleSubstitution(QualType(T, 0)))
       return;
     
     mangleTemplatePrefix(T->getTemplateName());
     
     // FIXME: GCC does not appear to mangle the template arguments when
     // the template in question is a dependent template name. Should we
#include "clang/AST/StmtNodes.inc"
   case Expr::ArrayTypeTraitExprClass:
   case Expr::ExpressionTraitExprClass:
   case Expr::VAArgExprClass:
   case Expr::CUDAKernelCallExprClass:
   case Expr::AsTypeExprClass:
   case Expr::PseudoObjectExprClass:
   case Expr::AtomicExprClass:
   {
+    if (!NullOut) {
       // As bad as this diagnostic is, it's better than crashing.
       DiagnosticsEngine &Diags = Context.getDiags();
       unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                        "cannot yet mangle expression type %0");
       Diags.Report(E->getExprLoc(), DiagID)
         << E->getStmtClassName() << E->getSourceRange();
+    }
     break;
   }
 
   case Expr::CXXUuidofExprClass: {
     const CXXUuidofExpr *UE = cast<CXXUuidofExpr>(E);
     if (UE->isTypeOperand()) {
       QualType UuidT = UE->getTypeOperand(Context.getASTContext());
       Out << "u8__uuidoft";
void CXXNameMangler::addSubstitution(TemplateName Template) {
   addSubstitution(reinterpret_cast<uintptr_t>(Template.getAsVoidPointer()));
 }
 
 void CXXNameMangler::addSubstitution(uintptr_t Ptr) {
   assert(!Substitutions.count(Ptr) && "Substitution already exists!");
   Substitutions[Ptr] = SeqID++;
 }
 
+CXXNameMangler::AbiTagSet
+CXXNameMangler::makeFunctionReturnTypeTags(const FunctionDecl *FD) {
+  // When derived abi tags are disabled there is no need to make any list.
+  if (DisableDerivedAbiTags)
+    return AbiTagSet();
+
+  llvm::raw_null_ostream NullOutStream;
+  CXXNameMangler TrackReturnTypeTags(*this, NullOutStream);
+  TrackReturnTypeTags.disableDerivedAbiTags();
+
+  const FunctionProtoType *Proto =
+      cast<FunctionProtoType>(FD->getType()->getAs<FunctionType>());
+  TrackReturnTypeTags.FunctionTypeDepth.enterResultType();
+  TrackReturnTypeTags.mangleType(Proto->getReturnType());
+  TrackReturnTypeTags.FunctionTypeDepth.leaveResultType();
+
+  return TrackReturnTypeTags.AbiTagsRoot.getUsedAbiTags();
+}
+
+CXXNameMangler::AbiTagSet
+CXXNameMangler::makeVariableTypeTags(const VarDecl *VD) {
+  // When derived abi tags are disabled there is no need to make any list.
+  if (DisableDerivedAbiTags)
+    return AbiTagSet();
+
+  llvm::raw_null_ostream NullOutStream;
+  CXXNameMangler TrackVariableType(*this, NullOutStream);
+  TrackVariableType.disableDerivedAbiTags();
+
+  TrackVariableType.mangleType(VD->getType());
+
+  return TrackVariableType.AbiTagsRoot.getUsedAbiTags();
+}
+
+bool CXXNameMangler::shouldHaveAbiTags(ItaniumMangleContextImpl &C,
+                                       const VarDecl *VD) {
+  llvm::raw_null_ostream NullOutStream;
+  CXXNameMangler TrackAbiTags(C, NullOutStream, nullptr, true);
+  TrackAbiTags.mangle(VD);
+  return TrackAbiTags.AbiTagsRoot.getUsedAbiTags().size();
+}
+
 //
 
 /// Mangles the name of the declaration D and emits that name to the given
 /// output stream.
 ///
 /// If the declaration D requires a mangled name, this routine will emit that
 /// mangled name to \p os and return true. Otherwise, \p os will be unchanged
 /// and this routine will return false. In this case, the caller should just

 }
 
 /// Returns the mangled name for a guard variable for the passed in VarDecl.
 void ItaniumMangleContextImpl::mangleStaticGuardVariable(const VarDecl *D,
                                                          raw_ostream &Out) {
   //  <special-name> ::= GV <object name>       # Guard variable for one-time
   //                                            # initialization
   CXXNameMangler Mangler(*this, Out);
+  // GCC 5.3.0 doesn't emit derived ABI tags for local names but that seems to
+  // be a bug that is fixed in trunk.
   Mangler.getStream() << "_ZGV";
   Mangler.mangleName(D);
 }
 
 void ItaniumMangleContextImpl::mangleDynamicInitializer(const VarDecl *MD,
                                                         raw_ostream &Out) {
   // These symbols are internal in the Itanium ABI, so the names don't matter.
   // Clang has traditionally used this symbol and allowed LLVM to adjust it to

lib/Sema/SemaDeclAttr.cpp

static void handleAbiTagAttr(Sema &S, Decl *D, const AttributeList &Attr) {
 
   // Store tags sorted and without duplicates.
   std::sort(Tags.begin(), Tags.end());
   Tags.erase(std::unique(Tags.begin(), Tags.end()), Tags.end());
 
   D->addAttr(::new (S.Context)
              AbiTagAttr(Attr.getRange(), S.Context, Tags.data(), Tags.size(),
                         Attr.getAttributeSpellingListIndex()));
-
-  // FIXME: remove this warning as soon as mangled part is ready.
-  S.Diag(Attr.getRange().getBegin(), diag::warn_attribute_ignored)
-        << Attr.getName();
 }
 
 static void handleARMInterruptAttr(Sema &S, Decl *D,
                                    const AttributeList &Attr) {
   // Check the attribute arguments.
   if (Attr.getNumArgs() > 1) {
     S.Diag(Attr.getLoc(), diag::err_attribute_too_many_arguments)
       << Attr.getName() << 1;

test/CodeGenCXX/mangle-abi-tag.cpp

+// RUN: %clang_cc1 %s -emit-llvm -triple %itanium_abi_triple -std=c++11 -o - | FileCheck %s
+// RUN: %clang_cc1 %s -emit-llvm -triple i686-linux-gnu -std=c++11 -o - | FileCheck %s
+// RUN: %clang_cc1 %s -emit-llvm -triple x86_64-linux-gnu -std=c++11 -o - | FileCheck %s
+
+struct __attribute__((abi_tag("A", "B"))) A { };
+
+struct B: A { };
+
+template<class T>
+
+struct C {
+};
+
+struct D { A* p; };
+
+template<class T>
+struct __attribute__((abi_tag("C", "D"))) E {
+};
+
+struct __attribute__((abi_tag("A", "B"))) F { };
+
+A a1;
+// CHECK-DAG: @_Z2a1B1AB1B =
+
+__attribute__((abi_tag("C", "D")))
+A a2;
+// CHECK-DAG: @_Z2a2B1AB1BB1CB1D =
+
+B a3;
+// CHECK-DAG: @a3 =
+
+C<A> a4;
+// CHECK-DAG: @_Z2a4B1AB1B =
+
+D a5;
+// CHECK-DAG: @a5 =
+
+E<int> a6;
+// CHECK-DAG: @_Z2a6B1CB1D =
+
+E<A> a7;
+// CHECK-DAG: @_Z2a7B1AB1BB1CB1D =
+
+template<>
+struct E<float> {
+  static float a8;
+};
+float E<float>::a8;
+// CHECK-DAG: @_ZN1EB1CB1DIfE2a8E =
+
+template<>
+struct E<F> {
+  static bool a9;
+};
+bool E<F>::a9;
+// CHECK-DAG: @_ZN1EB1CB1DI1FB1AB1BE2a9E =
+
+struct __attribute__((abi_tag("A", "B"))) A10 {
+  virtual ~A10() {}
+} a10;
+// vtable
+// CHECK-DAG: @_ZTV3A10B1AB1B =
+// typeinfo
+// CHECK-DAG: @_ZTI3A10B1AB1B =
+
+struct __attribute__((abi_tag("A"))) B11 {
+  static A10 b;
+};
+A10 B11::b;
+// B11[abi:A]::b[abi:B]
+// CHECK-DAG: @_ZN3B11B1A1bB1BE =
+
+__attribute__ ((abi_tag("C", "D")))
+void* f1() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f1B1CB1Dv(
+
+__attribute__ ((abi_tag("C", "D")))
+A* f2() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f2B1AB1BB1CB1Dv(
+
+B* f3() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f3v(
+
+C<A>* f4() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f4B1AB1Bv(
+
+D* f5() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f5v(
+
+E<char>* f6() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f6B1CB1Dv(
+
+E<A>* f7() {
+  return 0;
+}
+// CHECK-DAG: define {{.*}} @_Z2f7B1AB1BB1CB1Dv(
+
+void f8(E<A>*) {
+}
+// CHECK-DAG: define {{.*}} @_Z2f8P1EB1CB1DI1AB1AB1BE(
+
+inline namespace Names1 __attribute__((__abi_tag__)) {
+    class C1 {};
+}
+C1 f9() { return C1(); }
+// CHECK-DAG: @_Z2f9B6Names1v(
+
+inline namespace Names2 __attribute__((__abi_tag__("Tag1", "Tag2"))) {
+    class C2 {};
+}
+C2 f10() { return C2(); }
+// CHECK-DAG: @_Z3f10B4Tag1B4Tag2v(
+
+void __attribute__((abi_tag("A"))) f11(A) {}
+// f11[abi:A](A[abi:A][abi:B])
+// CHECK-DAG: define {{.*}} @_Z3f11B1A1AB1AB1B(
+
+A f12(A) { return A(); }
+// f12(A[abi:A][abi:B])
+// CHECK-DAG: define {{.*}} @_Z3f121AB1AB1B(
+
+inline void f13() {
+  struct L {
+    static E<int>* foo() {
+      static A10 a;
+      return 0;
+    }
+  };
+  L::foo();
+}
+void f13_test() {
+  f13();
+}
+// f13()::L::foo[abi:C][abi:D]()
+// CHECK-DAG: define linkonce_odr %struct.E* @_ZZ3f13vEN1L3fooB1CB1DEv(
+
+// f13()::L::foo[abi:C][abi:D]()::a[abi:A][abi:B]
+// CHECK-DAG: @_ZZZ3f13vEN1L3fooB1CB1DEvE1aB1AB1B =
+
+// guard variable for f13()::L::foo[abi:C][abi:D]()::a[abi:A][abi:B]
+// CHECK-DAG: @_ZGVZZ3f13vEN1L3fooB1CB1DEvE1aB1AB1B =
+
+struct __attribute__((abi_tag("TAG"))) A14 {
+  A14 f14();
+};
+A14 A14::f14() {
+  return A14();
+}
+// A14[abi:TAG]::f14()
+// CHECK-DAG: define void @_ZN3A14B3TAG3f14Ev(
+
+template<class T>
+T f15() {
+  return T();
+}
+void f15_test() {
+  f15<A14>();
+}
+// A14[abi:TAG] f15<A14[abi:TAG]>()
+// CHECK-DAG: define linkonce_odr void @_Z3f15I3A14B3TAGET_v(
+
+template<class T>
+A14 f16() {
+  return A14();
+}
+void f16_test() {
+  f16<int>();
+}
+// A14[abi:TAG] f16<int>()
+// CHECK-DAG: define linkonce_odr void @_Z3f16IiE3A14B3TAGv(

test/PCH/attrs.c

 // Test this without pch.
 // RUN: %clang_cc1 -include %s -fsyntax-only -verify %s
 
 // Test with pch.
 // RUN: %clang_cc1 -emit-pch -o %t %s
 // RUN: %clang_cc1 -include-pch %t -fsyntax-only -verify %s 
 
 #ifndef HEADER
 #define HEADER
 
 int f(int) __attribute__((visibility("default"), overloadable));
-int g(int) __attribute__((abi_tag("foo", "bar", "baz"), no_sanitize("address", "memory"))); // expected-warning {{ignored}}
+int g(int) __attribute__((abi_tag("foo", "bar", "baz"), no_sanitize("address", "memory")));
 
 #else
 
 double f(double); // expected-error{{overloadable}}
                   // expected-note@11{{previous overload}}
 void h() { g(0); }
 
 #endif

test/SemaCXX/attr-abi-tag-syntax.cpp

 } // namespace N1
 
 namespace N2 {
 
 inline namespace __attribute__((__abi_tag__)) {}
 // expected-warning@-1 {{'abi_tag' attribute on anonymous namespace ignored}}
 
 inline namespace N __attribute__((__abi_tag__)) {}
-// FIXME: remove this warning as soon as attribute fully supported.
-// expected-warning@-2 {{'__abi_tag__' attribute ignored}}
 
 } // namespcace N2
 
 __attribute__((abi_tag("B", "A"))) extern int a1;
-// FIXME: remove this warning as soon as attribute fully supported.
-// expected-warning@-2 {{'abi_tag' attribute ignored}}
 
 __attribute__((abi_tag("A", "B"))) extern int a1;
 // expected-note@-1 {{previous declaration is here}}
-// FIXME: remove this warning as soon as attribute fully supported.
-// expected-warning@-3 {{'abi_tag' attribute ignored}}
 
 __attribute__((abi_tag("A", "C"))) extern int a1;
 // expected-error@-1 {{'abi_tag' C missing in original declaration}}
-// FIXME: remove this warning as soon as attribute fully supported.
-// expected-warning@-3 {{'abi_tag' attribute ignored}}
 
 extern int a2;
 // expected-note@-1 {{previous declaration is here}}
 __attribute__((abi_tag("A")))extern int a2;
 // expected-error@-1 {{cannot add 'abi_tag' attribute in a redeclaration}}
-// FIXME: remove this warning as soon as attribute fully supported.
-// expected-warning@-3 {{'abi_tag' attribute ignored}}