[llvm] r228180 - Utils: Resolve cycles under distinct MDNodes

[Duncan P. N. Exon Smith]

> On 2015-Feb-04, at 13:00, Hans Wennborg <hans at chromium.org> wrote:
> 
> On Wed, Feb 4, 2015 at 11:44 AM, Duncan P. N. Exon Smith
> <dexonsmith at apple.com> wrote:
>> Author: dexonsmith
>> Date: Wed Feb  4 13:44:34 2015
>> New Revision: 228180
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=228180&view=rev
>> Log:
>> Utils: Resolve cycles under distinct MDNodes
>> 
>> Track unresolved nodes under distinct `MDNode`s during `MapMetadata()`,
>> and resolve them at the end.  Previously, these cycles wouldn't get
>> resolved.
> 
> PR22456 reproduces on the 3.6 branch. Should we merge this fix?

Yes we should, but it doesn't merge cleanly since `MapMetadata()` has
been essentially rewritten since then.

I'm just compiling a fix now.  I'll let you know when I'm done.