[GHC] #9504: LLVM backend TBAA is too aggressive

[GHC]

#9504: LLVM backend TBAA is too aggressive
-------------------------------------+-------------------------------------
        Reporter:  rwbarton          |                Owner:
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (LLVM)   |              Version:  7.8.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:  9308
 Related Tickets:                    |  Differential Rev(s):  Phab:D2758
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"90fae01c326bf8b0802b4e8968f84886be4e1380/ghc"
 90fae01c/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="90fae01c326bf8b0802b4e8968f84886be4e1380"
 Fix LLVM TBAA metadata

 Accesses through a Cmm local are currently reported as having the
 "other" type, which can only alias other "other" accesses.  However,
 this assumption is incorrect, which can result in silent bad LLVM
 codegen.

 Fixes #9308.
 Fixes #9504.

 Test Plan: GHC CI

 Reviewers: rwbarton, austin, bgamari

 Reviewed By: bgamari

 Subscribers: michalt, thomie

 Differential Revision: https://phabricator.haskell.org/D2758

 GHC Trac Issues: #9125, #9308, #9504
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9504#comment:9>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler