[Bug target/96189] Failure to use eflags from cmpxchg on x86

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96189

Uroš Bizjak <ubizjak at gmail dot com> changed:

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2020-07-15
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |ubizjak at gmail dot com

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 48877
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48877&action=edit
Prototype patch

Introduce peephole2 pattern that removes the comparison in certain cases.
Doubleword cmpxchg is not handled, the doubleword comparison sequence is just
too complicated in this late stage of compilation.