[Bug rtl-optimization/25130] [4.1/4.2 Regression] miscompilation in GCSE

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25130

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|FIXED                       |
      Known to fail|                            |

--- Comment #23 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-13 12:47:14 UTC ---
(In reply to comment #21)
> The patch that was committed (especially the cse.c exp_equiv_p part) seems like
> a big hammer, and it does cause missed optimization opportunities.
> 
> Reverting it on gcc-4.1-branch, and instead applying the patch for PR41033,
> also gives a compiler that correctly compiles this testcase.
> 
> PR41033 adds a test for flag_strict_aliasing to nonverlapping_component_refs_p,
> which corrects the return value for canon_true_dependence mentioned in comment
> #9.
> 
> Steven, are you certain that this patch is necessary in light of this?

As PR49390 shows, yes.