[Bug middle-end/58564] [4.7/4.8/4.9 Regression] possible wrong code bug at -O0

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58564

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 30932
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30932&action=edit
gcc49-pr58564.patch

Untested fix.

Note, this patch doesn't attempt to fold the zero extension of something < 0
into 0 resp. side-effects of something, 0, because I think we are generally
trying to move away from adding further new stuff to fold-const.c, and rather
should improve GIMPLE optimizations.