[Bug middle-end/80362] [5/6/7 Regression] gcc miscompiles arithmetic with signed char

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80362

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
             Status|NEW                         |ASSIGNED
      Known to work|                            |3.4.6, 4.1.2
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot 
gnu.org
   Target Milestone|---                         |5.5
            Summary|gcc miscompiles arithmetic  |[5/6/7 Regression] gcc
                   |with signed char            |miscompiles arithmetic with
                   |                            |signed char
      Known to fail|                            |4.3.6

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fails with -O0 -fstrict-overflow already.  Folded to

    signed char var_1 = -128;
  var_0 = var_1 / -3;
  if (var_0 > 0)

either extract_muldiv or fold_negate.  Mine.