[Bug middle-end/55152] New: MAX_EXPR(a,-a) is really ABS_EXPR(a)

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55152

             Bug #: 55152
           Summary: MAX_EXPR(a,-a) is really ABS_EXPR(a)
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: glisse@gcc.gnu.org


I tried compiling this code with -Ofast, but *.optimized still only contained a
MAX_EXPR and not an ABS_EXPR (the back-end didn't find the optimization
either).

double f(double a){
  return (a>=-a)?a:-a;
}

It seems that some simple code in fold-const.c could help (fold is called from
the front-end for COND_EXPR), not sure if anything would call it if -a went
though a temporary variable though.