[Bug bootstrap/52287] [4.7 regression] ICE in ready_remove_first, at haifa-sched.c:1927

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52287

--- Comment #8 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2012-02-23 
15:23:44 UTC ---
This reproduces only on Solaris 8 because the sort of the ready list isn't
stable in the presence of debug insns, given that rank_for_schedule isn't
anti-symmetrical:

  if (MAY_HAVE_DEBUG_INSNS)
    {
      /* Schedule debug insns as early as possible.  */
      if (DEBUG_INSN_P (tmp) && !DEBUG_INSN_P (tmp2))
    return -1;
      else if (DEBUG_INSN_P (tmp2))
    return 1;
    }

The following patchlet is enough to get rid of the ICE:

Index: haifa-sched.c
===================================================================
--- haifa-sched.c       (revision 184352)
+++ haifa-sched.c       (working copy)
@@ -1647,7 +1647,7 @@ rank_for_schedule (const void *x, const
       /* Schedule debug insns as early as possible.  */
       if (DEBUG_INSN_P (tmp) && !DEBUG_INSN_P (tmp2))
        return -1;
-      else if (DEBUG_INSN_P (tmp2))
+      else if (DEBUG_INSN_P (tmp2) && !DEBUG_INSN_P (tmp))
        return 1;
     }

as it makes the sort stable and equivalent to the non-Solaris 8 case.