https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83459
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amonakov at gcc dot gnu.org,
| |jakub at gcc dot gnu.org,
| |vmakarov at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
So, in this case we have:
(gdb) p debug_rtx (first[0])
(insn 4 2 3 2 (set (reg/v:SI 95 [ e ])
(reg:SI 4 si [ e ])) "pr83459.c":6 86 {*movsi_internal}
(expr_list:REG_DEAD (reg:SI 4 si [ e ])
(nil)))
$21 = void
(gdb) p debug_rtx (first[1])
(insn 15 14 16 4 (set (reg:SI 98 [ b ])
(sign_extend:SI (mem/c:HI (symbol_ref:DI ("b") [flags 0x2] <var_decl
0x7ffff7ff5ea0 b>) [1 b+0 S2 A16]))) "pr83459.c":8 153 {extendhisi2}
(nil))
$22 = void
(gdb) p debug_rtx (first[2])
(insn 9 3 10 2 (set (reg:SI 96 [ a ])
(sign_extend:SI (mem/c:HI (symbol_ref:DI ("a") [flags 0x2] <var_decl
0x7ffff7ff5e10 a>) [1 a+0 S2 A16]))) "pr83459.c":7 153 {extendhisi2}
(nil))
and
p rank_for_schedule (&first[0], &first[1])
$24 = -1
determined by
val = (dep_list_size (tmp2, SD_LIST_FORW)
- dep_list_size (tmp, SD_LIST_FORW));
if (flag_sched_dep_count_heuristic && val != 0)
return rfs_result (RFS_DEP_COUNT, val, tmp, tmp2);
where val is -1, then
p rank_for_schedule (&first[1], &first[2])
$25 = -4
determined by:
/* If insns are equally good, sort by INSN_LUID (original insn order),
so that we make the sort stable. This minimizes instruction movement,
thus minimizing sched's effect on debugging and cross-jumping. */
return rfs_result (RFS_TIE, INSN_LUID (tmp) - INSN_LUID (tmp2), tmp, tmp2);
and finally:
p rank_for_schedule (&first[0], &first[2])
$26 = 1
determined by:
/* Prefer instructions that occur earlier in the model schedule. */
if (sched_pressure == SCHED_PRESSURE_MODEL
&& INSN_BB (tmp) == target_bb && INSN_BB (tmp2) == target_bb)
{
diff = model_index (tmp) - model_index (tmp2);
gcc_assert (diff != 0);
return rfs_result (RFS_PRESSURE_INDEX, diff, tmp, tmp2);
}
which is checked earliest. If we want a stable sort, I'm afraid for
SCHED_PRESSURE_MODEL we need to sort insns where INSN_BB (tmp) == target_bb and
INSN_BB (tmp2) != target_bb or INSN_BB (tmp2) == target_bb and INSN_BB (tmp) !=
target_bb regardless of dep_list_size.
Thoughts on this?
