On Tue, Oct 16, 2012 at 12:15 PM, Steven Bosscher wrote:
> On Mon, Oct 15, 2012 at 3:26 PM, Steven Bosscher wrote:
>> On Mon, Oct 15, 2012 at 3:21 PM, Paolo Bonzini wrote:
>>> Il 15/10/2012 14:53, Steven Bosscher ha scritto:
>>>> I think I've shown above that we're all looking at the wrong pass...
>>>
>>> I think you have... so we want a patch like this?
>>
>> I don't think so. df_kill_notes is already supposed to take care of this.
>
> But it doesn't because if the SET_DEST of an insn is the same as the
> register dieing in the insn's REG_EQUAL note, the reg is live at the
> end of the insn and so the note stays:
>
> Breakpoint 2, df_kill_notes (insn=0x7ffff5e3e7e0, live=0x7fffffffda90)
> at ../../trunk/gcc/df-problems.c:2833
> 2833 rtx *pprev = ®_NOTES (insn);
> 1: debug_rtx(insn) = (insn 79 50 52 8 (set (reg:DI 72 [ ivtmp.17D.1758 ])
> (reg:DI 103 [ ivtmp.17D.1758 ])) -1
> (expr_list:REG_DEAD (reg:DI 103 [ ivtmp.17D.1758 ])
> (expr_list:REG_EQUAL (plus:DI (reg:DI 72 [ ivtmp.17D.1758 ])
> (const_int 24 [0x18]))
> (nil))))
> void
> (gdb) undisp 1
> (gdb) p debug_bitmap(live)
>
> first = 0x1627200 current = 0x1627200 indx = 0
> 0x1627200 next = (nil) prev = (nil) indx = 0
> bits = { 6 7 16 20 72 82 85 87 }
> $2 = void
> (gdb)
>
>
> So GCC should be looking at whether the reg in the REG_EQUAL note is
> dead *before* the insn.
>
> Bottom line: This is a bug in df_kill_notes.I think this should fix it. Can't test it right now, so help appreciated (Honza: hint hint! ;-) Ciao! Steven
remove_dead_eq_notes.diff
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