* mov arguments are still the same
@ 2011-03-16 18:19 Paulo J. Matos
2011-03-24 17:21 ` Paulo J. Matos
0 siblings, 1 reply; 2+ messages in thread
From: Paulo J. Matos @ 2011-03-16 18:19 UTC (permalink / raw)
To: gcc
Hi,
I have touched this subject before:
http://thread.gmane.org/gmane.comp.gcc.devel/116198/focus=116200
Now, at the time I didn't pursue this issue but now with 4.4.4 this
keeps happening and I traced it to the cprop_hardreg replacing a
register which makes the set insn having the same source and dest.
Here's insn 32 from pass 183:ce3
(insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL)
(reg/f:QI 8 @H'fff9 [33])) 4 {*movqi} (expr_list:REG_DEAD
(reg/f:QI 8 @H'fff9 [33])
(expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y)
(const_int 1 [0x1]))
(nil))))
Now the same insn after the following pass 185:cprop_hardreg
insn 32: replaced reg 8 with 1
...
(insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL)
(reg/f:QI 1 AL [33])) 4 {*movqi} (expr_list:REG_DEAD (reg/f:QI
8 @H'fff9 [33])
(expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y)
(const_int 1 [0x1]))
(nil))))
This stays as is until assembler generation, which is really annoying
cause it generates an instruction (which is basically a nop) like:
...
mov AL,AL
...
Is this a known issue? I can't see how this is a problem with my backend
but might as well be. Maybe cprop_regmove should check if it is making
the src equal to dest and if it is remove the insn?
Any suggestions?
--
PMatos
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: mov arguments are still the same
2011-03-16 18:19 mov arguments are still the same Paulo J. Matos
@ 2011-03-24 17:21 ` Paulo J. Matos
0 siblings, 0 replies; 2+ messages in thread
From: Paulo J. Matos @ 2011-03-24 17:21 UTC (permalink / raw)
To: gcc
Let me revive this thread and ask for suggestions/tips on the issue below.
Cheers,
PMatos
On 16/03/11 18:19, Paulo J. Matos wrote:
> Hi,
>
> I have touched this subject before:
> http://thread.gmane.org/gmane.comp.gcc.devel/116198/focus=116200
>
> Now, at the time I didn't pursue this issue but now with 4.4.4 this
> keeps happening and I traced it to the cprop_hardreg replacing a
> register which makes the set insn having the same source and dest.
>
> Here's insn 32 from pass 183:ce3
>
> (insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL)
> (reg/f:QI 8 @H'fff9 [33])) 4 {*movqi} (expr_list:REG_DEAD (reg/f:QI 8
> @H'fff9 [33])
> (expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y)
> (const_int 1 [0x1]))
> (nil))))
>
>
> Now the same insn after the following pass 185:cprop_hardreg
>
>
> insn 32: replaced reg 8 with 1
>
> ...
>
> (insn 32 31 33 4 h.c:51 (set (reg:QI 1 AL)
> (reg/f:QI 1 AL [33])) 4 {*movqi} (expr_list:REG_DEAD (reg/f:QI 8 @H'fff9
> [33])
> (expr_list:REG_EQUAL (plus:QI (reg/f:QI 6 Y)
> (const_int 1 [0x1]))
> (nil))))
>
>
> This stays as is until assembler generation, which is really annoying
> cause it generates an instruction (which is basically a nop) like:
> ...
> mov AL,AL
> ...
>
> Is this a known issue? I can't see how this is a problem with my backend
> but might as well be. Maybe cprop_regmove should check if it is making
> the src equal to dest and if it is remove the insn?
>
> Any suggestions?
>
> --
> PMatos
>
>
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