From: "Petar Bajic" <petar.bajic@micronasnit.com>
To: "Ian Lance Taylor" <iant@google.com>
Cc: <gcc-help@gcc.gnu.org>
Subject: Re: adding movz to machine description
Date: Tue, 25 Jul 2006 14:10:00 -0000 [thread overview]
Message-ID: <011301c6aff4$463187d0$4900a8c0@niit.micronasnit.com> (raw)
In-Reply-To: <m3odvdiz2i.fsf@localhost.localdomain>
> That means that the combine pass has replaced it with something else
> which is equivalent which the combine pass thought would be cheaper.
> Look at the generated RTL to see what it turned into. If the
> resulting code is less efficient to run, then you need to adjust your
> costs (the TARGET_RTX_COSTS hook).
>
> Ian
Finally, my instruction is generated.
There is off course one problem, when If Then Else is replaced with my
pattern,
(define_expand "movsicc"
[(set (match_operand:SI 0 "register_operand" "=d,d")
(if_then_else:SI
;;(match_operator 1 "comparison_operator" [(match_operand:SI 3
"register_operand" "=d,d") (const_int 0)])
(eq:SI (match_operand:SI 1 "register_operand" "=d,d") (const_int 0))
(match_operand:SI 2 "register_operand" "=d,d")
(match_dup:SI 0)))]
""
"
{
dlx_compare_op0 = force_reg(SImode, dlx_compare_op0);
emit_insn(gen_movsicc_movz(operands[0], , dlx_compare_op0, operands[2], ,
operands[0], ));
DONE;
}")
previous initialization of destination register is lost.
for example,
d = 7;
if (a > b)
d = in1;
return d;
obviously, d should remain 7 if condition is not true.
pattern is replaced with
(insn 50 18 51 0 (set (reg:SI 47)
(const_int 7 [0x7])) 40 {movsi_general} (nil) ////this use
to be d = 7;
(nil))
(insn 51 50 33 0 (set (reg/v:SI 37 [ d ])
(if_then_else:SI (reg:SI 45)
(reg/v:SI 42 [ h ])
(reg/v:SI 37 [ d ]))) 0 {movsicc_movz} (nil) //// now d is
not initialised??
(nil))
and in next step, insn 50 is removed!
How come else branch got hanging like that?
next prev parent reply other threads:[~2006-07-25 14:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-21 9:55 Petar Bajic
2006-07-21 16:30 ` Ian Lance Taylor
2006-07-25 10:09 ` Petar Bajic
2006-07-25 13:39 ` Ian Lance Taylor
2006-07-25 14:10 ` Petar Bajic [this message]
2006-07-25 14:56 ` Ian Lance Taylor
2006-08-11 12:07 ` Petar Bajic
-- strict thread matches above, loose matches on Subject: below --
2006-07-07 13:54 Help required for c to VCG GDL flow chart Sharad Pratap
2006-07-07 14:24 ` adding movz to machine description Petar Bajic
2006-07-07 17:39 ` Ian Lance Taylor
2006-07-12 11:10 ` Petar Bajic
2006-07-13 7:52 ` Ian Lance Taylor
2006-07-18 12:06 ` Petar Bajic
2006-07-18 14:35 ` Ian Lance Taylor
2006-07-25 18:25 ` Rask Ingemann Lambertsen
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