[PATCH, PR45098, 3/10]
Tom de Vries
vries@codesourcery.com
Wed May 18 13:00:00 GMT 2011
Hi Zdenek,
thanks for the review.
On 05/18/2011 09:26 AM, Zdenek Dvorak wrote:
>> 2011-05-05 Tom de Vries <tom@codesourcery.com>
>>
>> PR target/45098
>> * tree-ssa-loop-ivopts.c (computation_cost): Prevent cost of 0.
>
> this looks strange. Something like
>
> cost = seq_cost (seq, speed);
> if (MEM_P (rslt))
> the current code;
> else
> cost += rtx_cost (rslt, SET, speed));
>
> would make more sense to me (if I understand correctly what you are
> trying to achieve).
>
Sorry for not putting an explanation in the first place.
I'm trying to achieve that the cost of forcing an int into a reg is not
0. Currently, if the expansion results in an rtx expression rather than
an insn, seq is NULL and seq_cost returns 0, after which
computation_cost returns 0:
...
(gdb) call debug_generic_expr (expr)
2000
(gdb) call debug_rtx (rslt)
(const_int 2000 [0x7d0])
(gdb) p seq
$5 = (rtx) 0x0
...
Using an assert on an x86_64 build, I found this case where seq != NULL_RTX:
...
gdb) call debug_generic_expr (expr)
(int) ((unsigned int) ivtmp.11 * 8)
(gdb) call debug_rtx (rslt)
(reg:SI 62)
(gdb) call debug_rtx (seq)
(insn 4 0 0 (parallel [
(set (reg:SI 62)
(ashift:SI (subreg:SI (reg:DI 59 [ ivtmp.11 ]) 0)
(const_int 3 [0x3])))
(clobber (reg:CC 17 flags))
]) -1
(nil))
...
we don't need to additionally count a regcopy of r62 on top of seq_cost
in this case.
How about:
...
@@ -2866,6 +2878,8 @@ computation_cost (tree expr, bool speed)
if (MEM_P (rslt))
cost += address_cost (XEXP (rslt, 0), TYPE_MODE (type),
TYPE_ADDR_SPACE (type), speed);
+ else if (!REG_P (rslt))
+ cost += (unsigned)rtx_cost (rslt, SET, speed);
return cost;
}
...
?
Thanks
- Tom
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