Michael Matz writes:
> On Wed, 6 Jul 2011, Richard Sandiford wrote:
>> But there's still the separate point that, when not considering
>> addresses, this transformation doesn't seem to be a win, except
>> in the constant case.
>
> My first example shows that on some targets it can be a win, also i
Hi,
On Wed, 6 Jul 2011, Richard Sandiford wrote:
> > It's only a strict win on targets where the addition in "(q-p) + n"
> > can be hidden in either address generation, or combined with other
> > arithmetic, or on all targets if (q-p) is a constant.
>
> Agreed on the constant thing. But is it
Michael Matz writes:
> On Wed, 6 Jul 2011, Richard Sandiford wrote:
>> But what I mean is: even with your starting loop, I'm comparing the
>> transformation that this code does with the alternative, but rejected,
>> transformation of simply treating both addresses as separate ivs. I.e.:
>>
>>
Hi,
On Wed, 6 Jul 2011, Richard Sandiford wrote:
> But what I mean is: even with your starting loop, I'm comparing the
> transformation that this code does with the alternative, but rejected,
> transformation of simply treating both addresses as separate ivs. I.e.:
>
> i=0; i < end; i+=1
>
Michael Matz writes:
> On Wed, 6 Jul 2011, Richard Sandiford wrote:
>> > If the target allows (q-p)[n] to be used directly as an address, and
>> > if the target has no post-increment instruction, then it might be
>> > better. But I think it's a loss on other targets. It might even be a
>> > lo
Hi,
On Wed, 6 Jul 2011, Richard Sandiford wrote:
> > If the target allows (q-p)[n] to be used directly as an address, and
> > if the target has no post-increment instruction, then it might be
> > better. But I think it's a loss on other targets. It might even be a
> > loss on targets (like Po
Richard Sandiford writes:
> Michael Matz writes:
>> On Wed, 6 Jul 2011, Richard Sandiford wrote:
>>> If so, then:
>>>
>>> (a) That doesn't happen at the tree level. The subtraction is still inside
>>> the loop at RTL generation time.
>>>
>>> (b) What's the advantage of introducing a new ho
Michael Matz writes:
> On Wed, 6 Jul 2011, Richard Sandiford wrote:
>> The individual difference_cost and add_cost seem reasonable (4 in each
>> case). I don't understand the reasoning behind the division though. Is
>> the idea that this should be hoisted?
>
> Yes, it should be hoisted outside
Hi,
On Wed, 6 Jul 2011, Richard Sandiford wrote:
> The individual difference_cost and add_cost seem reasonable (4 in each
> case). I don't understand the reasoning behind the division though. Is
> the idea that this should be hoisted?
Yes, it should be hoisted outside the loop. The differenc
