On 5 January 2012 23:40, Peter Alexander <peter.alexander...@gmail.com> wrote:
> On 5/01/12 10:17 PM, Iain Buclaw wrote:
>>
>> On 5 January 2012 22:11, Manu<turkey...@gmail.com> wrote:
>>>
>>> So regarding my assumptions about translating the D front end expressions
>>> to
>>>
>>> GCC? Is that all simpler than I imagine?
>>> Do you think GDC generates optimal code comparable to C code?
>>>
>>> What about pure functions, can you make good on optimisations like
>>> caching
>>> results of pure functions, moving them outside loops, etc?
>>>
>>>
>>
>> I think you are confusing the pure with memoization. I could be wrong
>> however... :)
>>
>
> I think Manu is right:
>
> void foo(int x)
> {
> int[10] a;
> foreach (ref e; a)
> e = bar(x);
> }
>
> If bar is pure then you can safely transform this into:
>
> void foo(int x)
> {
> int[10] a;
> auto barx = bar(x);
> foreach (ref e; a)
> e = barx;
> }
>
> If bar is not pure then this transformation would be unsafe.
Yes, it will do something like that, though the loop will be unrolled
- and given that gdc supports vectorisation, I think that above
example will likely be vectorised too. So off the top of my head:
void foo(int x)
{
auto barx = bar(x);
vector(4) vect = { barx, barx, barx, barx };
*[&a] = vect;
*[&a+16] = vect;
a[9] = barx;
a[10] = barx;
}
Regards
--
Iain Buclaw
*(p < e ? p++ : p) = (c & 0x0f) + '0';
