SIMD benchmark

[Iain Buclaw]

On 16 January 2012 22:36, Iain Buclaw <ibuclaw at ubuntu.com> wrote:
> On 16 January 2012 21:57, Peter Alexander <peter.alexander.au at gmail.com> wrote:
>> On 16/01/12 8:56 PM, Iain Buclaw wrote:
>>>
>>> On 16 January 2012 19:25, Walter Bright<newshound2 at digitalmars.com>
>>>  wrote:
>>>>
>>>> On 1/16/2012 11:16 AM, Iain Buclaw wrote:
>>>>
>>>>>>
>>>>>> But don't worry, I'm not planning on working on that at the moment :-)
>>>>>
>>>>>
>>>>> Leave that sort of optimisation for the backend to handle please. ;-)
>>>>
>>>>
>>>>
>>>> Of course.
>>>>
>>>> I suspect Intel's compiler does that one, does gcc?
>>>>
>>>
>>> There's auto-vectorisation for for(), foreach(), and foreach_reverse()
>>> loops that I have written support for.  I am not aware of GCC
>>> vectorising anything else.
>>>
>>> example:
>>>
>>> int a[256], b[256], c[256];
>>> void foo () {
>>>   for (int i=0; i<256; i++)
>>>     a[i] = b[i] + c[i];
>>> }
>>>
>>
>> Unfortunately, if the function was this:
>>
>> void foo(int[] a, int[] b, int[] c) {
>>
>>  for (int i=0; i<256; i++)
>>    a[i] = b[i] + c[i];
>> }
>>
>> Then it can't vectorize due to aliasing.
>
> Compile with -fstrict-aliasing then?
>
> I could certainly play about with having this enabled by default, but
> I forsee there may be issues (maybe have it on for @safe code?)
>
>
> Regards
> --
> Iain Buclaw
>
> *(p < e ? p++ : p) = (c & 0x0f) + '0';

OK, have turned on strict aliasing by default for D2.  You should now
be able to vectorise loops that use locals and parameters. :-)


-- 
Iain Buclaw

*(p < e ? p++ : p) = (c & 0x0f) + '0';