Re: [PATCH] Simple optimization for MASK_STORE.

[Mike Stump <mikestump@comcast.net>]

On Nov 10, 2015, at 6:56 AM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
> 2015-11-10 17:46 GMT+03:00 Richard Biener <richard.guenther@gmail.com>:
>> On Tue, Nov 10, 2015 at 1:48 PM, Ilya Enkovich <enkovich.gnu@gmail.com> wrote:
>>> 2015-11-10 15:33 GMT+03:00 Richard Biener <richard.guenther@gmail.com>:
>>>> On Fri, Nov 6, 2015 at 2:28 PM, Yuri Rumyantsev <ysrumyan@gmail.com> wrote:
>>>>> Richard,
>>>>> 
>>>>> I tried it but 256-bit precision integer type is not yet supported.
>>>> 
>>>> What's the symptom?  The compare cannot be expanded?  Just add a pattern then.
>>>> After all we have modes up to XImode.
>>> 
>>> I suppose problem may be in:
>>> 
>>> gcc/config/i386/i386-modes.def:#define MAX_BITSIZE_MODE_ANY_INT (128)
>>> 
>>> which doesn't allow to create constants of bigger size.  Changing it
>>> to maximum vector size (512) would mean we increase wide_int structure
>>> size significantly. New patterns are probably also needed.
>> 
>> Yes, new patterns are needed but wide-int should be fine (we only need to create
>> a literal zero AFACS).  The "new pattern" would be equality/inequality
>> against zero
>> compares only.
> 
> Currently 256bit integer creation fails because wide_int for max and
> min values cannot be created.
> It is fixed by increasing MAX_BITSIZE_MODE_ANY_INT, but it increases
> WIDE_INT_MAX_ELTS
> and thus increases wide_int structure. If we use 512 for
> MAX_BITSIZE_MODE_ANY_INT then
> wide_int structure would grow by 48 bytes (16 bytes if use 256 for
> MAX_BITSIZE_MODE_ANY_INT).

Not answering for Richard, but the design of wide-int was that though the temporary space would grow, trees and rtl would not.  Most wide-int values are short lived.