Re: wide-int, cfg

[Mike Stump <mikestump at comcast dot net>]

On Nov 25, 2013, at 2:57 AM, Richard Biener <richard.guenther@gmail.com> wrote:
> On Sat, Nov 23, 2013 at 8:21 PM, Mike Stump <mikestump@comcast.net> wrote:
>> Richi has asked the we break the wide-int patch so that the individual port and front end maintainers can review their parts without have to go through the entire patch.    This patch covers the cfg code.
>> 
>> Ok?
> 
> Hmm, this is an example of a wide_int (a widest_int) being used inside
> a structure with long lifetime.  With the patch there are two of those
> per loop plus up to one per statement in a loop body (quadratic in
> the loop depth).


> Now, for the number-of-iterations stuff I really would like to keep things
> cheaper in some way or another.  Shrinking MAX_BITSIZE_MODE_ANY_INT
> would be the easiest improvement for x86_64.

> That said, I'd like this to be addressed.

The port can limit the size like so:

/* Keep the OI and XI modes from confusing the compiler into thinking
   that these modes could actually be used for computation.  They are
   only holders for vectors during data movement.  */
#define MAX_BITSIZE_MODE_ANY_INT (128)

and that is now done on x86.

Ok?

A copy of the patch is below (unchanged)...

Attachment: wide-int-cfg.diffs.txt
Description: Text document