On 11/29/2013 05:24 AM, Richard Biener wrote:
> On Thu, Nov 28, 2013 at 6:11 PM, Kenneth Zadeck
> <zadeck@naturalbridge.com> wrote:
>> This patch does three things in wide-int:
>>
>> 1) it cleans up some comments.
>> 2) removes a small amount of trash.
>> 3) it changes the max size of the wide int from being 4x of
>> MAX_BITSIZE_MODE_ANY_INT to 2x +1.   This should improve large muls and divs
>> as well as perhaps help with some cache behavior.
> @@ -235,8 +233,8 @@ along with GCC; see the file COPYING3.
>      range of a multiply.  This code needs 2n + 2 bits.  */
>
>   #define WIDE_INT_MAX_ELTS \
> -  ((4 * MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
> -   / HOST_BITS_PER_WIDE_INT)
> +  (((2 * MAX_BITSIZE_MODE_ANY_INT + HOST_BITS_PER_WIDE_INT - 1) \
> +    / HOST_BITS_PER_WIDE_INT) + 1)
>
> I always wondered why VRP (if that is the only reason we do 2*n+1)
> cannot simply use FIXED_WIDE_INT(MAX_BITSIZE_MODE_ANY_INT*2 + 1)?
> Other widest_int users should not suffer IMHO.  widest_int should
> strictly cover all modes that the target can do any arithmetic on
> (thus not XImode or OImode on x86_64).
>
> Richard.
>
>> ok to commit
enclosed is the code to change the large multiplies in tree-vrp as well 
as sets the size of the WIDE_INT_MAX_ELTS as we have discussed.

Bootstrapped and tested on x86-64.

ok to commit?

kenny