On Thu, Nov 28, 2013 at 6:11 PM, Kenneth Zadeck
<zad...@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
