------- Comment #40 from amylaar at gcc dot gnu dot org 2006-08-24 20:50
-------
(In reply to comment #37)
> For a proper patch, the number should of course be a PARAM and I think using
> bitmap_count_bits penalizes the common case too much (walking the whole bitmap
> is cache expensive even for small bitmaps).
How about:
- if (vr && vr->equiv)
+ if (vr && vr->equiv && vr->equiv->first
&& (!vr->equiv->first->next
|| bitmap_count_bits (vr->equiv) < VRP_EQUIVALENCE_THRESHOLD)))
bitmap_ior_into (equiv, vr->equiv);
The 0 bit case is sped up, and the 1 bit case is guaranteed to only need two
pointer dereferences to check that there are not too many bits.
Other small bit numbers should still have a high likelyhood to he handled
without a bitmap_count_bits call.
The quick & dirty check might allow more than VRP_EQUIVALENCE_THRESHOLD
bits through if they are tightly packed, but that is still imited to 64
for a host with 32 bit longs, 128 for a host with 64 bit longs.
--
amylaar at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |amylaar at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19097
