[Bug middle-end/38729] long time needed in tree canonical iv

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2009-06-20 17:01 -------
With MAX_DOMINATORS_TO_WALK zero and find_loop_niter_by_eval completely
disabled
(checking enabled compiler, built with -O0):

 tree iv optimization  :  11.12 ( 6%) usr   0.07 ( 5%) sys  12.02 ( 6%) wall  
59123 kB (20%) ggc

With just find_loop_niter_by_eval disabled:

 tree iv optimization  :  10.81 ( 6%) usr   0.05 ( 3%) sys  11.44 ( 6%) wall  
59123 kB (20%) ggc

so that's it.  Restricting find_loop_niter_by_eval to single-exit loops
if !flag_expensive_optimizations results in

 tree iv optimization  :  10.95 ( 6%) usr   0.04 ( 3%) sys  12.06 ( 6%) wall  
59123 kB (20%) ggc

I'll bootstrap & test a patch to do that.

Zdenek - if for one exit we cannot determine the number of executions,
shouldn't we return chrec_dont_know here instead of just examining the
other exits?


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2009-06-20 16:43:34         |2009-06-20 17:01:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38729