[Bug middle-end/39326] Segmentation fault with -O1, out of memory with -O2

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39326

--- Comment #54 from Richard Biener <rguenth at gcc dot gnu.org> ---
For the original testcase on trunk we get at -O1

 tree loop invariant motion:  37.20 (16%) usr   0.02 ( 1%) sys  37.20 (16%)
wall   12127 kB ( 1%) ggc
 dead store elim1        :  17.42 ( 7%) usr   0.04 ( 2%) sys  17.44 ( 7%) wall 
 28345 kB ( 3%) ggc
 dead store elim2        :  26.22 (11%) usr   0.00 ( 0%) sys  26.20 (11%) wall 
 18664 kB ( 2%) ggc
 combiner                :  15.36 ( 6%) usr   0.04 ( 2%) sys  15.39 ( 6%) wall 
 70073 kB ( 7%) ggc
 LRA hard reg assignment :  74.07 (31%) usr   0.02 ( 1%) sys  74.05 (31%) wall 
     0 kB ( 0%) ggc
 reload CSE regs         :  12.67 ( 5%) usr   0.00 ( 0%) sys  12.66 ( 5%) wall 
 13315 kB ( 1%) ggc
 TOTAL                 : 237.86             1.83           239.60            
999181 kB

so that's still slow (memory usage is peaking at about 1.5GB now, during RA).

tree LIM:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls   s/call   s/call  name    
  4.22    120.72     9.83   299080     0.00     0.00  ref_indep_loop_p_2(loop*, 
mem_ref*, bool)
  1.89    151.82     4.41 1712943886     0.00     0.00 
mem_refs_may_alias_p(mem
_ref*, mem_ref*, pointer_map_t**) [clone .constprop.60]
  0.21    197.02     0.48    12192     0.00     0.00 
force_move_till(tree_node*, tree_node**, void*)

at -O2 this will blow up completely as it then runs into the affine-based
disambiguation.