[Bug rtl-optimization/89115] compile time and memory hog

rguenth at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Wed Jan 30 13:23:00 GMT 2019


Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
The DSE thing is (of course) alias queries and there, find_base_term.
200 000 calls to check_mem_read_use result in 25 600 000 calls to
canon_true_dependence.  I suppose we could cache the result of find_base_term
and have a canon_true_dependence_with_bases.

Eventually DSE should just give up with too long next_local_store chains.

Btw, the plus_constant calls all originate from true_dependence_1 ending
up calling get_addr and that re-building RTL that must be there already
somehow.  Thus in the end it originates from the excessive number of
alias queries done by DSE.  Even that get_addr() part could be cached
though.  canon_true_dependence_with_bases_and_addrs.

Unfortunately --param max-dse-active-local-stores is a bail-out thing
so we need to cross a magic barrier which is somewhere between 1000 and

> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=5000 (default)
18.59user 1.03system 0:19.62elapsed 99%CPU (0avgtext+0avgdata
0inputs+9808outputs (0major+933497minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=2500
18.13user 1.09system 0:19.22elapsed 99%CPU (0avgtext+0avgdata
0inputs+9904outputs (0major+934009minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=2000
18.57user 0.98system 0:19.56elapsed 99%CPU (0avgtext+0avgdata
0inputs+9808outputs (0major+933789minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=1500
18.71user 1.01system 0:19.74elapsed 99%CPU (0avgtext+0avgdata
0inputs+9808outputs (0major+933920minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=1250
18.54user 0.94system 0:19.49elapsed 99%CPU (0avgtext+0avgdata
0inputs+9808outputs (0major+933435minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=1000
7.63user 0.22system 0:07.86elapsed 99%CPU (0avgtext+0avgdata
0inputs+9808outputs (0major+170563minor)pagefaults 0swaps
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=500
7.66user 0.24system 0:07.90elapsed 100%CPU (0avgtext+0avgdata
> /usr/bin/time /abuild/rguenther/obj/gcc/cc1 -quiet tagCircle49h12.i -O --param max-dse-active-local-stores=250
7.73user 0.16system 0:07.90elapsed 100%CPU (0avgtext+0avgdata
0inputs+9904outputs (0major+170918minor)pagefaults 0swaps

I am testing

Index: gcc/opts.c
--- gcc/opts.c  (revision 268383)
+++ gcc/opts.c  (working copy)
@@ -670,7 +670,16 @@ default_options_optimization (struct gcc
   /* For -O1 only do loop invariant motion for very small loops.  */
-     opt2 ? default_param_value (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP) : 1000,
+     opt2 ? default_param_value (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP)
+     : default_param_value (PARAM_LOOP_INVARIANT_MAX_BBS_IN_LOOP) / 10,
+     opts->x_param_values, opts_set->x_param_values);
+  /* For -O1 reduce the maximum number of active local stores for RTL DSE
+     since this can consume huge amounts of memory (PR89115).  */
+  maybe_set_param_value
+     opt2 ? default_param_value (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES)
+     : default_param_value (PARAM_MAX_DSE_ACTIVE_LOCAL_STORES) / 10,
      opts->x_param_values, opts_set->x_param_values);

   /* At -Ofast, allow store motion to introduce potential race conditions.  */

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