------- Comment #8 from bonzini at gnu dot org 2009-11-03 12:18 -------
Memory allocation is O(n^2) in the nesting of the structures: when changing
LIM4 from 6 to 7 invocations of the lower-level, memory goes from 583976 KB to
798116 KB (which is 1.366 times more, almost exactly a factor of (7/6)^2).
The culprit is record_component_aliases which creates a subset relationship
from each structure to each containing structure. Maybe we could reuse the
et-forest here since these subset relationships form a forest (do all of them
have this property? would we pessimize a lot by enforcing that even when it is
conservative?)
I suppose the bug has always been there since alias.c was introduced, it's just
that previously an unused struct did not call record_component_aliases.
--
bonzini at gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu dot
| |org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Keywords| |compile-time-hog, memory-hog
Last reconfirmed|0000-00-00 00:00:00 |2009-11-03 12:18:41
date| |
Summary|gcc.c- |imit-structnest.c fails due
|torture/compile/limits- |to O(n^2) memory usage in
|structnest.c fails -O2 -Os |record_component_alias
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35608
