------- Comment #9 from rguenther at suse dot de 2009-11-03 12:21 ------- Subject: Re: imit-structnest.c fails due to O(n^2) memory usage in record_component_alias
On Tue, 3 Nov 2009, bonzini at gnu dot org wrote: > ------- 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?) Yes, they all form a forest. It shouldn't pessimize anything to enforce this. > 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. Right. Richard. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35608
