> 2009/4/19 Jan Hubicka <hubi...@ucw.cz>: > >> On Sat, Apr 18, 2009 at 7:01 PM, Dave Korn > >> <dave.korn.cyg...@googlemail.com> wrote: > >> > > >> > Hi, > >> > > >> > I'm getting a stack overflow caused by *very* deep recursion while > >> > trying to > >> > build gnu/javax/swing/text/html/parser/HTML_401F.o in libjava, > >> > bootstrapping > >> > HEAD on i686-pc-cygwin. > >> > > >> > With the default per-thread stack size of 2MB, it crashes in > >> > tree_ssa_phiprop_1(), which by the time of the crash has recursed to a > >> > depth > >> > that I can actually honestly describe as "OVER 9000"! If I boost the > >> > stack to > >> > 4MB, I find that the recursion does actually bottom out at some point, > >> > since > >> > the compile completes, but I tested at 3MB and it crashed at a recursion > >> > depth > >> > of 13924. > >> > > >> > I know that boostrapping libjava is a tough job and pretty intensive on > >> > memory demands, but is this level of nesting actually to be expected, or > >> > has > >> > something gone astray? > >> > >> Well, this is one of the usual ways of iterating over the CFG, so this > >> is certainly > >> not unexpected. Maybe for some reason gsi is not scalarized and stack > >> usage > >> of that function is unusually high? > > > > There used to be rule that we should not expect CFG walk to fit in > > stack. I.e. all CFG walking needs to be written with explicit > > worklist/stack instead of using recursion. Perhaps it should enforce it > > here too? :) > > Well ... in this case it's likely the problem that propagate_with_phi is > inlined (single-use static function) and maybe other helpers of it too. > Maybe we should instead throttle inlining into functions that recurse? ;)
There is stack frame growth limit parameter for inliner, we can experiment with setting these lower. It seemed that it does not reduce performance, but since stack usage params was made primarily for kernel I didn't didn't care much to see if they can be trottled down for normal code. Trottling even lower for functions lying in SCC of cgraph seems good idea too. Honza > > Richard. > > > > > Honza > >
