On Tue, Aug 05, 2014 at 10:45:38AM +0200, Richard Biener wrote: > On Mon, Aug 4, 2014 at 3:04 PM, <tsaund...@mozilla.com> wrote: > > From: Trevor Saunders <tsaund...@mozilla.com> > > > > Hi, > > > > It used to be that edge_var_maps held pointers to embedded vectors, but > > now it holds vectors. This means that now instead of copying the > > address of the embedded vector from the table we keep a pointer into the > > table. However that's incorrect because we may expand the table when > > inserting new into the map in which case our pointer into the map points > > at freed memory. > > > > gcc/ > > > > * tree-ssa.c (redirect_edge_var_map_dup): copy the value in the > > map for old before inserting new. > > > > testing ongoing on x86_64-unknown-linux-gnu, ok? > > Umm... can you explore what it takes to instead store some kind of > indexes?
into what? > That is, how is the above not an issue for other 'head's that may be > live somewhere? what do you mean by other head's? Presumably nobody did something like void **p = pointer_map_contains (t, x); void **q = pointer_map_insert (t, y); *q = *p; because that would be broken, and that's the same problem we have here. So assuming I didn't break anything else nobody else uses a pointer into the table that they have after inserting elements. > Or can you restore what "used to be"? I thought I had to bail out early if the map didn't contain old, but when I actually look at the ddiff it looks like we delt with this before by just inserting new and then getting old so yeah I can just make things work more like they used to. Though maybe at some point we want to try and have less elements in the table with empty vectors. Trev > > Thanks, > Richard. > > > Trev > > > > --- > > gcc/tree-ssa.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c > > index 920cbea..b949d48 100644 > > --- a/gcc/tree-ssa.c > > +++ b/gcc/tree-ssa.c > > @@ -109,7 +109,11 @@ redirect_edge_var_map_dup (edge newe, edge olde) > > if (!head) > > return; > > > > - edge_var_maps->get_or_insert (newe).safe_splice (*head); > > + /* Save what head points at because if we need to insert new into the > > map we > > + may end up expanding the table in which case head will no longer > > point at > > + valid memory. */ > > + vec<edge_var_map> h = *head; > > + edge_var_maps->get_or_insert (newe).safe_splice (h); > > } > > > > > > -- > > 2.0.1 > >
