On Thu, 2006-12-21 at 12:21 -0500, Daniel Berlin wrote: > On 12/21/06, Diego Novillo <[EMAIL PROTECTED]> wrote: > > Robert Kennedy wrote on 12/21/06 11:37: > > > > > The situation is that some SSA_NAMEs are disused (removed from the > > > code) without being released onto the free list by > > > release_ssa_name(). > > > > > Yes, it happens if a name is put into the set of names to be updated by > > update_ssa. > > > > After update_ssa, it should be true that every SSA name with no > > SSA_NAME_DEF_STMT is in the free list. > > In this case this isn't true, because we have code that orphans ssa > names without releasing them. > I'm sure Robert will explain further details in a few moments :) True. But remember, the stated purpose of the SSA_NAME recycling code was _not_ to track every SSA_NAME that went "dead" and recycle it, but instead to get the majority of them (and to ultimately save memory by recycling them). Orphan SSA_NAME were always expected.
If we wanted to add a new policy that all dead SSA_NAMEs must be released to the recycling code, then that's fine, I'm not going to object. Alternately we can revisit the entire recycling question as well -- things have changed significantly since that code was written and I've speculated that the utility of the recycling code has diminished, possibly to the point of being a useless waste of time and code. The last obvious alternative I see is to stop chaining free nodes using the TREE_CHAIN field. That at least avoids the sharing between TREE_CHAIN and SSA_NAME_DEF_STMT which often causes problems. The downside is given an SSA_NAME it still won't be obvious if it is an orphan or still in use. Jef
