Re: Trivial speedup to aliasing

[Jan Hubicka <jh at suse dot cz>]

> 
> On Jan 11, 2004, at 8:28 PM, Jan Hubicka wrote:
> 
> >>
> >>On Jan 11, 2004, at 7:21 PM, Jan Hubicka wrote:
> >>
> >>>
> >>>Hi,
> >>>about 3% of Gerald's application compile time is consumed by splay
> >>>tree walking
> >>>that comes from aliasing.  It seems to me that it is safe to replace
> >>>this by
> >>>trivial varray as alias sets are always allocated consetuctively.
> >>>With this
> >>>patch I can save almost all the overhead and get the lookup off the
> >>>profiles.
> >>>I also measured 2 seconds out of 2 minutes GCC component compile time
> >>>but it
> >>>may be noise.
> >>>
> >>>I noticed that varray.c requires GENERIC_PTR to be in GGC memory.
> >>>This looks
> >>>wrong to me that when we do GGC we need to know the type anyway.
> >>
> >>
> >>This is what GTY ((param_is ("<typename>"))) is for.
> >
> >Hmm, Zdenek noticed that too :)
> >
> >>
> >>There are VARRAY_GENERIC arrays with ggc'd things in them that need to
> >>be marked, so don't do this.
> >>We added a noggc counterpart on the tree-ssa branch.
> >>
> >>Personally, I don't like that generic_ptr is ggc_alloc'd either, but
> >>unless you fix all the GTY'd generic varrays that need to be marked,
> >>you can't do this.
> >Are there any to fix?
> 
> At least on tree-ssa, there is one,but that's not why it was originally 
> there.
> I believe it was originally there for PCH.
> >
> >But merging back nogcc counterpart from tree-ssa would make me happy
> >too.
> 
> I think maybe the noggc should be the default, and we should have a GC 
> counterpart.

I see, there are quite few uses of this on tree-ssa, many seems to be
safe to de-gtyize.
I am not sure how to proceed here.  If the patch is accepted for
mainline, I can simply swap the meanings on tree-ssa, so we won't get
merge headaches (so we will have VARRAY_GENERIC_GGC)

Honza
> >
> 
>