Trivial speedup to aliasing

[Daniel Berlin]

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.

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.