[tree-ssa] Lazy updating of stmt operands

[Andrew MacLeod]

On Thu, 2003-12-11 at 17:30, Zdenek Dvorak wrote:
> Hello,
> 
>
> > While it's nice to think about a world where you always have immediate uses,
> > you end up with FUD chains if you do that -- with ultimately a tangled nest
> > of pointers that is bloody impossible to work with in the real world.
> 
> here is the patch.  It increases time for compiling preprocessed gcc
> sources from 3m43.734s to 3m47.967s.  It does not use interface of
> immediate uses, since that is not well suited for updating; instead it
> just keeps lists of uses for each ssa name.  The old interface and ccp
> that uses it are not changed by the patch, so in fact the cost would
> be a bit smaller.

More interesting is the time effectit has on larger C++ cases like
Geralds where we already have memory problem we are trying to resolve.
Thats where it was a significant issue for CCP in the system swap time.

Andrew