[tree-ssa] Do alias analysis after SSA. Improvements to PR8361.

[Diego Novillo]

On Wed, 2004-01-07 at 22:12, law@redhat.com wrote:

> Very cool.  Presumably the next step is using the nature of the SSA
> graph to provide a rudimentary context sensitive alias analysis?
> 
Ah, yes.  Now that I re-read my message I never quite specified what I
had in mind.  Yes, the next step is to walk use-def chains at pointer
dereference sites to collect points-to information.

In principle, the SSA web gives us points-to information for free.  It
all depends on how much walking we're willing to do on the use-def
links.  We could collect context sensitive points-to information by
keeping alias information tied to SSA names.  Alternately, we can
aggregate that into context insensitive sets per DECL.

> Or do you have other infrastructure that has to go in first?
>
The only other piece of infrastructure is the use-def chain walker,
which is just a few lines of code.  The big change was moving alias
analysis down.


Diego.