[Fwd: [PATCH, RFC] Expose target addressing modes before expand (revised)]

[William J. Schmidt]

Steven and Jeff, thanks for the pointers.  The full dominator walk with
callbacks is probably overkill; I will probably model my code after the
eliminate_degenerate_phis pass in ssa-tree-dom.c, which just walks the
dominator tree in a simple manner.

On Thu, 2011-02-24 at 14:55 -0700, Jeff Law wrote:
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> On 02/24/11 14:46, Steven Bosscher wrote:
> > On Thu, Feb 24, 2011 at 8:12 PM, Jeff Law <law@redhat.com> wrote:
> >> On 02/24/11 11:24, William J. Schmidt wrote:
> >>> It occurs to me that it would be easy to expand the CSE by saving the
> >>> hash table for each block, rather than throwing it out immediately.
> >>> Each block could then seed its hash table with the data from its
> >>> immediate dominator.  This would avoid relying on a downstream global
> >>> CSE to clean up afterwards.
> >> Yup.  That's standard stuff for CSE.  The existing code in GCC
> >> (tree-ssa-dom.c and cse.c) already do this.
> > 
> > Right, and this new pass could re-use at least the dominator tree
> > walker (domwalk.[ch]?).
> domwalk can be pretty heavyweight, but for what it sounds like William
> is doing, it might make sense.
> 
> William would also find code in tree-ssa-dom that manages select removal
> of expressions from the various tables as the walker leaves blocks
> during the domwalk.  That probably makes more sense than saving the hash
> table :-)

Yes, after thinking through it a little more, I'll do something along
these lines.  It should be simple enough to keep only the active
expressions in my alloc_pool as I walk down and up the tree.

Oh, and please call me Bill. :)

Thanks again!

> 
> jeff
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