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Re: Higher level RTL issues
- To: Daniel Berlin <dan at cgsoftware dot com>
- Subject: Re: Higher level RTL issues
- From: law at redhat dot com
- Date: Mon, 22 Oct 2001 15:04:30 -0600
- cc: dnovillo at redhat dot com, gcc at gcc dot gnu dot org
- Reply-To: law at redhat dot com
In message <BF0CB0D7-C728-11D5-9F25-0030657B5340@cgsoftware.com>you write:
> > So how is this done when SSA names are not reflected in the IR?
> You can do the same thing.
> You just need names.
> If you look at the ssa-ccp patch i submitted, you'll note i added a
> unique id number to each ref, and use it in the following way to give an
> ssa name:
> For a phi or a def, the ssa name is the id number.
> For a use, the ssa name is the id number of the associated def.
> This gives you the same "name" an explicit renamed representation would
> give you, but we still haven't rewritten any code.
Right, but whenever you make this kind of transformation you have to scrurry
around and find all the uses the update the id number to point to the new
def. Ugh. How unpleasant. The beauty of a rewriting SSA is it just works.
> I'm assuming you keep the definitions/uses/phi links updated
> approriately, which is where the real pain lies.
No need for this kind of bookkeeping since the dominator opts happen
before we build those links.