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Re: [tree-ssa] Copy propagation [patch]
- From: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>
- To: law at redhat dot com
- Cc: Diego Novillo <dnovillo at redhat dot com>, gcc-patches at gcc dot gnu dot org
- Date: 01 Mar 2003 02:00:49 +0100
- Subject: Re: [tree-ssa] Copy propagation [patch]
- References: <200303010045.h210ja5V004488@localhost.redhat.com>
Op za 01-03-2003, om 01:45 schreef law at redhat dot com:
> In message <20030301002257 dot GA27233 at tornado dot toronto dot redhat dot com>, Diego Novillo w
> rites:
> >I finally found time to adapt aldyh's copy propagation pass
> >(http://gcc.gnu.org/ml/gcc-patches/2002-11/msg01529.html). Not
> >surprisingly, this patch looks quite different from the original.
> >The original implementation was done before we rewrote the base
> >infrastructure.
---- 8< ----
> FWIW, you can do this essentially for free while building the SSA
> form, along with value numbering and simple copy propagations. In
> addition to being effectively free, you also get to cut down on the
> amount of code all the other SSA opts ever see.
You can cut down the copies during SSA form building, but we would still
need this as a separate pass to cleanup the garbage that PRE (and later
on GVN and VRP) may leave behind.
Greetz
Steven