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Re: pr14627
- From: Steven Bosscher <stevenb at suse dot de>
- To: gcc-patches at gcc dot gnu dot org, law at redhat dot com
- Date: Wed, 13 Apr 2005 08:25:32 +0200
- Subject: Re: pr14627
- Organization: SUSE Labs
- References: <1113366530.9344.21.camel@localhost.localdomain>
On Wednesday 13 April 2005 06:28, Jeffrey A Law wrote:
> This patch implements an const/copy unpropagation pass.
FYI this pass was discussed in a long conversation on IRC a couple
of days ago. This came up because not only DOM, but also VRP can
cause this problem. The fundamental problem appears to be that we
allow constants as PHI arguments. When DOM was the only working
SSA pass, perhaps doing this made a lot of sense. But now, we need
this kind of passes to undo the damage later on. Perhaps it still
is easier to just allow only SSA names as PHI arguments, and look
at their SSA_NAME_VALUE if you want to know the value of the PHI
argument. That would make your pass unnecessary.
Gr.
Steven