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Re: Question re: SSA Aggressive Dead Code Elimination
- To: <law at redhat dot com>
- Subject: Re: Question re: SSA Aggressive Dead Code Elimination
- From: Daniel Berlin <dan at www dot cgsoftware dot com>
- Date: Wed, 27 Jun 2001 08:53:03 -0400 (EDT)
- cc: <gcc at gcc dot gnu dot org>
On Wed, 27 Jun 2001, Daniel Berlin wrote:
> law@redhat.com writes:
>
> > I'm not sure which is the better solution.
>
> Oh, and BTW, the reason you are running into this problem is that
> you've changed the dominance frontier (by removing 0 as a dominator of
> 1) , and thus, changed the IDF, and thus, eliminated the need for a
> phi node there.
> I think, anyway.
>
> So it's not really valid SSA until you do something about the PHI node.
Of course, What I mean is that it's not a valid transformation to make.
Which you already knew.
It's obviously still valid SSA, just with a needless phi node.
In fact, my suggestion would be to attempt to remove the now useless phi
node, which should also solve the problem.