[Bug tree-optimization/28868] [4.0/4.1/4.2/4.3 Regression] Not elimintating the PHIs which have the same arguments

[dberlin at dberlin dot org]

------- Comment #11 from dberlin at gcc dot gnu dot org  2007-11-04 19:24 -------
Subject: Re:  [4.0/4.1/4.2/4.3 Regression] Not elimintating the PHIs which have
the same arguments

On 4 Nov 2007 15:45:59 -0000, rguenth at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #10 from rguenth at gcc dot gnu dot org  2007-11-04 15:45 -------
> FRE doesn't replace a SSA_NAME with another SSA_NAME


Also true. It will only replace non-ssa names with ssa-names.

This is to avoid lengthening the range of variables.

Replacing ssa names with other ssa names willy-nilly is not always a
win.  We eventually ended up with heuristics to not change loop depths
of ssa names, etc.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28868