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Re: [tree-ssa] Fix make_goto_expr_edges for computed gotos
- From: law at redhat dot com
- To: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
- Cc: Diego Novillo <dnovillo at redhat dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 21 Aug 2003 22:34:37 -0600
- Subject: Re: [tree-ssa] Fix make_goto_expr_edges for computed gotos
- Reply-to: law at redhat dot com
In message <20030820172358.GA29792@atrey.karlin.mff.cuni.cz>, Zdenek Dvorak wri
tes:
>On tree-ssa-cfg I remove the ordinary labels instead, redirecting the
>jumps to the special label. I am not quite sure what you mean by
>"penalizing" -- I don't think it affects any optimizations.
Edges for nonlocal gotos and the like are abnormal edges and we inhibit certain
optimizations in the presence of abnormal edges.
For example if either operand of a copy (either an explicit one or an
implicit one from a PHI node) is used as a PHI alternative associated
with an abnormal edge, then the copy can not be propagated (as doing so
may require the out-of-ssa pass to insert a copy on an abnormal critical
edge, which is bloody hard).
jeff