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Re: birthpoints in rtl.
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: Kenneth Zadeck <zadeck at naturalbridge dot com>
- Cc: Diego Novillo <dnovillo at google dot com>, Steven Bosscher <stevenb dot gcc at gmail dot com>, gcc <gcc at gcc dot gnu dot org>, "Bonzini, Paolo" <bonzini at gnu dot org>, "Park, Seongbae" <seongbae dot park at gmail dot com>, Ian Lance Taylor <iant at google dot com>, Richard Sandiford <rsandifo at nildram dot co dot uk>
- Date: Sat, 1 Mar 2008 11:13:15 +0100
- Subject: Re: birthpoints in rtl.
- References: <47C5EF2A.email@example.com> <47C6B132.firstname.lastname@example.org> <47C88C6B.email@example.com> <firstname.lastname@example.org> <47C89EC3.email@example.com> <47C8B3BB.firstname.lastname@example.org>
> I am leaning to just adding noop moves at the birthpoints (dominance
> frontiers) as real noop move insns in the streams in the passes that use
> ud or du chains. The back end is tolerant of noop moves and without
while I am with Diego that would preffer PHI nodes on side especially in
FUD chain where rest of your SSA is on side too. But if we go with the
extra instruction scheme, I think you are much better to use RTL USE
instruction. The moves are generated by target machinery and can do
funny things, like clobbering flags or whatever. USEs are transparent