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Nested libcalls (was: Re: RFC: SMS problem with emit_copy_of_insn_after copying REG_NOTEs)
- From: Steven Bosscher <stevenb dot gcc at gmail dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: Jan Hubicka <jh at suse dot cz>, Andrew Pinski <pinskia at physics dot uc dot edu>, Ian Lance Taylor <iant at google dot com>, Vladimir Yanovsky <volodyan at gmail dot com>, Jan Hubicka <hubicka at ucw dot cz>, gcc at gcc dot gnu dot org, Vladimir Yanovsky <yanov at il dot ibm dot com>, Ayal Zaks <zaks at il dot ibm dot com>, zadeck at naturalbridge dot com
- Date: Sun, 31 Dec 2006 02:05:02 +0100
- Subject: Nested libcalls (was: Re: RFC: SMS problem with emit_copy_of_insn_after copying REG_NOTEs)
- References: <200612302207.kBUM7aG8023853@localhost.localdomain> <200612302214.kBUMEt3P025579@localhost.localdomain> <20061230235952.GC28965@kam.mff.cuni.cz>
On Sunday 31 December 2006 00:59, Jan Hubicka wrote:
> > Also I should mention, this also fixes a possible bug with libcalls that
> > are embedded in one another. Before we were just assuming if we have a
> > REG_RETVAL, then the previous REG_LIBCALL would be the start of the
> > libcall but that would be incorrect with embedded libcalls.
> We should not have nested libcalls at all. One level of libcalls is
> painful enough and we take care to not do this.
It's unclear whether we can have nested libcalls or not. We expect them
in some places (especially, see libcall_stack in gcse.c:local_cprop_pass)
but are bound to fail miserably in others.
This is something I've been wondering for a while. Maybe someone can
give a definitive answer: Can libcalls be nested, or not?