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From: Steven Bosscher <s.bosscher@student.tudelft.nl>
To: Diego Novillo <dnovillo@redhat.com>,
	Zdenek Dvorak <rakdver@atrey.karlin.mff.cuni.cz>
Subject: Re: [tree-ssa] Lazy updating of stmt operands
Date: Sun, 07 Dec 2003 22:20:00 -0000
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References: <20031207161929.GA10638@atrey.karlin.mff.cuni.cz> <20031207171454.GA12827@atrey.karlin.mff.cuni.cz> <1070818186.7334.30.camel@frodo.toronto.redhat.com>
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On Sunday 07 December 2003 18:29, Diego Novillo wrote:
> > > tree-dfa.c:compute_immediate_uses()
> >
> > Which needs to pass through every single statement in the program. Not
> > really terribly efficient.
>
> *shrug*, it's used by SSA-CCP.  Since def-use edges are only needed by
> some passes, I don't think it would be worth our while trying to
> maintain them in get_stmt_operands.

There are going to be more passes that need immediate uses.  Even a simple 
pass to kill redundant PHIs (say, after unswitching a loop) will have to go 
over _all_ statements to get the immediate uses of one or two statements.  It 
would be really nice if there were some way to keep this information 
up-to-date at all times...

Gr.
Steven