[tree-ssa] Lazy updating of stmt operands

[Steven Bosscher]

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