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Re: [tree-ssa] reaching def. question
- From: Diego Novillo <dnovillo at redhat dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Devang Patel <dpatel at apple dot com>, "gcc at gcc dot gnu dot org list" <gcc at gcc dot gnu dot org>
- Date: Tue, 16 Mar 2004 19:36:32 -0500
- Subject: Re: [tree-ssa] reaching def. question
- Organization: Red Hat Canada
- References: <200403170027.i2H0RtZU001850@speedy.slc.redhat.com>
On Tue, 2004-03-16 at 19:27, law@redhat.com wrote:
> Which is not a safe thing to do if you've done things like copy propagation
> since you can have overlapping lifetimes.
>
We do this all the time. Passes just mark the variables they want to be
renamed and the SSA renamer is run as a cleanup.
> You also have to be damn careful about marking something to be rewritten
> which is used in a mixed PHI node. ie
>
> a_3 = PHI (a_2, b_1)
>
> Marking just a or b to be written is a recipe for disaster.
>
More context, with concrete examples, please. Are you talking about
copyprop *while* doing if-conversion?
Diego.