From: Diego Novillo <dnovillo@redhat.com>
To: Jason Merrill <jason@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [tree-ssa] CCP and variable reference fixes [patch]
Date: Thu, 07 Nov 2002 11:48:00 -0000 [thread overview]
Message-ID: <20021107194832.GA3511@tornado.toronto.redhat.com> (raw)
In-Reply-To: <wvlptth1gua.fsf@prospero.boston.redhat.com>
On Thu, 07 Nov 2002, Jason Merrill wrote:
> On Thu, 7 Nov 2002 07:36:17 -0500, Diego Novillo <dnovillo@redhat.com> wrote:
>
> > - Removes unnecessary fields from tree_ref structure. We don't
> > need to keep pointers into the expression nor operand for each
> > reference. This makes it possible for a pass to replicate a
> > statement and replace references from the original statement
> > into the copy.
>
> When rth and I were talking about this later, it occurred to me that if we
> can have an expression with uses of two different defs of the same variable
> in a single stmt, then we do need a use to refer directly to its instance
> of the variable within the statement.
>
Impossible. If you have two uses of the same variable coming
from different definitions, then your SSA information is
completely broken. It's actually not possible for the SSA
builder to create such a thing (it keeps a single instance of
'current definition').
Diego.
next prev parent reply other threads:[~2002-11-07 19:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-07 4:36 Diego Novillo
2002-11-07 8:34 ` Jason Merrill
2002-11-07 8:59 ` Daniel Berlin
2002-11-07 11:48 ` Diego Novillo [this message]
2002-11-07 14:08 ` Jason Merrill
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