From: Joe Buck <jbuck@synopsys.com>
To: Richard Henderson <rth@redhat.com>,
Diego Novillo <dnovillo@redhat.com>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: [tree-ssa] copy propagation and the abstraction penalty
Date: Thu, 15 May 2003 22:51:00 -0000 [thread overview]
Message-ID: <20030515155125.A19245@synopsys.com> (raw)
In-Reply-To: <20030515154829.A19150@synopsys.com>; from Joe.Buck@synopsys.COM on Thu, May 15, 2003 at 03:48:29PM -0700
On Thu, May 15, 2003 at 03:48:29PM -0700, Joe Buck wrote:
> On Thu, May 15, 2003 at 03:17:48PM -0700, Richard Henderson wrote:
> > Indeed. And for this case I definitely think it's the right thing to do.
> >
> > IMO constant propagation should be able to take
> >
> > T.8_2 = &<UVa150>;
> > {
> > struct complex * const this;
> >
> > this_3 = (struct complex * const)T.8_2;
> > {
> > this->re = 1.0e+0;
> >
> > and turn it into
> >
> > (&<UVa150>)->re = 1.0e+0
> >
> > which folds to
> >
> > <UVa150>.re = 1.0e+0
> >
> > At which point we have no aliasing problem, and a subsequent round
> > of constant propagation ought to be able to send 1.0e+0 to its
> > destination.
>
> That helps this case, but in many other cases the content of the temporary
> struct's field will be a variable, and we would still want to copy-propagate.
Sigh. Sorry Richard: of course the addresses are constant; I was focusing
on the 1.0e0 constant. As a Gilda Radner character used to say, never
mind.
prev parent reply other threads:[~2003-05-15 22:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-14 22:45 Joe Buck
2003-05-15 3:15 ` Andrew Pinski
2003-05-15 14:10 ` Diego Novillo
2003-05-15 17:09 ` Joe Buck
2003-05-15 17:28 ` Joe Buck
2003-05-15 18:01 ` Daniel Berlin
2003-05-15 22:20 ` Richard Henderson
2003-05-15 22:48 ` Joe Buck
2003-05-15 22:51 ` Joe Buck [this message]
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