From: Michael S. Zick <mszick@goquest.com>
To: kenner@vlsi1.ultra.nyu.edu (Richard Kenner), dnovillo@redhat.com
Cc: gcc@gcc.gnu.org
Subject: Re: [tree-ssa] Out of SSA status and issues
Date: Tue, 13 May 2003 15:08:00 -0000 [thread overview]
Message-ID: <03051308584200.00935@wolf686> (raw)
In-Reply-To: <10305131322.AA13680@vlsi1.ultra.nyu.edu>
On Tuesday 13 May 2003 08:22 am, Richard Kenner wrote:
> I see nothing wrong in replacing 'i + 9' with '*p + 9'. It would
> probably not be efficient, but I can't see it being wrong.
>
> If an optimizer pessimizes the code, I'd consider that "wrong".
>
> This isn't a machine-dependent issue: with CPU speeds the way they are,
> a memory reference is *always* many times more expensive than an addition.
Nice generalization, but only relevant while considering '*p' to be an
expression.
Consider instead that '*p' is just the name given a register's
contents. Neither 'i' nor '9' are processor internal. Both are external
to the cpu. The memory reference for 'i' is source code implicit, the memory
reference for '*p' is source code explicit.
Mike
next prev parent reply other threads:[~2003-05-13 15:08 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-13 13:17 Richard Kenner
2003-05-13 13:27 ` Diego Novillo
2003-05-13 13:40 ` Michael Matz
2003-05-13 15:08 ` Michael S. Zick [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-05-13 15:23 Richard Kenner
2003-05-13 18:50 ` Geoff Keating
2003-05-13 23:28 ` Michael S. Zick
2003-05-17 17:19 ` Michael S. Zick
2003-05-13 13:42 Richard Kenner
2003-05-12 14:42 Andrew MacLeod
2003-05-12 15:38 ` Diego Novillo
2003-05-12 15:57 ` Andrew MacLeod
2003-05-12 16:05 ` Michael Matz
2003-05-12 16:10 ` Andrew MacLeod
2003-05-12 16:16 ` law
2003-05-12 17:08 ` law
2003-05-12 17:12 ` Andrew MacLeod
2003-05-12 17:26 ` law
2003-05-12 18:57 ` Andrew MacLeod
2003-05-13 9:07 ` Michael Matz
2003-05-13 12:42 ` Diego Novillo
2003-05-13 12:50 ` Andrew MacLeod
2003-05-13 13:05 ` Diego Novillo
2003-05-13 13:29 ` Andrew MacLeod
2003-05-13 13:57 ` Diego Novillo
2003-05-13 12:57 ` Michael Matz
2003-05-13 13:11 ` Diego Novillo
2003-05-13 13:18 ` Andrew MacLeod
2003-05-14 17:19 ` Jan Vroonhof
2003-05-14 18:05 ` Andrew MacLeod
2003-05-14 18:33 ` Diego Novillo
2003-05-14 19:11 ` Daniel Berlin
2003-05-13 15:01 ` Daniel Berlin
2003-05-13 12:33 ` Diego Novillo
2003-05-13 12:49 ` Andrew MacLeod
2003-05-13 12:58 ` Diego Novillo
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