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From: "dberlin at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/38204] PRE for post dominating expressions
Date: Fri, 21 Nov 2008 16:57:00 -0000 [thread overview]
Message-ID: <20081121165538.18991.qmail@sourceware.org> (raw)
In-Reply-To: <bug-38204-1008@http.gcc.gnu.org/bugzilla/>
------- Comment #2 from dberlin at gcc dot gnu dot org 2008-11-21 16:55 -------
(In reply to comment #0)
> For this function:
> int test (int a, int b, int c, int g)
> {
> int d, e;
> if (a)
> d = b * c;
> else
> d = b - c;
> e = b * c + g;
> return d + e;
> }
>
> the multiply expression is moved to both branches of the "if", it would be
> better to move it before the "if". Intel's compiler does that.
>
Moving it before the if is a code size optimization that also happens to extend
the lifetime of the multiply.
So "better" is a relative term.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38204
next prev parent reply other threads:[~2008-11-21 16:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-20 17:00 [Bug middle-end/38204] New: " dann at godzilla dot ics dot uci dot edu
2008-11-21 6:43 ` [Bug middle-end/38204] " steven at gcc dot gnu dot org
2008-11-21 16:57 ` dberlin at gcc dot gnu dot org [this message]
2008-11-22 0:36 ` davidxl at gcc dot gnu dot org
2008-12-01 22:14 ` steven at gcc dot gnu dot org
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