From: Mark Mendell <mendell@ca.ibm.com>
To: Mark Mitchell <mark@codesourcery.com>
Cc: Andrew_Pinski@playstation.sony.com, gcc <gcc@gcc.gnu.org>,
Hans-Peter Nilsson <hp@bitrange.com>,
Richard Guenther <richard.guenther@gmail.com>,
Russell_Olsen@playstation.sony.com,
trevor_smigiel@playstation.sony.com
Subject: Re: __builtin_expect for indirect function calls
Date: Mon, 07 Jan 2008 21:15:00 -0000 [thread overview]
Message-ID: <OFAFCA915C.26EC5659-ON852573C9.00745C20-852573C9.0074BBD2@ca.ibm.com> (raw)
In-Reply-To: <47812F74.3020905@codesourcery.com>
The frontends here would prefer to just implement __builtin_expect_call
(fp,foo), and leave __builtin_expect as it is now. We don't see a need for
a polymorphic __builtin_expect, as we are worried about backwards
compatibility.
A question was raised: Are side effects in the second parameter guaranteed
to be executed? Is it valid for a compiler to ignore any side effects?
Mark Mendell
TOBEY Team Lead
IBM Toronto Laboratory, 8200 Warden Ave, Markham, Ontario, Canada, L6G 1C7
Tel: 905-413-3485 Tie: 313-3485 Internet: mendell@ca.ibm.com
From: Mark Mitchell <mark@codesourcery.com>
To: Richard Guenther <richard.guenther@gmail.com>
Cc: trevor_smigiel@playstation.sony.com, Hans-Peter Nilsson <hp@bitrange.com>, gcc <gcc@gcc.gnu.org>,
Russell_Olsen@playstation.sony.com, Andrew_Pinski@playstation.sony.com, Mark Mendell/Toronto/IBM@IBMCA
Date: 06/01/2008 02:42 PM
Subject: Re: __builtin_expect for indirect function calls
Richard Guenther wrote:
>> What do people think? Do we have the leeway to change this? Or should
>> we add __builtin_expect2? Or add an -fno-polymorphic-builtin-expect?
>> Or...?
>
> I think we should simply make __builtin_expect polymorphic, but make sure
> to promote integral arguments with rank less than long to long.
I thought of that, but I hadn't suggested this idea because it seemed so
weird. Promoting to int would not be odd, but promoting to long is
weird. Anyhow, you're right; that's another option, and, despite
weirdness, plausible. I can't think of a way in which it changes
current behavior, unless you call __builtin_expect with a long long, and
that's probably not going to do what you expect right now anyhow.
--
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713
next prev parent reply other threads:[~2008-01-07 21:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-18 0:52 trevor_smigiel
2007-12-18 2:27 ` Jonathan Adamczewski
2007-12-22 3:42 ` Hans-Peter Nilsson
2007-12-26 19:10 ` Mark Mitchell
2008-01-03 23:36 ` trevor_smigiel
2008-01-05 5:44 ` Mark Mitchell
2008-01-05 10:40 ` Richard Guenther
2008-01-06 19:44 ` Mark Mitchell
2008-01-07 21:15 ` Mark Mendell [this message]
2008-01-08 15:36 ` Dave Korn
2008-01-08 15:51 ` Dave Korn
2008-01-03 23:46 ` trevor_smigiel
2008-01-06 20:42 Ross Ridge
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