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From: Jason Moxham <jlm@maths.soton.ac.uk>
To: gcc@gcc.gnu.org
Subject: aliasing
Date: Sat, 21 Aug 1999 09:23:00 -0000	[thread overview]
Message-ID: <199908211622.RAA18934@malone.maths.soton.ac.uk> (raw)

I have a C++ ( really a C prog with a couple of overloaded fn's )
program which I'm fairly sure breaks the strict aliasing rules of
Gcc-2.95.1 

Where can find a copy of what these rules are , so I can fix my code ?


For a temporary fix I added -fno-strict-aliasing to the options and
expected a performance drop . However the program now runs 1% faster ???
(I assure you 1% is not a trival amount)

Using Slackware 3.9 + gcc 2.95.1 on AMD K6(x86)
options -O3 -fno-exceptions -funroll-loops -march=k6
-fomit-frame-pointer -ffast-math   ... etc

I can send 
source(100K) + exe's(50K) + data  etc.. 


Jason Moxham
jlm@maths.soton.ac.uk

WARNING: multiple messages have this Message-ID

From: Jason Moxham <jlm@maths.soton.ac.uk>
To: gcc@gcc.gnu.org
Subject: aliasing
Date: Tue, 31 Aug 1999 23:20:00 -0000	[thread overview]
Message-ID: <199908211622.RAA18934@malone.maths.soton.ac.uk> (raw)
Message-ID: <19990831232000.w8EotH24xaxDquCaqvGjggVUYwypIWNzr3qcoJMnXqs@z> (raw)

I have a C++ ( really a C prog with a couple of overloaded fn's )
program which I'm fairly sure breaks the strict aliasing rules of
Gcc-2.95.1 

Where can find a copy of what these rules are , so I can fix my code ?


For a temporary fix I added -fno-strict-aliasing to the options and
expected a performance drop . However the program now runs 1% faster ???
(I assure you 1% is not a trival amount)

Using Slackware 3.9 + gcc 2.95.1 on AMD K6(x86)
options -O3 -fno-exceptions -funroll-loops -march=k6
-fomit-frame-pointer -ffast-math   ... etc

I can send 
source(100K) + exe's(50K) + data  etc.. 


Jason Moxham
jlm@maths.soton.ac.uk

             reply	other threads:[~1999-08-21  9:23 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
1999-08-21  9:23 Jason Moxham [this message]
1999-08-21  9:46 ` aliasing Mark Mitchell
1999-08-31 23:20   ` aliasing Mark Mitchell
1999-08-31 23:20 ` aliasing Jason Moxham
2024-03-18  7:03 aliasing Martin Uecker
2024-03-18  8:26 ` aliasing Richard Biener
2024-03-18 10:55   ` aliasing Martin Uecker
2024-03-18 11:56     ` aliasing Martin Uecker
2024-03-18 13:21       ` aliasing Richard Biener
2024-03-18 15:13         ` aliasing Martin Uecker
2024-03-18  9:00 ` aliasing David Brown
2024-03-18 10:09   ` aliasing Jonathan Wakely
2024-03-18 11:41   ` aliasing Martin Uecker
2024-03-18 13:29     ` aliasing David Brown
2024-03-18 13:54       ` aliasing Andreas Schwab
2024-03-18 16:46         ` aliasing David Brown
2024-03-18 16:55           ` aliasing David Brown
2024-03-18 15:00       ` aliasing Martin Uecker
2024-03-18 17:11         ` aliasing David Brown

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