[PATCH 07/11] Add bitcount inlinesfor RTEMS. These are found in FREEBSDs types.h

[Kirspel, Kevin]

After doing some research, the GCC default __builtin_popcount functions are slower than the FREEBSD versions (roughly 3.5x slower according to some tests I saw online).  If someone adds the -mpopcnt compile option, then it means that there is a CPU instruction to perform the task.  I think we should do what FREEBSD has done.  Only use the built in functions if there is a CPU instruction to execute it.

I have posted a patch to newlib.

Kevin Kirspel
Electrical Engineer - Sr. Staff
Idexx Roswell
235 Hembree Park Drive
Roswell GA 30076
Tel: (770)-510-4444 ext. 81642
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Fax: (770)-510-4445

-----Original Message-----
From: Sebastian Huber [mailto:sebastian.huber at embedded-brains.de] 
Sent: Tuesday, May 16, 2017 9:28 AM
To: Kirspel, Kevin <Kevin-Kirspel at idexx.com>; devel at rtems.org
Subject: Re: [PATCH 07/11] Add bitcount inlinesfor RTEMS. These are found in FREEBSDs types.h

On 16/05/17 15:18, Kirspel, Kevin wrote:
> Sorry.  I pulled that header file from memory which these days is losing its effectiveness.  So, should we put the bitcount changes in sys/types.h like FREEBSD?
>
> If so, I will submit a patch tonewlib at sourceware.org.  How long does it take to get the patch reviewed by the newlib mailing list?

Between one day and four weeks. If its not included this week, then we can use the alternative.

Please add GCC support for these operations. I think the builtins are available since GCC 3.4.0.

--
Sebastian Huber, embedded brains GmbH

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