Re: [boost] [GSoC]Bits and Ints

Subject: Re: [boost] [GSoC]Bits and Ints
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2010-04-10 15:31:55

On Thu, 8 Apr 2010, Andrew Sutton wrote:

>> Is there any other existing integral special functions that mentioned
>> in the second part? Where can I find them?
>>
>
> I'm not aware of any. Maybe Jeremiah can provide some additional references?

Most of the stuff is from the URL that is on the Wiki page; a lot of the 
stuff is fairly basic but part of the goal is to abstract special 
processor instructions that do the operations with the best performance 
(rotate instructions, conditional moves based on the carry bit, etc.). 
That covers items 1 and 7 from the second bulleted list under Bits & Ints. 
Sign extension and saturating arithmetic may also have special 
instructions, as might bit-reversed addition and similar operations, but 
portable versions would also be necessary for platforms that don't have 
special instructions.  Some more references are:

Chapter 8 of 
http://support.amd.com/us/Processor_TechDocs/40546-PUB-Optguide_3-11_5-21-09.pdf 
(for integer division by a repeated value)

http://graphics.stanford.edu/~seander/bithacks.html (we probably should 
have everything in here)

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.86.1801 (with the 
addition routines for interleaved integers using arbitrary masks)

A couple of new things to add to the list: generic versions of 
count-leading-zeros, count-trailing-zeros, population count, etc. that 
have gcc intrinsics (only for certain concrete types, and with different 
names for different types) and often special instructions.

-- Jeremiah Willcock