On December 26, 2014 4:50:33 PM CET, Bruce Momjian <br...@momjian.us> wrote:
>On Thu, Dec 25, 2014 at 11:57:29AM +0530, Abhijit Menon-Sen wrote:
>> Hi.
>> Here's a proposed patch to use CPUID at startup to determine if the
>> SSE4.2 CRC instructions are available, to use them instead of the
>> slice-by-8 implementation (posted earlier).
>> A few notes:
>> 1. GCC has included cpuid.h since 4.3.0, so I figured it was safe to
>>    use. It can be replaced with some inline assembly otherwise.
>> 2. I've also used the crc32b/crc32q instructions directly rather than
>>    using ".bytes" to encode the instructions; bintuils versions since
>>    2007 or so have supported them.
>> 3. I've included the MSVC implementation mostly as an example of how
>>    extend this to different compilers/platforms. It's written
>>    to the documentation for MSVC intrinsics, but I have not tested
>>    Suggestions/improvements are welcome.
>Uh, what happens if the system is compiled on a different CPU that it
>run on?  Seems we would need a run-time CPU test.

That's the cpuid thing mentioned above.


Please excuse brevity and formatting - I am writing this on my mobile phone.

Andres Freund                      http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:

Reply via email to