On Fri, Dec 26, 2014 at 04:52:58PM +0100, Andres Freund wrote: > 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 > >to > >> extend this to different compilers/platforms. It's written > >according > >> to the documentation for MSVC intrinsics, but I have not tested > >it. > >> Suggestions/improvements are welcome. > > > >Uh, what happens if the system is compiled on a different CPU that it > >is > >run on? Seems we would need a run-time CPU test. > > That's the cpuid thing mentioned above.
Oh, so cpuid is not a macro exported by the compiler but a C API. Good. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers