Re: Portability: common-src/amcrc32chw.c & config/amanda/amanda_configure.m4

amanda detect at run time if the sse4.2 instruction are available and 
use them only if they are available.
different code is used if the sse4.2 instruction are not available.
What's wrong with that?

If I understand, you want an option to completely disable sse4.2?
You do not want newer CPU to use sse4.2
I don't understand since amanda detect sse4.2 at run time.

Jean-Louis


On 03/01/17 02:45 PM, Eric Schnoebelen wrote:
> Jean-Louis Martineau writes:
> - What is the issue you get?
>
> NetBSD does not provide __builtin_ia32_* in any library.  In
> experimentation, I did find that if -msse4.2 is provided to gcc,
> the various __builtin_ia32_ functions do appear.
>
> However, pkgsrc attempts to build for lowest common denominiator
> systems when building for distribution (hence, not using SSE* in
> any form on x86 systems.)
>
> Individual users can add additional build flags for their specific
> systems, but the distribution builds must be portable for all
> systems of a given processor/OS architecture.
>
> - I think I can replace the #ifdef line with:
> - #ifdef __SSE_4_2_
> -
> - Because if __SSE_4_2_ is defined then the __builtin_ia32_crc32* function
> - must be defined
>
> Depending on a compiler specific internal macro definition seems
> fraught with danger.  Imagine the case of xycc (random non-gcc
> compiler) defining __SSE_4_2_ for some purpose, but not
> providing these particular functions.  Feature testing for the
> functions used is almost always a better idea.
If the xycc compiler define __SSE4_2__ for a different meaning then that 
compiler is broken.
Both gcc and clang define it
.
>
> Do you have access to a non-Linux, non-x86, non-gcc system for
> development/testing? (not all the world is linux/x86/gcc. :D )
>
> Reflecting over lunch, perhaps it would be better to depend upon
> OpenSSL/GnuTLS/LibreSSL to provide the CRC functions desired.
> Those libraries would provide the appropriate machine specific
> optimized versions for every platform, leaving Amanda more
> system/compiler agnostic and portable.
>
> - On 02/01/17 02:53 PM, Eric Schnoebelen wrote:
> - > Issue: Attempting to use gcc __builtin functions without
> - > appropriate feature tests.  Not all platforms use gcc, and not
> - > all gcc platforms provide the __builtin_ia32_* functions (as not
> - > all gcc platforms are necessarily x86_*)
> - >
> - > Solution: add feature test macros for the __builtin_ia32_*
> - > functions being used, and wrapper their use with the feature
> - > test macro.
> - >
> - > patches inline and as attachments
> - >
> - >
> - > $NetBSD$
> - >
> - > Add tests for the gcc __builtin_ia32_crc32[qdsu]i functions.
> - >
> - > --- config/amanda/amanda_configure.m4.orig=092016-11-23 16:11:15.000000000 +0000
> - > +++ config/amanda/amanda_configure.m4
> - > @@ -364,8 +364,9 @@ ICE_CHECK_DECL(strcasecmp,string.h strin
> - >   ICE_CHECK_DECL(euidaccess,unistd.h)
> - >   ICE_CHECK_DECL(eaccess,unistd.h)
> - >   ICE_CHECK_DECL(clock_gettime,time.h)
> - > -AC_CHECK_FUNCS(getservbyname_r)
> - > +ICE_CHECK_DECL(getservbyname_r, netdb.h)
> - >   AC_CHECK_FUNCS(sem_timedwait)
> - > +AC_CHECK_FUNCS(__builtin_ia32_crc32qi __builtin_ia32_crc32di __builtin_ia32_crc32si __builtin_ia32_crc32hi)
> - >
> - >   #
> - >   # Devices
> - >
> - >
> - > $NetBSD$
> - >
> - > Change the test to use a feature test macro for the existance of the
> - > builtin functions being used.
> - >
> - > (bad programmer, using compiler internal routines in public code.)
> - >
> - > --- common-src/amcrc32chw.c.orig=092016-11-23 16:11:16.000000000 +0000
> - > +++ common-src/amcrc32chw.c
> - > @@ -29,7 +29,11 @@
> - >   #include <amutil.h>
> - >   #include <amcrc32chw.h>
> - >
> - > -#if defined __GNUC__ && GCC_VERSION > 40300 && (defined __x86_64__ || defined __i386__ || defined __i486__ || defined __i586__ || defined __i686__)
> - > +#if defined HAVE___BUILTIN_IA32_CRC32QI && \
> - > +	defined HAVE___BUILTIN_IA32_CRC32DI && \
> - > +	defined HAVE___BUILTIN_IA32_CRC32SI && \
> - > +	defined HAVE___BUILTIN_IA32_CRC32UI
> - > +
> - >   #define POLY 0x82F63B78
> - >
> - >   /* Multiply a matrix times a vector over the Galois field of two elements,
>

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