Re: tweaking MemSet() performance - 7.4.5 - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: tweaking MemSet() performance - 7.4.5
Date
Msg-id 200409300147.i8U1l6209508@candle.pha.pa.us
Whole thread Raw
In response to Re: tweaking MemSet() performance - 7.4.5  (Neil Conway <neilc@samurai.com>)
Responses Re: tweaking MemSet() performance - 7.4.5  (Peter Eisentraut <peter_e@gmx.net>)
List pgsql-hackers
Neil Conway wrote:
> On Wed, 2004-09-29 at 21:37, Bruce Momjian wrote:
> > The reason MemSet is a win is not that the C code is great but because
> > it eliminates a function call.
> 
> A reasonable compiler ought to be able to implement memset() as a
> compiler intrinsic where it makes sense to do so. MSVC++ can certainly
> do this; per the GCC 3.4 docs, it seems GCC can/does as well:
> 
> The ISO C90 functions abort, abs, acos, asin, atan2, atan, calloc, ceil,
> cosh, cos, exit, exp, fabs, floor, fmod, fprintf, fputs, frexp, fscanf,
> labs, ldexp, log10, log, malloc, memcmp, memcpy, memset, modf, pow,
> printf, putchar, puts, scanf, sinh, sin, snprintf, sprintf, sqrt,
> sscanf, strcat, strchr, strcmp, strcpy, strcspn, strlen, strncat,
> strncmp, strncpy, strpbrk, strrchr, strspn, strstr, tanh, tan, vfprintf,
> vprintf and vsprintf are all recognized as built-in functions unless
> -fno-builtin is specified (or -fno-builtin-function is specified for an
> individual function). All of these functions have corresponding versions
> prefixed with __builtin_.
> 
> (http://gcc.gnu.org/onlinedocs/gcc-3.4.2/gcc/Other-Builtins.html#Other-Builtins)

MemSet was written when gcc 2.X wasn't even stable yet.  Have you run
any tests on 3.4 to see if MemSet is still a win with that compiler?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
359-1001+  If your life is a hard drive,     |  13 Roberts Road +  Christ can be your backup.        |  Newtown Square,
Pennsylvania19073
 


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