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Add, optional, support for 128bit integers.

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We will, for the foreseeable future, not expose 128 bit datatypes to
SQL. But being able to use 128bit math will allow us, in a later patch,
to use 128bit accumulators for some aggregates; leading to noticeable
speedups over using numeric.

So far we only detect a gcc/clang extension that supports 128bit math,
but no 128bit literals, and no *printf support. We might want to expand
this in the future to further compilers; if there are any that that
provide similar support.

Discussion: 544BB5F1.50709@proxel.se
Author: Andreas Karlsson, with significant editorializing by me
Reviewed-By: Peter Geoghegan, Oskari Saarenmaa
This commit is contained in:
Andres Freund
2015-03-20 10:26:17 +01:00
parent 7e9ed623d9
commit 8122e1437e
6 changed files with 109 additions and 0 deletions
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52
configure vendored
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@ -13803,6 +13803,58 @@ _ACEOF
fi
# Check for extensions offering the integer scalar type __int128.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __int128" >&5
$as_echo_n "checking for __int128... " >&6; }
if ${pgac_cv__128bit_int+:} false; then :
$as_echo_n "(cached) " >&6
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
/*
* These are globals to discourage the compiler from folding all the
* arithmetic tests down to compile-time constants. We do not have
* convenient support for 64bit literals at this point...
*/
__int128 a = 48828125;
__int128 b = 97656255;
int
main ()
{
__int128 c,d;
a = (a << 12) + 1; /* 200000000001 */
b = (b << 12) + 5; /* 400000000005 */
/* use the most relevant arithmetic ops */
c = a * b;
d = (c + b) / b;
/* return different values, to prevent optimizations */
if (d != a+1)
return 0;
return 1;
;
return 0;
}
_ACEOF
if ac_fn_c_try_link "$LINENO"; then :
pgac_cv__128bit_int=yes
else
pgac_cv__128bit_int=no
fi
rm -f core conftest.err conftest.$ac_objext \
conftest$ac_exeext conftest.$ac_ext
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__128bit_int" >&5
$as_echo "$pgac_cv__128bit_int" >&6; }
if test x"$pgac_cv__128bit_int" = xyes ; then
$as_echo "#define PG_INT128_TYPE __int128" >>confdefs.h
fi
# Check for various atomic operations now that we have checked how to declare
# 64bit integers.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for builtin __sync char locking functions" >&5