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Extend configure's __int128 test to check for a known gcc bug. 

On Sparc64, use of __attribute__(aligned(8)) with __int128 causes faulty
code generation in gcc versions at least through 5.5.0.  We can work around
that by disabling use of __int128, so teach configure to test for the bug.

This solution doesn't fix things for the case of cross-compiling with a
buggy compiler; to support that nicely, we'd need to add a manual disable
switch.  Unless more such cases turn up, it doesn't seem worth the work.
Affected users could always edit pg_config.h manually.

In passing, fix some typos in the existing configure test for __int128.
They're harmless because we only compile that code not run it, but
they're still confusing for anyone looking at it closely.

This is needed in support of commit 751804998, so back-patch to 9.5
as that was.

Marina Polyakova, Victor Wagner, Tom Lane

Discussion: https://postgr.es/m/0d3a9fa264cebe1cb9966f37b7c06e86@postgrespro.ru
This commit is contained in:
Tom Lane 2018-01-18 11:09:44 -05:00
parent a063d842f8
commit 2082b3745a
2 changed files with 105 additions and 15 deletions
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48
config/c-compiler.m4
View File

@ -108,29 +108,61 @@ AC_DEFUN([PGAC_TYPE_128BIT_INT],
[AC_CACHE_CHECK([for __int128], [pgac_cv__128bit_int],
[AC_LINK_IFELSE([AC_LANG_PROGRAM([
/*
* We don't actually run this test, just link it to verify that any support
* functions needed for __int128 are present.
*
* 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...
* convenient support for 128bit literals at this point...
*/
__int128 a = 48828125;
__int128 b = 97656255;
__int128 b = 97656250;
],[
__int128 c,d;
a = (a << 12) + 1; /* 200000000001 */
b = (b << 12) + 5; /* 400000000005 */
/* use the most relevant arithmetic ops */
/* try the most relevant arithmetic ops */
c = a * b;
d = (c + b) / b;
/* return different values, to prevent optimizations */
/* must use the results, else compiler may optimize arithmetic away */
if (d != a+1)
return 0;
return 1;
return 1;
])],
[pgac_cv__128bit_int=yes],
[pgac_cv__128bit_int=no])])
if test x"$pgac_cv__128bit_int" = xyes ; then
AC_DEFINE(PG_INT128_TYPE, __int128, [Define to the name of a signed 128-bit integer type.])
AC_CHECK_ALIGNOF(PG_INT128_TYPE)
# Use of non-default alignment with __int128 tickles bugs in some compilers.
# If not cross-compiling, we can test for bugs and disable use of __int128
# with buggy compilers. If cross-compiling, hope for the best.
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83925
AC_CACHE_CHECK([for __int128 alignment bug], [pgac_cv__128bit_int_bug],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([
/* This must match the corresponding code in c.h: */
#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
#define pg_attribute_aligned(a) __attribute__((aligned(a)))
#endif
typedef __int128 int128a
#if defined(pg_attribute_aligned)
pg_attribute_aligned(8)
#endif
;
int128a holder;
void pass_by_val(void *buffer, int128a par) { holder = par; }
],[
long int i64 = 97656225L << 12;
int128a q;
pass_by_val(main, (int128a) i64);
q = (int128a) i64;
if (q != holder)
return 1;
])],
[pgac_cv__128bit_int_bug=ok],
[pgac_cv__128bit_int_bug=broken],
[pgac_cv__128bit_int_bug="assuming ok"])])
if test x"$pgac_cv__128bit_int_bug" != xbroken ; then
AC_DEFINE(PG_INT128_TYPE, __int128, [Define to the name of a signed 128-bit integer type.])
AC_CHECK_ALIGNOF(PG_INT128_TYPE)
fi
fi])# PGAC_TYPE_128BIT_INT

72
configure vendored
View File

@ -14996,12 +14996,15 @@ else
/* end confdefs.h. */
/*
* We don't actually run this test, just link it to verify that any support
* functions needed for __int128 are present.
*
* 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...
* convenient support for 128bit literals at this point...
*/
__int128 a = 48828125;
__int128 b = 97656255;
__int128 b = 97656250;
int
main ()
@ -15010,13 +15013,12 @@ main ()
__int128 c,d;
a = (a << 12) + 1; /* 200000000001 */
b = (b << 12) + 5; /* 400000000005 */
/* use the most relevant arithmetic ops */
/* try the most relevant arithmetic ops */
c = a * b;
d = (c + b) / b;
/* return different values, to prevent optimizations */
/* must use the results, else compiler may optimize arithmetic away */
if (d != a+1)
return 0;
return 1;
return 1;
;
return 0;
@ -15033,10 +15035,65 @@ 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
# Use of non-default alignment with __int128 tickles bugs in some compilers.
# If not cross-compiling, we can test for bugs and disable use of __int128
# with buggy compilers. If cross-compiling, hope for the best.
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83925
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __int128 alignment bug" >&5
$as_echo_n "checking for __int128 alignment bug... " >&6; }
if ${pgac_cv__128bit_int_bug+:} false; then :
$as_echo_n "(cached) " >&6
else
if test "$cross_compiling" = yes; then :
pgac_cv__128bit_int_bug="assuming ok"
else
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
/* This must match the corresponding code in c.h: */
#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
#define pg_attribute_aligned(a) __attribute__((aligned(a)))
#endif
typedef __int128 int128a
#if defined(pg_attribute_aligned)
pg_attribute_aligned(8)
#endif
;
int128a holder;
void pass_by_val(void *buffer, int128a par) { holder = par; }
int
main ()
{
long int i64 = 97656225L << 12;
int128a q;
pass_by_val(main, (int128a) i64);
q = (int128a) i64;
if (q != holder)
return 1;
;
return 0;
}
_ACEOF
if ac_fn_c_try_run "$LINENO"; then :
pgac_cv__128bit_int_bug=ok
else
pgac_cv__128bit_int_bug=broken
fi
rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
conftest.$ac_objext conftest.beam conftest.$ac_ext
fi
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__128bit_int_bug" >&5
$as_echo "$pgac_cv__128bit_int_bug" >&6; }
if test x"$pgac_cv__128bit_int_bug" != xbroken ; then
$as_echo "#define PG_INT128_TYPE __int128" >>confdefs.h
# The cast to long int works around a bug in the HP C Compiler,
# The cast to long int works around a bug in the HP C Compiler,
# see AC_CHECK_SIZEOF for more information.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking alignment of PG_INT128_TYPE" >&5
$as_echo_n "checking alignment of PG_INT128_TYPE... " >&6; }
@ -15071,6 +15128,7 @@ cat >>confdefs.h <<_ACEOF
_ACEOF
fi
fi
# Check for various atomic operations now that we have checked how to declare