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Remove --disable-atomics, require 32 bit atomics.

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Modern versions of all relevant architectures and tool chains have
atomics support.  Since edadeb07, there is no remaining reason to carry
code that simulates atomic flags and uint32 imperfectly with spinlocks.
64 bit atomics are still emulated with spinlocks, if needed, for now.

Any modern compiler capable of implementing C11 <stdatomic.h> must have
the underlying operations we need, though we don't require C11 yet.  We
detect certain compilers and architectures, so hypothetical new systems
might need adjustments here.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> (concept, not the patch)
Reviewed-by: Andres Freund <andres@anarazel.de> (concept, not the patch)
Discussion: https://postgr.es/m/3351991.1697728588%40sss.pgh.pa.us
This commit is contained in:
Thomas Munro
2024-07-30 21:52:46 +12:00
parent e25626677f
commit 8138526136
12 changed files with 39 additions and 345 deletions
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65
meson.build
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@ -2089,70 +2089,61 @@ endif
# Atomics
###############################################################
if not get_option('atomics')
warning('Not using atomics will cause poor performance')
else
# XXX: perhaps we should require some atomics support in this case these
# days?
cdata.set('HAVE_ATOMICS', 1)
atomic_checks = [
{'name': 'HAVE_GCC__SYNC_CHAR_TAS',
'desc': '__sync_lock_test_and_set(char)',
'test': '''
atomic_checks = [
{'name': 'HAVE_GCC__SYNC_CHAR_TAS',
'desc': '__sync_lock_test_and_set(char)',
'test': '''
char lock = 0;
__sync_lock_test_and_set(&lock, 1);
__sync_lock_release(&lock);'''},
{'name': 'HAVE_GCC__SYNC_INT32_TAS',
'desc': '__sync_lock_test_and_set(int32)',
'test': '''
{'name': 'HAVE_GCC__SYNC_INT32_TAS',
'desc': '__sync_lock_test_and_set(int32)',
'test': '''
int lock = 0;
__sync_lock_test_and_set(&lock, 1);
__sync_lock_release(&lock);'''},
{'name': 'HAVE_GCC__SYNC_INT32_CAS',
'desc': '__sync_val_compare_and_swap(int32)',
'test': '''
{'name': 'HAVE_GCC__SYNC_INT32_CAS',
'desc': '__sync_val_compare_and_swap(int32)',
'test': '''
int val = 0;
__sync_val_compare_and_swap(&val, 0, 37);'''},
{'name': 'HAVE_GCC__SYNC_INT64_CAS',
'desc': '__sync_val_compare_and_swap(int64)',
'test': '''
{'name': 'HAVE_GCC__SYNC_INT64_CAS',
'desc': '__sync_val_compare_and_swap(int64)',
'test': '''
INT64 val = 0;
__sync_val_compare_and_swap(&val, 0, 37);'''},
{'name': 'HAVE_GCC__ATOMIC_INT32_CAS',
'desc': ' __atomic_compare_exchange_n(int32)',
'test': '''
{'name': 'HAVE_GCC__ATOMIC_INT32_CAS',
'desc': ' __atomic_compare_exchange_n(int32)',
'test': '''
int val = 0;
int expect = 0;
__atomic_compare_exchange_n(&val, &expect, 37, 0, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);'''},
{'name': 'HAVE_GCC__ATOMIC_INT64_CAS',
'desc': ' __atomic_compare_exchange_n(int64)',
'test': '''
{'name': 'HAVE_GCC__ATOMIC_INT64_CAS',
'desc': ' __atomic_compare_exchange_n(int64)',
'test': '''
INT64 val = 0;
INT64 expect = 0;
__atomic_compare_exchange_n(&val, &expect, 37, 0, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);'''},
]
]
foreach check : atomic_checks
test = '''
foreach check : atomic_checks
test = '''
int main(void)
{
@0@
}'''.format(check['test'])
cdata.set(check['name'],
cc.links(test,
name: check['desc'],
args: test_c_args + ['-DINT64=@0@'.format(cdata.get('PG_INT64_TYPE'))]) ? 1 : false
)
endforeach
endif
cdata.set(check['name'],
cc.links(test,
name: check['desc'],
args: test_c_args + ['-DINT64=@0@'.format(cdata.get('PG_INT64_TYPE'))]) ? 1 : false
)
endforeach
###############################################################