In order to facilitate the fine-tuning of how `libatomic_i.h' and
`host-config.h' headers are used by different atomic functions, we
define distinct identifier macros for each file which, in implementing
atomic operations, imports these headers.
The idea is that different parts of these headers could then be
conditionally defined depending on the macros set by the file that
`#include'd them.
Given how it is possible that some file names are generic enough that
using them as-is for macro names (e.g. flag.c -> FLAG) may potentially
lead to name clashes with other macros, all file names first have LAT_
prepended to them such that, for example, flag.c is assigned the
LAT_FLAG macro.
Libatomic/ChangeLog:
* cas_n.c (LAT_CAS_N): New.
* exch_n.c (LAT_EXCH_N): Likewise.
* fadd_n.c (LAT_FADD_N): Likewise.
* fand_n.c (LAT_FAND_N): Likewise.
* fence.c (LAT_FENCE): Likewise.
* fenv.c (LAT_FENV): Likewise.
* fior_n.c (LAT_FIOR_N): Likewise.
* flag.c (LAT_FLAG): Likewise.
* fnand_n.c (LAT_FNAND_N): Likewise.
* fop_n.c (LAT_FOP_N): Likewise
* fsub_n.c (LAT_FSUB_N): Likewise.
* fxor_n.c (LAT_FXOR_N): Likewise.
* gcas.c (LAT_GCAS): Likewise.
* gexch.c (LAT_GEXCH): Likewise.
* glfree.c (LAT_GLFREE): Likewise.
* gload.c (LAT_GLOAD): Likewise.
* gstore.c (LAT_GSTORE): Likewise.
* load_n.c (LAT_LOAD_N): Likewise.
* store_n.c (LAT_STORE_N): Likewise.
* tas_n.c (LAT_TAS_N): Likewise.
On nvptx (using a Quadro K2000 with driver 470.103.01) I ran into this:
...
FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
...
which mimimized to:
...
#include <stdatomic.h>
atomic_flag a = ATOMIC_FLAG_INIT;
int main () {
if ((atomic_flag_test_and_set) (&a))
__builtin_abort ();
return 0;
}
...
The atomic_flag_test_and_set is implemented using __atomic_test_and_set_1,
which corresponds to the "word-sized compare-and-swap loop" version of
libat_test_and_set in libatomic/tas_n.c.
The semantics of a test-and-set is that the return value is "true if and only
if the previous contents were 'set'".
But the code uses:
...
return woldval != 0;
...
which means it doesn't look only at the byte that was either set or not set,
but at the entire word.
Fix this by using instead:
...
return (woldval & ((UTYPE) ~(UTYPE) 0 << shift)) != 0;
...
Tested on nvptx.
libatomic/ChangeLog:
2022-03-24 Tom de Vries <tdevries@suse.de>
PR target/105011
* tas_n.c (libat_test_and_set): Fix return value.
Jakub Jelinek