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authorTom de Vries <tdevries@suse.de>2022-03-23 16:37:45 +0100
committerTom de Vries <tdevries@suse.de>2022-03-24 13:30:57 +0100
commit11fb784ac592567dbcb7874c27e67ee0feb8fbf0 (patch)
treefc2e87f8bad1ff57287669a7b1406b8cdad7c10d /libatomic
parenttestsuite: Add compat.exp testcase for most common zero width bitfld ABI pass... (diff)
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[libatomic] Fix return value in libat_test_and_set
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.
Diffstat (limited to 'libatomic')
-rw-r--r--libatomic/tas_n.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/libatomic/tas_n.c b/libatomic/tas_n.c
index d0d8c283b49..524312e7d8d 100644
--- a/libatomic/tas_n.c
+++ b/libatomic/tas_n.c
@@ -73,7 +73,7 @@ SIZE(libat_test_and_set) (UTYPE *mptr, int smodel)
73 __ATOMIC_RELAXED, __ATOMIC_RELAXED)); 73 __ATOMIC_RELAXED, __ATOMIC_RELAXED));
74 74
75 post_barrier (smodel); 75 post_barrier (smodel);
76 return woldval != 0; 76 return (woldval & ((UTYPE) ~(UTYPE) 0 << shift)) != 0;
77} 77}
78 78
79#define DONE 1 79#define DONE 1