[Bug target/105011] [nvptx] FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105011 Tom de Vries changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Target Milestone|--- |12.0 Resolution|--- |FIXED --- Comment #5 from Tom de Vries --- Fixed by commit.
[Bug target/105011] [nvptx] FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105011
--- Comment #4 from CVS Commits ---
The master branch has been updated by Tom de Vries :
https://gcc.gnu.org/g:11fb784ac592567dbcb7874c27e67ee0feb8fbf0
commit r12-7799-g11fb784ac592567dbcb7874c27e67ee0feb8fbf0
Author: Tom de Vries
Date: Wed Mar 23 16:37:45 2022 +0100
[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
atomic_flag a = ATOMIC_FLAG_INIT;
int main () {
if ((atomic_flag_test_and_set) ())
__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
PR target/105011
* tas_n.c (libat_test_and_set): Fix return value.
[Bug target/105011] [nvptx] FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105011 --- Comment #3 from Tom de Vries --- Submitted fix : https://gcc.gnu.org/pipermail/gcc-patches/2022-March/592211.html Though without changelog, apparently.
[Bug target/105011] [nvptx] FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105011 --- Comment #2 from Tom de Vries --- Even better: ... diff --git a/libatomic/tas_n.c b/libatomic/tas_n.c index d0d8c283b495..65eaa7753a51 100644 --- a/libatomic/tas_n.c +++ b/libatomic/tas_n.c @@ -73,7 +73,7 @@ SIZE(libat_test_and_set) (UTYPE *mptr, int smodel) __ATOMIC_RELAXED, __ATOMIC_RELAXED)); post_barrier (smodel); - return woldval != 0; + return (woldval & wval) == wval; } #define DONE 1 ... That also gives back accurate results in case TARGET_ATOMIC_TEST_AND_SET_TRUEVAL has more than one bit set.
[Bug target/105011] [nvptx] FAIL: gcc.dg/atomic/stdatomic-flag-2.c -O1 execution test
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105011 --- Comment #1 from Tom de Vries --- (In reply to Tom de Vries from comment #0) > It should probably do something like: > ... > return (woldval & wval) != 0; > ... Indeed, that fixes the FAILs.
