* [Patch] GCN: Implement __atomic_compare_exchange_{1,2} in libgcc [PR102215]
@ 2022-03-09 16:29 Tobias Burnus
2022-03-09 16:36 ` [Patch] GCN: Implement __atomic_compare_exchange_{1, 2} " Andrew Stubbs
0 siblings, 1 reply; 2+ messages in thread
From: Tobias Burnus @ 2022-03-09 16:29 UTC (permalink / raw)
To: gcc-patches, Andrew Stubbs
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This shows up with with OpenMP offloading as libgomp since a couple
of months uses __atomic_compare_exchange (see PR for details),
causing link errors when the gcn libgomp.a is linked.
It also shows up with sollve_vv.
The implementation does a bit copy'n'paste from the current
implementation + calls the existing word/uint32_t-wide version
of the atomic intrinsic. The semantic is described at
https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
In terms of the args, the _4 has:
DEF_SYNC_BUILTIN (BUILT_IN_ATOMIC_COMPARE_EXCHANGE_4,
"__atomic_compare_exchange_4",
BT_FN_BOOL_VPTR_PTR_I4_BOOL_INT_INT,
ATTR_NOTHROWCALL_LEAF_LIST)
and the arg names try to match the GCC manual.
OK for mainline?
Tested with libgomp + sollve_vv and -march=gfx908.
Tobias
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GCN: Implement __atomic_compare_exchange_{1,2} in libgcc [PR102215]
libgcc/ChangeLog:
PR target/102215
* config/gcn/atomic.c (__sync_val_compare_and_swap_##SIZE): Move
a line up to non-arg-dependent value first.
(__ATOMIC_COMPARE_EXCHANGE): Define + call to generate
__atomic_compare_exchange_{1,2}.
diff --git a/libgcc/config/gcn/atomic.c b/libgcc/config/gcn/atomic.c
index 8784f90dfe2..cf29fa82aba 100644
--- a/libgcc/config/gcn/atomic.c
+++ b/libgcc/config/gcn/atomic.c
@@ -18,42 +18,69 @@
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
#include <stdbool.h>
#define __SYNC_SUBWORD_COMPARE_AND_SWAP(TYPE, SIZE) \
\
TYPE \
__sync_val_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval) \
{ \
+ unsigned int valmask = (1 << (SIZE * 8)) - 1; \
unsigned int *wordptr = (unsigned int *)((__UINTPTR_TYPE__ ) ptr & ~3UL); \
int shift = ((__UINTPTR_TYPE__ ) ptr & 3UL) * 8; \
- unsigned int valmask = (1 << (SIZE * 8)) - 1; \
unsigned int wordmask = ~(valmask << shift); \
unsigned int oldword = *wordptr; \
for (;;) \
{ \
TYPE prevval = (oldword >> shift) & valmask; \
if (__builtin_expect (prevval != oldval, 0)) \
return prevval; \
unsigned int newword = oldword & wordmask; \
newword |= ((unsigned int) newval) << shift; \
unsigned int prevword \
= __sync_val_compare_and_swap_4 (wordptr, oldword, newword); \
if (__builtin_expect (prevword == oldword, 1)) \
return oldval; \
oldword = prevword; \
} \
} \
\
bool \
__sync_bool_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval) \
{ \
return __sync_val_compare_and_swap_##SIZE (ptr, oldval, newval) == oldval; \
}
__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned char, 1)
__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned short, 2)
+
+#define __ATOMIC_COMPARE_EXCHANGE(TYPE,SIZE) \
+bool \
+__atomic_compare_exchange_##SIZE (TYPE *ptr, TYPE *expected, \
+ TYPE desired, bool weak, \
+ int success_memorder, int failure_memorder) \
+{ \
+ unsigned int valmask = (1 << (SIZE * 8)) - 1; \
+ \
+ unsigned int *wordptr = (unsigned int *)((__UINTPTR_TYPE__ ) ptr & ~3UL); \
+ int ptrshift = ((__UINTPTR_TYPE__ ) ptr & 3UL) * 8; \
+ unsigned int wordmask = ~(valmask << ptrshift); \
+ \
+ unsigned int ptrword = *wordptr; \
+ unsigned int exptword = ptrword & wordmask; \
+ unsigned int newword = ptrword & wordmask; \
+ exptword |= ((unsigned int) *expected) << ptrshift; \
+ newword |= ((unsigned int) desired) << ptrshift; \
+ if (__atomic_compare_exchange_4 (wordptr, &exptword, newword, weak, \
+ success_memorder, failure_memorder)) \
+ return true; \
+ *expected = (TYPE) ((exptword >> ptrshift) & valmask); \
+ return false; \
+}
+
+__ATOMIC_COMPARE_EXCHANGE (unsigned char, 1)
+__ATOMIC_COMPARE_EXCHANGE (unsigned short, 2)
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Patch] GCN: Implement __atomic_compare_exchange_{1, 2} in libgcc [PR102215]
2022-03-09 16:29 [Patch] GCN: Implement __atomic_compare_exchange_{1,2} in libgcc [PR102215] Tobias Burnus
@ 2022-03-09 16:36 ` Andrew Stubbs
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Stubbs @ 2022-03-09 16:36 UTC (permalink / raw)
To: Tobias Burnus, gcc-patches
On 09/03/2022 16:29, Tobias Burnus wrote:
> This shows up with with OpenMP offloading as libgomp since a couple
> of months uses __atomic_compare_exchange (see PR for details),
> causing link errors when the gcn libgomp.a is linked.
> It also shows up with sollve_vv.
>
> The implementation does a bit copy'n'paste from the current
> implementation + calls the existing word/uint32_t-wide version
> of the atomic intrinsic. The semantic is described at
> https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
>
> In terms of the args, the _4 has:
> DEF_SYNC_BUILTIN (BUILT_IN_ATOMIC_COMPARE_EXCHANGE_4,
> "__atomic_compare_exchange_4",
> BT_FN_BOOL_VPTR_PTR_I4_BOOL_INT_INT,
> ATTR_NOTHROWCALL_LEAF_LIST)
> and the arg names try to match the GCC manual.
>
>
> OK for mainline?
> Tested with libgomp + sollve_vv and -march=gfx908.
OK.
Andrew
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2022-03-09 16:36 ` [Patch] GCN: Implement __atomic_compare_exchange_{1, 2} " Andrew Stubbs
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