libgomp, nvptx, v2: Honor OpenMP 5.1 num_teams lower bound
Commit Message
On Fri, Nov 12, 2021 at 02:20:23PM +0100, Jakub Jelinek via Gcc-patches wrote:
> This patch assumes that .shared variables are initialized to 0,
> https://docs.nvidia.com/cuda/parallel-thread-execution/index.html lists
> in Table 7. .shared as non-initializable. If that isn't the case,
> we need to initialize it somewhere for the case of #pragma omp target
> without #pragma omp teams in it, maybe in libgcc/config/nvptx/crt0.c ?
A quick look at libgcc/config/nvptx/crt0.c shows the target supports
__attribute__((shared)), so perhaps either following instead, or, if
.shared isn't preinitialized to zero, defining the variable in
libgcc/config/nvptx/crt0.c , adding there __gomp_team_num = 0;
and adding extern keyword before int __gomp_team_num __attribute__((shared));
in libgomp/config/nvptx/target.c.
2021-11-12 Jakub Jelinek <jakub@redhat.com>
* config/nvptx/target.c (__gomp_team_num): Define as
__attribute__((shared)) var.
(GOMP_teams4): Use __gomp_team_num as the team number instead of
%ctaid.x. If first, initialize it to %ctaid.x. If num_teams_lower
is bigger than num_blocks, use num_teams_lower teams and arrange for
bumping of __gomp_team_num if !first and returning false once we run
out of teams.
* config/nvptx/teams.c (__gomp_team_num): Declare as
extern __attribute__((shared)) var.
(omp_get_team_num): Return __gomp_team_num value instead of %ctaid.x.
Jakub
@@ -26,28 +26,41 @@
#include "libgomp.h"
#include <limits.h>
+int __gomp_team_num __attribute__((shared));
+
bool
GOMP_teams4 (unsigned int num_teams_lower, unsigned int num_teams_upper,
unsigned int thread_limit, bool first)
{
+ unsigned int num_blocks, block_id;
+ asm ("mov.u32 %0, %%nctaid.x;" : "=r" (num_blocks));
if (!first)
- return false;
+ {
+ unsigned in team_num;
+ if (num_blocks > gomp_num_teams_var)
+ return false;
+ team_num = __gomp_team_num;
+ if (team_num > gomp_num_teams_var - num_blocks)
+ return false;
+ __gomp_team_num = team_num + num_blocks;
+ return true;
+ }
if (thread_limit)
{
struct gomp_task_icv *icv = gomp_icv (true);
icv->thread_limit_var
= thread_limit > INT_MAX ? UINT_MAX : thread_limit;
}
- unsigned int num_blocks, block_id;
- asm ("mov.u32 %0, %%nctaid.x;" : "=r" (num_blocks));
- asm ("mov.u32 %0, %%ctaid.x;" : "=r" (block_id));
- /* FIXME: If num_teams_lower > num_blocks, we want to loop multiple
- times for some CTAs. */
- (void) num_teams_lower;
- if (!num_teams_upper || num_teams_upper >= num_blocks)
+ if (!num_teams_upper)
num_teams_upper = num_blocks;
- else if (block_id >= num_teams_upper)
+ else if (num_blocks < num_teams_lower)
+ num_teams_upper = num_teams_lower;
+ else if (num_blocks < num_teams_upper)
+ num_teams_upper = num_blocks;
+ asm ("mov.u32 %0, %%ctaid.x;" : "=r" (block_id));
+ if (block_id >= num_teams_upper)
return false;
+ __gomp_team_num = block_id;
gomp_num_teams_var = num_teams_upper - 1;
return true;
}
@@ -28,6 +28,8 @@
#include "libgomp.h"
+extern int __gomp_team_num __attribute__((shared));
+
void
GOMP_teams_reg (void (*fn) (void *), void *data, unsigned int num_teams,
unsigned int thread_limit, unsigned int flags)
@@ -48,9 +50,7 @@ omp_get_num_teams (void)
int
omp_get_team_num (void)
{
- int ctaid;
- asm ("mov.u32 %0, %%ctaid.x;" : "=r" (ctaid));
- return ctaid;
+ return __gomp_team_num;
}
ialias (omp_get_num_teams)