Hi Jakub,
On 10.02.20 08:49, Harwath, Frederik wrote:
>> There has been even in some PR a suggestion that instead of failing
>> in nvptx async_run we should just ignore the nowait clause if the plugin
>> doesn't implement it properly.
>
> This must be https://gcc.gnu.org/PR93481.
The attached patch implements the behavior that has been suggested in the PR.
It makes GOMP_OFFLOAD_async_run optional, removes the stub which produces
the error described in the PR from the nvptx plugin, and changes the
nowait-handling
to ignore the clause if GOMP_OFFLOAD_async_run is not available for the
executing
device's plugin. I have tested the patch by running the full libgomp testsuite
with
nvptx-none offloading on x86_64-linux-gnu. I have observed no regressions.
Ok to push the commit to master?
For the record: Someone should implement GOMP_OFFLOAD_async_run properly
in the nvtpx plugin.
Best regards,
Frederik
From 1258f713be317870e9171281e3f7c3a174773aa1 Mon Sep 17 00:00:00 2001
From: Frederik Harwath <frede...@codesourcery.com>
Date: Thu, 13 Feb 2020 07:30:16 +0100
Subject: [PATCH] openmp: ignore nowait if async execution is unsupported
[PR93481]
An OpenMP "nowait" clause on a target construct currently leads to
a call to GOMP_OFFLOAD_async_run in the plugin that is used for
offloading at execution time. The nvptx plugin contains only a stub
of this function that always produces a fatal error if called.
This commit changes the "nowait" implementation to ignore the clause
if the executing device's plugin does not implement GOMP_OFFLOAD_async_run.
The stub in the nvptx plugin is removed which effectively means that
programs containing "nowait" can now be executed with nvptx offloading
as if the clause had not been used.
This behavior is consistent with the OpenMP specification which says that
"[...] execution of the target task *may* be deferred" (emphasis added),
cf. OpenMP 5.0, page 172.
libgomp/
* plugin/plugin-nvptx.c: Remove GOMP_OFFLOAD_async_run stub.
* target.c (gomp_load_plugin_for_device): Make "async_run" loading
optional.
(gomp_target_task_fn): Assert "devicep->async_run_func".
(clear_unsupported_flags): New function to remove unsupported flags
(right now only GOMP_TARGET_FLAG_NOWAIT) that can be be ignored.
(GOMP_target_ext): Apply clear_unsupported_flags to flags.
(GOMP_target_update_ext): Likewise.
(GOMP_target_enter_exit_data): Likewise.
* testsuite/libgomp.c/target-33.c:
Remove xfail for offload_target_nvptx.
* testsuite/libgomp.c/target-34.c: Likewise.
---
libgomp/plugin/plugin-nvptx.c | 7 +------
libgomp/target.c | 19 ++++++++++++++++++-
libgomp/testsuite/libgomp.c/target-33.c | 3 ---
libgomp/testsuite/libgomp.c/target-34.c | 3 ---
4 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/libgomp/plugin/plugin-nvptx.c b/libgomp/plugin/plugin-nvptx.c
index 6033c71a9db..ec103a2f40b 100644
--- a/libgomp/plugin/plugin-nvptx.c
+++ b/libgomp/plugin/plugin-nvptx.c
@@ -1931,9 +1931,4 @@ GOMP_OFFLOAD_run (int ord, void *tgt_fn, void *tgt_vars, void **args)
nvptx_stacks_free (stacks, teams * threads);
}
-void
-GOMP_OFFLOAD_async_run (int ord, void *tgt_fn, void *tgt_vars, void **args,
- void *async_data)
-{
- GOMP_PLUGIN_fatal ("GOMP_OFFLOAD_async_run unimplemented");
-}
+/* TODO: Implement GOMP_OFFLOAD_async_run. */
diff --git a/libgomp/target.c b/libgomp/target.c
index 3df007283f4..4fbf963f305 100644
--- a/libgomp/target.c
+++ b/libgomp/target.c
@@ -2022,6 +2022,16 @@ GOMP_target (int device, void (*fn) (void *), const void *unused,
gomp_unmap_vars (tgt_vars, true);
}
+static unsigned int
+clear_unsupported_flags (struct gomp_device_descr *devicep, unsigned int flags)
+{
+ /* If we cannot run asynchronously, simply ignore nowait. */
+ if (devicep != NULL && devicep->async_run_func == NULL)
+ flags &= ~GOMP_TARGET_FLAG_NOWAIT;
+
+ return flags;
+}
+
/* Like GOMP_target, but KINDS is 16-bit, UNUSED is no longer present,
and several arguments have been added:
FLAGS is a bitmask, see GOMP_TARGET_FLAG_* in gomp-constants.h.
@@ -2054,6 +2064,8 @@ GOMP_target_ext (int device, void (*fn) (void *), size_t mapnum,
size_t tgt_align = 0, tgt_size = 0;
bool fpc_done = false;
+ flags = clear_unsupported_flags (devicep, flags);
+
if (flags & GOMP_TARGET_FLAG_NOWAIT)
{
struct gomp_thread *thr = gomp_thread ();
@@ -2257,6 +2269,8 @@ GOMP_target_update_ext (int device, size_t mapnum, void **hostaddrs,
{
struct gomp_device_descr *devicep = resolve_device (device);
+ flags = clear_unsupported_flags (devicep, flags);
+
/* If there are depend clauses, but nowait is not present,
block the parent task until the dependencies are resolved
and then just continue with the rest of the function as if it
@@ -2398,6 +2412,8 @@ GOMP_target_enter_exit_data (int device, size_t mapnum, void **hostaddrs,
{
struct gomp_device_descr *devicep = resolve_device (device);
+ flags = clear_unsupported_flags (devicep, flags);
+
/* If there are depend clauses, but nowait is not present,
block the parent task until the dependencies are resolved
and then just continue with the rest of the function as if it
@@ -2524,6 +2540,7 @@ gomp_target_task_fn (void *data)
}
ttask->state = GOMP_TARGET_TASK_READY_TO_RUN;
+ assert (devicep->async_run_func);
devicep->async_run_func (devicep->target_id, fn_addr, actual_arguments,
ttask->args, (void *) ttask);
return true;
@@ -3040,7 +3057,7 @@ gomp_load_plugin_for_device (struct gomp_device_descr *device,
if (device->capabilities & GOMP_OFFLOAD_CAP_OPENMP_400)
{
DLSYM (run);
- DLSYM (async_run);
+ DLSYM_OPT (async_run, async_run);
DLSYM_OPT (can_run, can_run);
DLSYM (dev2dev);
}
diff --git a/libgomp/testsuite/libgomp.c/target-33.c b/libgomp/testsuite/libgomp.c/target-33.c
index 15d2d7e38ab..1bed4b6bc67 100644
--- a/libgomp/testsuite/libgomp.c/target-33.c
+++ b/libgomp/testsuite/libgomp.c/target-33.c
@@ -1,6 +1,3 @@
-/* { dg-xfail-run-if "GOMP_OFFLOAD_async_run not implemented" { offload_target_nvptx } }
- Cf. https://gcc.gnu.org/PR81688. */
-
extern void abort (void);
int
diff --git a/libgomp/testsuite/libgomp.c/target-34.c b/libgomp/testsuite/libgomp.c/target-34.c
index 5a3596424d8..66d9f54202b 100644
--- a/libgomp/testsuite/libgomp.c/target-34.c
+++ b/libgomp/testsuite/libgomp.c/target-34.c
@@ -1,6 +1,3 @@
-/* { dg-xfail-run-if "GOMP_OFFLOAD_async_run not implemented" { offload_target_nvptx } }
- Cf. https://gcc.gnu.org/PR81688. */
-
extern void abort (void);
int
--
2.17.1
