[gcc r14-9629] openmp: Change to using a hashtab to lookup offload target addresses for indirect function calls
Kwok Yeung
kcy@gcc.gnu.org
Fri Mar 22 18:10:54 GMT 2024
https://gcc.gnu.org/g:637e76b90e8b045c5e25206a41e3be55deace8d5
commit r14-9629-g637e76b90e8b045c5e25206a41e3be55deace8d5
Author: Kwok Cheung Yeung <kcyeung@baylibre.com>
Date: Fri Mar 22 18:07:43 2024 +0000
openmp: Change to using a hashtab to lookup offload target addresses for indirect function calls
A splay-tree was previously used to lookup equivalent target addresses
for a given host address on offload targets. However, as splay-trees can
modify their structure on lookup, they are not suitable for concurrent
access from separate teams/threads without some form of locking. This
patch changes the lookup data structure to a hashtab instead, which does
not have these issues.
The call to build_indirect_map to initialize the data structure is now
called from just the first thread of the first team to avoid redundant
calls to this function.
2024-03-22 Kwok Cheung Yeung <kcyeung@baylibre.com>
libgomp/
* config/accel/target-indirect.c: Include string.h and hashtab.h.
Remove include of splay-tree.h. Update comments.
(splay_tree_prefix, splay_tree_c): Delete.
(struct indirect_map_t): New.
(hash_entry_type, htab_alloc, htab_free, htab_hash, htab_eq): New.
(GOMP_INDIRECT_ADD_MAP): Remove volatile qualifier.
(USE_SPLAY_TREE_LOOKUP): Rename to...
(USE_HASHTAB_LOOKUP): ..this.
(indirect_map, indirect_array): Delete.
(indirect_htab): New.
(build_indirect_map): Remove locking. Build indirect map using
hashtab.
(GOMP_target_map_indirect_ptr): Use indirect_htab to lookup target
address.
(GOMP_target_map_indirect_ptr): Remove volatile qualifier.
* config/gcn/team.c (gomp_gcn_enter_kernel): Call build_indirect_map
from first thread of first team only.
* config/nvptx/team.c (gomp_nvptx_main): Likewise.
* testsuite/libgomp.c-c++-common/declare-target-indirect-2.c (main):
Add missing break statements.
* testsuite/libgomp.fortran/declare-target-indirect-2.f90: Remove
xfail.
Diff:
---
libgomp/config/accel/target-indirect.c | 83 ++++++++++++----------
libgomp/config/gcn/team.c | 7 +-
libgomp/config/nvptx/team.c | 9 ++-
.../declare-target-indirect-2.c | 14 ++--
.../libgomp.fortran/declare-target-indirect-2.f90 | 1 -
5 files changed, 63 insertions(+), 51 deletions(-)
diff --git a/libgomp/config/accel/target-indirect.c b/libgomp/config/accel/target-indirect.c
index c60fd547cb6..cfef1ddbc49 100644
--- a/libgomp/config/accel/target-indirect.c
+++ b/libgomp/config/accel/target-indirect.c
@@ -25,60 +25,73 @@
<http://www.gnu.org/licenses/>. */
#include <assert.h>
+#include <string.h>
#include "libgomp.h"
-#define splay_tree_prefix indirect
-#define splay_tree_c
-#include "splay-tree.h"
+struct indirect_map_t
+{
+ void *host_addr;
+ void *target_addr;
+};
+
+typedef struct indirect_map_t *hash_entry_type;
+
+static inline void * htab_alloc (size_t size) { return gomp_malloc (size); }
+static inline void htab_free (void *ptr) { free (ptr); }
+
+#include "hashtab.h"
+
+static inline hashval_t
+htab_hash (hash_entry_type element)
+{
+ return hash_pointer (element->host_addr);
+}
-volatile void **GOMP_INDIRECT_ADDR_MAP = NULL;
+static inline bool
+htab_eq (hash_entry_type x, hash_entry_type y)
+{
+ return x->host_addr == y->host_addr;
+}
-/* Use a splay tree to lookup the target address instead of using a
- linear search. */
-#define USE_SPLAY_TREE_LOOKUP
+void **GOMP_INDIRECT_ADDR_MAP = NULL;
-#ifdef USE_SPLAY_TREE_LOOKUP
+/* Use a hashtab to lookup the target address instead of using a linear
+ search. */
+#define USE_HASHTAB_LOOKUP
-static struct indirect_splay_tree_s indirect_map;
-static indirect_splay_tree_node indirect_array = NULL;
+#ifdef USE_HASHTAB_LOOKUP
-/* Build the splay tree used for host->target address lookups. */
+static htab_t indirect_htab = NULL;
+
+/* Build the hashtab used for host->target address lookups. */
void
build_indirect_map (void)
{
size_t num_ind_funcs = 0;
- volatile void **map_entry;
- static int lock = 0; /* == gomp_mutex_t lock; gomp_mutex_init (&lock); */
+ void **map_entry;
if (!GOMP_INDIRECT_ADDR_MAP)
return;
- gomp_mutex_lock (&lock);
-
- if (!indirect_array)
+ if (!indirect_htab)
{
/* Count the number of entries in the NULL-terminated address map. */
for (map_entry = GOMP_INDIRECT_ADDR_MAP; *map_entry;
map_entry += 2, num_ind_funcs++);
- /* Build splay tree for address lookup. */
- indirect_array = gomp_malloc (num_ind_funcs * sizeof (*indirect_array));
- indirect_splay_tree_node array = indirect_array;
+ /* Build hashtab for address lookup. */
+ indirect_htab = htab_create (num_ind_funcs);
map_entry = GOMP_INDIRECT_ADDR_MAP;
- for (int i = 0; i < num_ind_funcs; i++, array++)
+ for (int i = 0; i < num_ind_funcs; i++, map_entry += 2)
{
- indirect_splay_tree_key k = &array->key;
- k->host_addr = (uint64_t) *map_entry++;
- k->target_addr = (uint64_t) *map_entry++;
- array->left = NULL;
- array->right = NULL;
- indirect_splay_tree_insert (&indirect_map, array);
+ struct indirect_map_t element = { *map_entry, NULL };
+ hash_entry_type *slot = htab_find_slot (&indirect_htab, &element,
+ INSERT);
+ *slot = (hash_entry_type) map_entry;
}
}
-
- gomp_mutex_unlock (&lock);
}
void *
@@ -88,15 +101,11 @@ GOMP_target_map_indirect_ptr (void *ptr)
if (!ptr)
return ptr;
- assert (indirect_array);
-
- struct indirect_splay_tree_key_s k;
- indirect_splay_tree_key node = NULL;
-
- k.host_addr = (uint64_t) ptr;
- node = indirect_splay_tree_lookup (&indirect_map, &k);
+ assert (indirect_htab);
- return node ? (void *) node->target_addr : ptr;
+ struct indirect_map_t element = { ptr, NULL };
+ hash_entry_type entry = htab_find (indirect_htab, &element);
+ return entry ? entry->target_addr : ptr;
}
#else
@@ -115,7 +124,7 @@ GOMP_target_map_indirect_ptr (void *ptr)
assert (GOMP_INDIRECT_ADDR_MAP);
- for (volatile void **map_entry = GOMP_INDIRECT_ADDR_MAP; *map_entry;
+ for (void **map_entry = GOMP_INDIRECT_ADDR_MAP; *map_entry;
map_entry += 2)
if (*map_entry == ptr)
return (void *) *(map_entry + 1);
diff --git a/libgomp/config/gcn/team.c b/libgomp/config/gcn/team.c
index 61e9c616b67..bd3df448b52 100644
--- a/libgomp/config/gcn/team.c
+++ b/libgomp/config/gcn/team.c
@@ -52,14 +52,15 @@ gomp_gcn_enter_kernel (void)
{
int threadid = __builtin_gcn_dim_pos (1);
- /* Initialize indirect function support. */
- build_indirect_map ();
-
if (threadid == 0)
{
int numthreads = __builtin_gcn_dim_size (1);
int teamid = __builtin_gcn_dim_pos(0);
+ /* Initialize indirect function support. */
+ if (teamid == 0)
+ build_indirect_map ();
+
/* Set up the global state.
Every team will do this, but that should be harmless. */
gomp_global_icv.nthreads_var = 16;
diff --git a/libgomp/config/nvptx/team.c b/libgomp/config/nvptx/team.c
index 0cf5dad39ca..d5361917a24 100644
--- a/libgomp/config/nvptx/team.c
+++ b/libgomp/config/nvptx/team.c
@@ -60,9 +60,6 @@ gomp_nvptx_main (void (*fn) (void *), void *fn_data)
asm ("mov.u32 %0, %%tid.y;" : "=r" (tid));
asm ("mov.u32 %0, %%ntid.y;" : "=r" (ntids));
- /* Initialize indirect function support. */
- build_indirect_map ();
-
if (tid == 0)
{
gomp_global_icv.nthreads_var = ntids;
@@ -74,6 +71,12 @@ gomp_nvptx_main (void (*fn) (void *), void *fn_data)
nvptx_thrs = alloca (ntids * sizeof (*nvptx_thrs));
memset (nvptx_thrs, 0, ntids * sizeof (*nvptx_thrs));
+ /* Initialize indirect function support. */
+ unsigned int block_id;
+ asm ("mov.u32 %0, %%ctaid.x;" : "=r" (block_id));
+ if (block_id == 0)
+ build_indirect_map ();
+
/* Find the low-latency heap details .... */
uint32_t *shared_pool;
uint32_t shared_pool_size = 0;
diff --git a/libgomp/testsuite/libgomp.c-c++-common/declare-target-indirect-2.c b/libgomp/testsuite/libgomp.c-c++-common/declare-target-indirect-2.c
index 9fe190efce8..545f1a9fcbf 100644
--- a/libgomp/testsuite/libgomp.c-c++-common/declare-target-indirect-2.c
+++ b/libgomp/testsuite/libgomp.c-c++-common/declare-target-indirect-2.c
@@ -17,17 +17,17 @@ int main (void)
{
switch (i % 3)
{
- case 0: fn_ptr[i] = &foo;
- case 1: fn_ptr[i] = &bar;
- case 2: fn_ptr[i] = &baz;
+ case 0: fn_ptr[i] = &foo; break;
+ case 1: fn_ptr[i] = &bar; break;
+ case 2: fn_ptr[i] = &baz; break;
}
expected += (*fn_ptr[i]) ();
}
-#pragma omp target teams distribute parallel for reduction(+: x) \
- map (to: fn_ptr) map (tofrom: x)
- for (int i = 0; i < N; i++)
- x += (*fn_ptr[i]) ();
+ #pragma omp target teams distribute parallel for \
+ reduction (+: x) map (to: fn_ptr) map (tofrom: x)
+ for (int i = 0; i < N; i++)
+ x += (*fn_ptr[i]) ();
return x - expected;
}
diff --git a/libgomp/testsuite/libgomp.fortran/declare-target-indirect-2.f90 b/libgomp/testsuite/libgomp.fortran/declare-target-indirect-2.f90
index 34dd2778893..d3baa81dd07 100644
--- a/libgomp/testsuite/libgomp.fortran/declare-target-indirect-2.f90
+++ b/libgomp/testsuite/libgomp.fortran/declare-target-indirect-2.f90
@@ -1,5 +1,4 @@
! { dg-do run }
-! { dg-xfail-run-if "Requires libgomp bug fix pending review" { offload_device } }
module m
contains
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