[Openmp-commits] [openmp] f94b6f3 - [OpenMP] Remove optimization skipping reduction struct initialization (#65697)
via Openmp-commits
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Tue Sep 12 14:09:20 PDT 2023
Author: Rodrigo Ceccato de Freitas
Date: 2023-09-12T16:09:16-05:00
New Revision: f94b6f3396ce8b2c1575a4c459c4881381f0d5b1
URL: https://github.com/llvm/llvm-project/commit/f94b6f3396ce8b2c1575a4c459c4881381f0d5b1
DIFF: https://github.com/llvm/llvm-project/commit/f94b6f3396ce8b2c1575a4c459c4881381f0d5b1.diff
LOG: [OpenMP] Remove optimization skipping reduction struct initialization (#65697)
This commit removes an optimization that skips the initialization of the
reduction struct if the number of threads in a team is 1. This
optimization
caused a bug with Hidden Helper Threads. When the task group is
initially
initialized by the master thread but a Hidden Helper Thread executes a
target
nowait region, it requires the reduction struct initialization to
properly
accumulate the data.
This commit also adds a LIT test for issue #57522 to ensure that the
issue is
properly addressed and that the optimization removal does not introduce
any
regressions.
Fixes: #57522
Added:
openmp/libomptarget/test/offloading/task_in_reduction_target.c
Modified:
openmp/runtime/src/kmp_tasking.cpp
Removed:
################################################################################
diff --git a/openmp/libomptarget/test/offloading/task_in_reduction_target.c b/openmp/libomptarget/test/offloading/task_in_reduction_target.c
new file mode 100644
index 000000000000000..b546d73d544a584
--- /dev/null
+++ b/openmp/libomptarget/test/offloading/task_in_reduction_target.c
@@ -0,0 +1,31 @@
+// RUN: %libomptarget-compile-generic && \
+// RUN: %libomptarget-run-generic
+
+#include <omp.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+
+ int num_devices = omp_get_num_devices();
+
+ // No target devices, just return
+ if (num_devices == 0) {
+ printf("PASS\n");
+ return 0;
+ }
+
+ double sum = 999;
+ double A = 311;
+
+#pragma omp taskgroup task_reduction(+ : sum)
+ {
+#pragma omp target map(to : A) in_reduction(+ : sum) device(0) nowait
+ { sum += A; }
+ }
+
+ printf("PASS\n");
+ return EXIT_SUCCESS;
+}
+
+// CHECK: PASS
diff --git a/openmp/runtime/src/kmp_tasking.cpp b/openmp/runtime/src/kmp_tasking.cpp
index fefa609927e8933..e8eb6b02650377c 100644
--- a/openmp/runtime/src/kmp_tasking.cpp
+++ b/openmp/runtime/src/kmp_tasking.cpp
@@ -2512,7 +2512,7 @@ void *__kmp_task_reduction_init(int gtid, int num, T *data) {
KMP_ASSERT(tg != NULL);
KMP_ASSERT(data != NULL);
KMP_ASSERT(num > 0);
- if (nth == 1) {
+ if (nth == 1 && !__kmp_enable_hidden_helper) {
KA_TRACE(10, ("__kmpc_task_reduction_init: T#%d, tg %p, exiting nth=1\n",
gtid, tg));
return (void *)tg;
@@ -2699,6 +2699,7 @@ void *__kmpc_task_reduction_get_th_data(int gtid, void *tskgrp, void *data) {
return p_priv[tid];
}
}
+ KMP_ASSERT(tg->parent);
tg = tg->parent;
arr = (kmp_taskred_data_t *)(tg->reduce_data);
num = tg->reduce_num_data;
@@ -2711,7 +2712,10 @@ void *__kmpc_task_reduction_get_th_data(int gtid, void *tskgrp, void *data) {
// Called from __kmpc_end_taskgroup()
static void __kmp_task_reduction_fini(kmp_info_t *th, kmp_taskgroup_t *tg) {
kmp_int32 nth = th->th.th_team_nproc;
- KMP_DEBUG_ASSERT(nth > 1); // should not be called if nth == 1
+ KMP_DEBUG_ASSERT(
+ nth > 1 ||
+ __kmp_enable_hidden_helper); // should not be called if nth == 1 unless we
+ // are using hidden helper threads
kmp_taskred_data_t *arr = (kmp_taskred_data_t *)tg->reduce_data;
kmp_int32 num = tg->reduce_num_data;
for (int i = 0; i < num; ++i) {
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