[OpenMP] Fix tasking + parallel bug

From the bug report, the runtime needs to initialize the nproc variables
(inside middle init) for each root when the task is encountered, otherwise,
a segfault can occur.

Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=36720

Differential Revision: https://reviews.llvm.org/D49996

llvm-svn: 338313

1 files changed, 34 insertions, 0 deletions

diff --git a/openmp/runtime/test/tasking/bug_36720.c b/openmp/runtime/test/tasking/bug_36720.c
new file mode 100644
index 00000000000..059d9c94697
--- /dev/null
+++ b/openmp/runtime/test/tasking/bug_36720.c
@@ -0,0 +1,34 @@
+// RUN: %libomp-compile-and-run
+
+/*
+Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=36720
+
+Assertion failure at kmp_runtime.cpp(1715): nthreads > 0.
+OMP: Error #13: Assertion failure at kmp_runtime.cpp(1715).
+
+The assertion fails even with OMP_NUM_THREADS=1. If the second task is removed,
+everything runs to completion. If the "omp parallel for" directives are removed
+from inside the tasks, once again everything runs fine.
+*/
+
+#define N 1024
+
+int main() {
+  #pragma omp task
+  {
+    #pragma omp parallel for
+    for (int i = 0; i < N; i++)
+      (void)0;
+  }
+
+  #pragma omp task
+  {
+    #pragma omp parallel for
+    for (int i = 0; i < N; ++i)
+      (void)0;
+  }
+
+  #pragma omp taskwait
+
+  return 0;
+}