[OPENMP] Resolve lost LoopTripCnt for subsequent loops in same thread.

Remove loopTripCnt from threaded device stack after consuming it.
Added a libomptarget DP message to aid in future debugging and to
validate the added testcase, which only runs in Debug build.

Differential Revision: https://reviews.llvm.org/D64808

llvm-svn: 366349

2 files changed, 41 insertions, 2 deletions

diff --git a/openmp/libomptarget/src/omptarget.cpp b/openmp/libomptarget/src/omptarget.cpp
index 39b5cb7da86..c41bf3167cc 100644
--- a/openmp/libomptarget/src/omptarget.cpp
+++ b/openmp/libomptarget/src/omptarget.cpp
@@ -732,8 +732,11 @@ int target(int64_t device_id, void *host_ptr, int32_t arg_num,
   uint64_t ltc = 0;
   TblMapMtx.lock();
   auto I = Device.LoopTripCnt.find(__kmpc_global_thread_num(NULL));
-  if (I != Device.LoopTripCnt.end())
-    std::swap(ltc, I->second);
+  if (I != Device.LoopTripCnt.end()) {
+    ltc = I->second;
+    Device.LoopTripCnt.erase(I);
+    DP("loop trip count is %lu.\n", ltc);
+  }
   TblMapMtx.unlock();
 
   // Launch device execution.
diff --git a/openmp/libomptarget/test/offloading/looptripcnt.c b/openmp/libomptarget/test/offloading/looptripcnt.c
new file mode 100644
index 00000000000..025231b0c6d
--- /dev/null
+++ b/openmp/libomptarget/test/offloading/looptripcnt.c
@@ -0,0 +1,36 @@
+// RUN: %libomptarget-compile-aarch64-unknown-linux-gnu && env LIBOMPTARGET_DEBUG=1 %libomptarget-run-aarch64-unknown-linux-gnu 2>&1 | %fcheck-aarch64-unknown-linux-gnu -allow-empty -check-prefix=DEBUG
+// RUN: %libomptarget-compile-powerpc64-ibm-linux-gnu && env LIBOMPTARGET_DEBUG=1 %libomptarget-run-powerpc64-ibm-linux-gnu 2>&1 | %fcheck-powerpc64-ibm-linux-gnu -allow-empty -check-prefix=DEBUG
+// RUN: %libomptarget-compile-powerpc64le-ibm-linux-gnu && env LIBOMPTARGET_DEBUG=1 %libomptarget-run-powerpc64le-ibm-linux-gnu 2>&1 | %fcheck-powerpc64le-ibm-linux-gnu -allow-empty -check-prefix=DEBUG
+// RUN: %libomptarget-compile-x86_64-pc-linux-gnu && env LIBOMPTARGET_DEBUG=1 %libomptarget-run-x86_64-pc-linux-gnu 2>&1 | %fcheck-x86_64-pc-linux-gnu -allow-empty -check-prefix=DEBUG
+// REQUIRES: libomptarget-debug
+
+/*
+  Test for looptripcount being popped from runtime stack.
+*/
+#include <stdio.h>
+#include <omp.h>
+int main()
+{
+  int N = 128;
+  int NN = 1024;
+  int num_teams[NN];
+  int num_threads[NN];
+
+  printf("#pragma omp target teams distribute parallel for thread_limit(4)\n");
+#pragma omp target teams distribute parallel for thread_limit(4)
+  for (int j = 0; j< N; j++) {
+    num_threads[j] = omp_get_num_threads();
+    num_teams[j] = omp_get_num_teams();
+  }
+  printf("num_threads %d num_teams %d\n", num_threads[0], num_teams[0]);
+// DEBUG: loop trip count is 128
+  printf("#pragma omp target teams distribute parallel for\n");
+#pragma omp target teams distribute parallel for
+  for (int j = 0; j< N; j++) {
+    num_threads[j] = omp_get_num_threads();
+    num_teams[j] = omp_get_num_teams();
+  }
+  printf("num_threads %d num_teams %d\n", num_threads[0], num_teams[0]);
+// DEBUG: loop trip count is 128
+  return 0;
+}