[OPENMP][NVPTX]Improve omp_get_max_threads() function.

Summary:
Function omp_get_max_threads() can always return 1 if current execution
mode is SPMD.

Reviewers: grokos, gtbercea, kkwli0

Subscribers: guansong, jdoerfert, caomhin, openmp-commits

Tags: #openmp

Differential Revision: https://reviews.llvm.org/D61379

llvm-svn: 359792

2 files changed, 48 insertions, 5 deletions

diff --git a/openmp/libomptarget/deviceRTLs/nvptx/src/libcall.cu b/openmp/libomptarget/deviceRTLs/nvptx/src/libcall.cu
index 3a0c39cb717..26b0f4e80a0 100644
--- a/openmp/libomptarget/deviceRTLs/nvptx/src/libcall.cu
+++ b/openmp/libomptarget/deviceRTLs/nvptx/src/libcall.cu
@@ -54,14 +54,11 @@ EXTERN int omp_get_num_threads(void) {
 }
 
 EXTERN int omp_get_max_threads(void) {
-  if (isRuntimeUninitialized()) {
-    ASSERT0(LT_FUSSY, isSPMDMode(),
-            "Expected SPMD mode only with uninitialized runtime.");
+  if (isSPMDMode())
     // We're already in parallel region.
     return 1;  // default is 1 thread avail
-  }
   omptarget_nvptx_TaskDescr *currTaskDescr =
-      getMyTopTaskDescriptor(isSPMDMode());
+      getMyTopTaskDescriptor(/*isSPMDExecutionMode=*/false);
   int rc = 1; // default is 1 thread avail
   if (!currTaskDescr->InParallelRegion()) {
     // Not currently in a parallel region, return what was set.
diff --git a/openmp/libomptarget/deviceRTLs/nvptx/test/api/max_threads.c b/openmp/libomptarget/deviceRTLs/nvptx/test/api/max_threads.c
new file mode 100644
index 00000000000..d0d9f315106
--- /dev/null
+++ b/openmp/libomptarget/deviceRTLs/nvptx/test/api/max_threads.c
@@ -0,0 +1,46 @@
+// RUN: %compile-run-and-check
+
+#include <omp.h>
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+  int MaxThreadsL1 = -1, MaxThreadsL2 = -1;
+
+#pragma omp declare reduction(unique:int                                       \
+                              : omp_out = (omp_in == 1 ? omp_in : omp_out))    \
+    initializer(omp_priv = -1)
+
+  // Non-SPMD mode.
+#pragma omp target teams map(MaxThreadsL1, MaxThreadsL2) thread_limit(32)      \
+    num_teams(1)
+  {
+    MaxThreadsL1 = omp_get_max_threads();
+#pragma omp parallel reduction(unique : MaxThreadsL2)
+    { MaxThreadsL2 = omp_get_max_threads(); }
+  }
+
+  // CHECK: Non-SPMD MaxThreadsL1 = 32
+  printf("Non-SPMD MaxThreadsL1 = %d\n", MaxThreadsL1);
+  // CHECK: Non-SPMD MaxThreadsL2 = 1
+  printf("Non-SPMD MaxThreadsL2 = %d\n", MaxThreadsL2);
+
+  // SPMD mode with full runtime
+  MaxThreadsL2 = -1;
+#pragma omp target parallel reduction(unique : MaxThreadsL2)
+  { MaxThreadsL2 = omp_get_max_threads(); }
+
+  // CHECK: SPMD with full runtime MaxThreadsL2 = 1
+  printf("SPMD with full runtime MaxThreadsL2 = %d\n", MaxThreadsL2);
+
+  // SPMD mode without runtime
+  MaxThreadsL2 = -1;
+#pragma omp target parallel for reduction(unique : MaxThreadsL2)
+  for (int I = 0; I < 2; ++I) {
+    MaxThreadsL2 = omp_get_max_threads();
+  }
+
+  // CHECK: SPMD without runtime MaxThreadsL2 = 1
+  printf("SPMD without runtime MaxThreadsL2 = %d\n", MaxThreadsL2);
+
+  return 0;
+}