Switch back to the GPUIDX macro (#9438)

tests/cpp/helpers.h

@@ -34,6 +34,12 @@
 #define DeclareUnifiedTest(name) name
 #endif
 
+#if defined(__CUDACC__)
+#define GPUIDX (common::AllVisibleGPUs() == 1 ? 0 : collective::GetRank())
+#else
+#define GPUIDX (-1)
+#endif
+
 #if defined(__CUDACC__)
 #define DeclareUnifiedDistributedTest(name) MGPU ## name
 #else
@@ -540,15 +546,6 @@ void RunWithInMemoryCommunicator(int32_t world_size, Function&& function, Args&&
 #endif
 }
 
-inline int GetGPUId() {
-#if defined(__CUDACC__)
-  auto const n_gpus = common::AllVisibleGPUs();
-  return n_gpus == 1 ? 0 : collective::GetRank();
-#else
-  return -1;
-#endif
-}
-
 class BaseMGPUTest : public ::testing::Test {
  protected:
   int world_size_;