[libomptarget] [amdgpu] Change default number of teams per computation unit

[dhruvachak]

Summary

This patch is related to https://reviews.llvm.org/D98832. Based on discussions there, I decided to separate out the teams default as this patch. This change is to increase the number of teams per computation unit so as to provide more wavefronts for hiding latency. This change improves performance for some programs, including 20-50% for some Stream benchmarks.

[JonChesterfield]

LG, thanks

[dhruvachak]

rebase

openmp/libomptarget/plugins/amdgpu/src/rtl.cpp

 hostrpc_assign_buffer(hsa_agent_t, hsa_queue_t *, uint32_t device_id) {
   DP("Warning: Attempting to assign hostrpc to device %u, but hostrpc library "
      "missing\n",
      device_id);
   return 0;
 }
 }
 
+// Heuristic parameters used for kernel launch
+// Number of teams per CU to allow scheduling flexibility
+static const unsigned DefaultTeamsPerCU = 4;
+
 int print_kernel_trace;
 
 #ifdef OMPTARGET_DEBUG
 #define check(msg, status)                                                     \
   if (status != HSA_STATUS_SUCCESS) {                                          \
     DP(#msg " failed\n");                                                      \
   } else {                                                                     \
     DP(#msg " succeeded\n");                                                   \
int32_t __tgt_rtl_init_device(int device_id) {
 
   // Set default number of teams
   if (DeviceInfo.EnvNumTeams > 0) {
     DeviceInfo.NumTeams[device_id] = DeviceInfo.EnvNumTeams;
     DP("Default number of teams set according to environment %d\n",
        DeviceInfo.EnvNumTeams);
   } else {
     char *TeamsPerCUEnvStr = getenv("OMP_TARGET_TEAMS_PER_PROC");
-    int TeamsPerCU = 1; // default number of teams per CU is 1
+    int TeamsPerCU = DefaultTeamsPerCU;
     if (TeamsPerCUEnvStr) {
       TeamsPerCU = std::stoi(TeamsPerCUEnvStr);
     }
 
     DeviceInfo.NumTeams[device_id] =
         TeamsPerCU * DeviceInfo.ComputeUnits[device_id];
     DP("Default number of teams = %d * number of compute units %d\n",
        TeamsPerCU, DeviceInfo.ComputeUnits[device_id]);