[libomptarget] Move AMD system checks for host globals in separate function.

This patch is supposed to land before Joseph's upstream patch:
llvm#77150

Change-Id: I71cddcdeb7181caa02361ce19873bbbf5bde9578

Author: doru1004

openmp/libomptarget/include/Shared/PluginAPI.h

@@ -246,6 +246,8 @@ bool __tgt_rtl_requested_prepopulate_gpu_page_table();
 // Check if image is incompatible due to XNACK mismatch.
 void __tgt_rtl_check_invalid_image(__tgt_device_image *Image);
 
+bool __tgt_rtl_can_use_host_globals();
+
 bool __tgt_rtl_is_system_supporting_managed_memory();
 
 int32_t __tgt_rtl_launch_kernel_sync(int32_t, void *, void **, ptrdiff_t *,

openmp/libomptarget/include/Shared/PluginAPI.inc

@@ -48,6 +48,7 @@ PLUGIN_API_HANDLE(data_notify_unmapped, false);
 PLUGIN_API_HANDLE(set_device_offset, false);
 PLUGIN_API_HANDLE(initialize_record_replay, false);
 PLUGIN_API_HANDLE(check_invalid_image, true);
+PLUGIN_API_HANDLE(can_use_host_globals, true);
 PLUGIN_API_HANDLE(has_apu_device, true);
 PLUGIN_API_HANDLE(has_USM_capable_dGPU, true);
 PLUGIN_API_HANDLE(are_allocations_for_maps_on_apus_disabled, true);

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

@@ -4179,6 +4179,31 @@ struct AMDGPUPluginTy final : public GenericPluginTy {
     return;
   }
 
+  bool canUseHostGlobals() {
+    // Check if the HSA_XNACK and OMPX_APU_MAPS are enabled. If unified memory is
+    // not enabled but both HSA_XNACK and OMPX_APU_MAPS are enabled then we can
+    // also use globals directly from the host.
+    bool EnableHostGlobals = false;
+    bool IsZeroCopyOnAPU = Plugin::get().AreAllocationsForMapsOnApusDisabled();
+    BoolEnvar HSAXnack = BoolEnvar("HSA_XNACK", false);
+
+    if (IsZeroCopyOnAPU && HSAXnack.get())
+      EnableHostGlobals = true;
+
+    // Check if we are on a system that has an APU or on a non-APU system
+    // where unified shared memory can be enabled:
+    bool IsUsmSystem =
+        Plugin::get().hasAPUDevice() || Plugin::get().hasDGpuWithUsmSupport();
+
+    // Warn user if there is a mismatch between the request and the system
+    // architecture:
+    if (EnableHostGlobals && !IsUsmSystem)
+      fprintf(stderr, "OMPX_APU_MAPS and HSA_XNACK enabled on system that"
+                      " does not support unified shared memory");
+
+    return IsUsmSystem && EnableHostGlobals;
+  }
+
   bool isDataExchangable(int32_t SrcDeviceId, int32_t DstDeviceId) override {
     return true;
   }

openmp/libomptarget/plugins-nextgen/common/include/PluginInterface.h

@@ -1182,6 +1182,10 @@ struct GenericPluginTy {
   /// Indicate whether the plugin supports empty images.
   virtual bool supportsEmptyImages() const { return false; }
 
+  /// Return true if host globals can be enabled on a system that supprots
+  /// unified shared memory.
+  virtual bool canUseHostGlobals() const {}
+
 protected:
   /// Indicate whether a device id is valid.
   bool isValidDeviceId(int32_t DeviceId) const {

openmp/libomptarget/plugins-nextgen/common/src/PluginInterface.cpp

@@ -1116,30 +1116,8 @@ Error GenericDeviceTy::registerGlobalOffloadEntry(
   // can either be link or to. This means that once unified
   // memory is activated via the requires directive, the variable
   // can be used directly from the host in both cases.
-
-  // Check if the HSA_XNACK and OMPX_APU_MAPS are enabled. If unified memory is
-  // not enabled but both HSA_XNACK and OMPX_APU_MAPS are enabled then we can
-  // also use globals directly from the host.
-  bool EnableHostGlobals = false;
-  bool IsZeroCopyOnAPU = Plugin::get().AreAllocationsForMapsOnApusDisabled();
-  BoolEnvar HSAXnack = BoolEnvar("HSA_XNACK", false);
-
-  if (IsZeroCopyOnAPU && HSAXnack.get())
-    EnableHostGlobals = true;
-
-  // Check if we are on a system that has an APU or on a non-APU system
-  // where unified shared memory can be enabled:
-  bool IsUsmSystem =
-      Plugin::get().hasAPUDevice() || Plugin::get().hasDGpuWithUsmSupport();
-
-  // Fail if there is a mismatch between the user request and the system
-  // architecture:
-  if (EnableHostGlobals && !IsUsmSystem)
-    return Plugin::error("OMPX_APU_MAPS and HSA_XNACK enabled on system that"
-                         " does not support unified shared memory");
-
   if (Plugin.getRequiresFlags() & OMP_REQ_UNIFIED_SHARED_MEMORY ||
-      (IsUsmSystem && EnableHostGlobals)) {
+      Plugin.canUseHostGlobals()) {
     // If unified memory is present any target link or to variables
     // can access host addresses directly. There is no longer a
     // need for device copies.
@@ -1828,6 +1806,10 @@ void __tgt_rtl_check_invalid_image(__tgt_device_image *InvalidImage) {
   Plugin::get().checkInvalidImage(InvalidImage);
 }
 
+bool __tgt_rtl_can_use_host_globals() {
+  return Plugin::get().canUseHostGlobals();
+}
+
 int32_t __tgt_rtl_supports_empty_images() {
   return Plugin::get().supportsEmptyImages();
 }