[Openmp-commits] [PATCH] D60223: [OpenMP][libomptarget] Add support for target link variables when unified memory is enabled

[Gheorghe-Teodor Bercea via Phabricator via Openmp-commits]

gtbercea created this revision.
gtbercea added reviewers: ABataev, AlexEichenberger.
Herald added subscribers: openmp-commits, jdoerfert, guansong.
Herald added a project: OpenMP.

Target link variables are currently implemented by creating a copy of the variables on the device side and unified memory never gets exploited.

When the prgram uses the:

  #pragma omp requires unified_shared_memory

directive in conjunction with a declare target link, the linked variable is no longer allocated on the device and the host version is used instead.

This behavior is overridden by performing an explicit mapping.

A Clang side patch is required.


Repository:
  rOMP OpenMP

https://reviews.llvm.org/D60223

Files:
  libomptarget/include/omptarget.h
  libomptarget/plugins/cuda/src/rtl.cpp
  libomptarget/src/device.cpp
  libomptarget/src/interface.cpp
  libomptarget/src/omptarget.cpp
  libomptarget/src/rtl.cpp


Index: libomptarget/src/rtl.cpp
===================================================================
--- libomptarget/src/rtl.cpp
+++ libomptarget/src/rtl.cpp
@@ -177,10 +177,6 @@
             DPxPTR(entry->addr));
         Device.PendingCtorsDtors[desc].PendingDtors.push_front(entry->addr);
       }
-
-      if (entry->flags & OMP_DECLARE_TARGET_LINK) {
-        DP("The \"link\" attribute is not yet supported!\n");
-      }
     }
     Device.PendingGlobalsMtx.unlock();
   }
Index: libomptarget/src/omptarget.cpp
===================================================================
--- libomptarget/src/omptarget.cpp
+++ libomptarget/src/omptarget.cpp
@@ -216,7 +216,8 @@
   for (int32_t i = 0; i < arg_num; ++i) {
     // Ignore private variables and arrays - there is no mapping for them.
     if ((arg_types[i] & OMP_TGT_MAPTYPE_LITERAL) ||
-        (arg_types[i] & OMP_TGT_MAPTYPE_PRIVATE))
+        (arg_types[i] & OMP_TGT_MAPTYPE_PRIVATE) ||
+        (arg_types[i] & OMP_TGT_MAPTYPE_USE_HOST_VAR))
       continue;
 
     void *HstPtrBegin = args[i];
Index: libomptarget/src/interface.cpp
===================================================================
--- libomptarget/src/interface.cpp
+++ libomptarget/src/interface.cpp
@@ -57,7 +57,7 @@
       }
       break;
     case tgt_default:
-        FATAL_MESSAGE0(1, "default offloading policy must switched to " 
+        FATAL_MESSAGE0(1, "default offloading policy must switched to "
             "mandatory or disabled");
       break;
     case tgt_mandatory:
Index: libomptarget/src/device.cpp
===================================================================
--- libomptarget/src/device.cpp
+++ libomptarget/src/device.cpp
@@ -152,7 +152,7 @@
 
 // Used by target_data_begin
 // Return the target pointer begin (where the data will be moved).
-// Allocate memory if this is the first occurrence if this mapping.
+// Allocate memory if this is the first occurrence of this mapping.
 // Increment the reference counter.
 // If NULL is returned, then either data allocation failed or the user tried
 // to do an illegal mapping.
Index: libomptarget/plugins/cuda/src/rtl.cpp
===================================================================
--- libomptarget/plugins/cuda/src/rtl.cpp
+++ libomptarget/plugins/cuda/src/rtl.cpp
@@ -434,7 +434,18 @@
 
       DP("Entry point " DPxMOD " maps to global %s (" DPxMOD ")\n",
           DPxPTR(e - HostBegin), e->name, DPxPTR(cuptr));
+
       entry.addr = (void *)cuptr;
+      if (e->flags & OMP_DECLARE_TARGET_LINK) {
+        // By default, we handle declare target link global variables as if
+        // unified memory can be sued. If at target region launch it turns
+        // out that unified memory is not available then this value will
+        // be overwritten.
+        cuMemcpyHtoD(cuptr, e->addr, 8);
+        DP("Copy linked variable host address (" DPxMOD ")"
+           "to device address (" DPxMOD ")\n",
+          DPxPTR(*((void**)e->addr)), DPxPTR(cuptr));
+      }
 
       DeviceInfo.addOffloadEntry(device_id, entry);
 
Index: libomptarget/include/omptarget.h
===================================================================
--- libomptarget/include/omptarget.h
+++ libomptarget/include/omptarget.h
@@ -47,6 +47,8 @@
   OMP_TGT_MAPTYPE_LITERAL         = 0x100,
   // mapping is implicit
   OMP_TGT_MAPTYPE_IMPLICIT        = 0x200,
+  /// Target link
+  OMP_TGT_MAPTYPE_USE_HOST_VAR    = 0x400,
   // member of struct, member given by [16 MSBs] - 1
   OMP_TGT_MAPTYPE_MEMBER_OF       = 0xffff000000000000
 };


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