[OpenMP] [OMPT] [amdgpu] [4/8] Implemented callback registration in nextgen plugins

The purpose of this patch is to Implement registration of callback functions in the generic plugin by looking up corresponding callbacks in libomptarget. The overall design document is https://rice.app.box.com/s/pf3gix2hs4d4o1aatwir1set05xmjljc

Defined an object of type OmptDeviceCallbacksTy in the amdgpu plugin for holding the tool-provided callback functions. Implemented a global constructor in the plugin that creates a connector object to connect with libomptarget. The callbacks that are already registered with libomptarget are looked up and registered with the plugin.

Combined with an internal patch from Dhruva Chakrabarti, which fixes the OMPT initialization ordering.
Achieved through removal of the constructor attribute from ompt_init.

Patch from John Mellor-Crummey <johnmc@rice.edu>
With contributions from:
Dhruva Chakrabarti <Dhruva.Chakrabarti@amd.com>
Michael Halkenhaeuser <MichaelGerald.Halkenhauser@amd.com>

Differential Revision: https://reviews.llvm.org/D124070

12 files changed, 245 insertions, 13 deletions

diff --git a/openmp/libomptarget/include/ompt_device_callbacks.h b/openmp/libomptarget/include/ompt_device_callbacks.h
index 3dbba3dedbee..127e18950249 100644
--- a/openmp/libomptarget/include/ompt_device_callbacks.h
+++ b/openmp/libomptarget/include/ompt_device_callbacks.h
@@ -49,6 +49,20 @@ public:
 #undef OmptBindCallback
   }
 
+  /// Used to find a callback given its name
+  ompt_interface_fn_t lookupCallback(const char *InterfaceFunctionName) {
+#define OmptLookup(Name, Type, Code)                                           \
+  if (strcmp(InterfaceFunctionName, #Name) == 0)                               \
+    return (ompt_interface_fn_t)Name##_fn;
+
+    FOREACH_OMPT_TARGET_CALLBACK(OmptLookup);
+#undef OmptLookup
+    return (ompt_interface_fn_t) nullptr;
+  }
+
+  /// Wrapper function to find a callback given its name
+  static ompt_interface_fn_t doLookup(const char *InterfaceFunctionName);
+
 private:
   /// Set to true if callbacks for this library have been initialized
   bool Enabled;
@@ -62,8 +76,6 @@ private:
 /// Device callbacks object for the library that performs the instantiation
 extern OmptDeviceCallbacksTy OmptDeviceCallbacks;
 
-#undef DEBUG_PREFIX
-
 #endif // OMPT_SUPPORT
 
 #endif // _OMPT_DEVICE_CALLBACKS_H
diff --git a/openmp/libomptarget/plugins-nextgen/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/CMakeLists.txt
index af02f050f467..a51da395680b 100644
--- a/openmp/libomptarget/plugins-nextgen/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/CMakeLists.txt
@@ -49,6 +49,7 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "${tmachine}$")
         PRIVATE
         elf_common
         MemoryManager
+        OMPT
         PluginInterface
         ${LIBOMPTARGET_DEP_LIBFFI_LIBRARIES}
         ${OPENMP_PTHREAD_LIB}
diff --git a/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
index b689ff5a38d5..0c807a402c68 100644
--- a/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/amdgpu/CMakeLists.txt
@@ -82,6 +82,7 @@ add_llvm_library(omptarget.rtl.amdgpu.nextgen SHARED
   PRIVATE
   elf_common
   MemoryManager
+  OMPT
   PluginInterface
   ${LIBOMPTARGET_DEP_LIBRARIES}
   ${OPENMP_PTHREAD_LIB}
diff --git a/openmp/libomptarget/plugins-nextgen/common/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/common/CMakeLists.txt
index 1c5594eec5af..f0645d0d1753 100644
--- a/openmp/libomptarget/plugins-nextgen/common/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/common/CMakeLists.txt
@@ -10,4 +10,5 @@
 #
 ##===----------------------------------------------------------------------===##
 
+add_subdirectory(OMPT)
 add_subdirectory(PluginInterface)
diff --git a/openmp/libomptarget/plugins-nextgen/common/OMPT/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/common/OMPT/CMakeLists.txt
new file mode 100644
index 000000000000..c50dd18dce02
--- /dev/null
+++ b/openmp/libomptarget/plugins-nextgen/common/OMPT/CMakeLists.txt
@@ -0,0 +1,72 @@
+##===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+##===----------------------------------------------------------------------===##
+#
+# Aggregation of parts which can be used by OpenMP tools
+#
+##===----------------------------------------------------------------------===##
+
+# NOTE: Don't try to build `OMPT` using `add_llvm_library` because we
+# don't want to export `OMPT` while `add_llvm_library` requires that.
+add_library(OMPT OBJECT
+  OmptCallback.cpp)
+
+# This is required when using LLVM libraries.
+llvm_update_compile_flags(OMPT)
+
+if (LLVM_LINK_LLVM_DYLIB)
+  set(llvm_libs LLVM)
+else()
+  llvm_map_components_to_libnames(llvm_libs
+    ${LLVM_TARGETS_TO_BUILD}
+    AggressiveInstCombine
+    Analysis
+    BinaryFormat
+    BitReader
+    BitWriter
+    CodeGen
+    Core
+    Extensions
+    InstCombine
+    Instrumentation
+    IPO
+    IRReader
+    Linker
+    MC
+    Object
+    Passes
+    Remarks
+    ScalarOpts
+    Support
+    Target
+    TargetParser
+    TransformUtils
+    Vectorize
+  )
+endif()
+
+target_link_libraries(OMPT
+  PUBLIC
+    ${llvm_libs}
+    elf_common
+    MemoryManager
+)
+
+# Define the TARGET_NAME and DEBUG_PREFIX.
+target_compile_definitions(OMPT PRIVATE
+  TARGET_NAME="OMPT"
+  DEBUG_PREFIX="OMPT"
+)
+
+target_include_directories(OMPT
+  INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${LIBOMPTARGET_INCLUDE_DIR}
+)
+
+set_target_properties(OMPT PROPERTIES
+  POSITION_INDEPENDENT_CODE ON
+  CXX_VISIBILITY_PRESET protected)
diff --git a/openmp/libomptarget/plugins-nextgen/common/OMPT/OmptCallback.cpp b/openmp/libomptarget/plugins-nextgen/common/OMPT/OmptCallback.cpp
new file mode 100644
index 000000000000..eb47f10a3f41
--- /dev/null
+++ b/openmp/libomptarget/plugins-nextgen/common/OMPT/OmptCallback.cpp
@@ -0,0 +1,83 @@
+//===---------- OmptCallback.cpp - Generic OMPT callbacks --------- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// OMPT support for PluginInterface
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef OMPT_SUPPORT
+#include <atomic>
+#include <cstdio>
+#include <string.h>
+#include <vector>
+
+#include "Debug.h"
+#include "ompt_connector.h"
+#include "ompt_device_callbacks.h"
+
+/// Object maintaining all the callbacks in the plugin
+OmptDeviceCallbacksTy OmptDeviceCallbacks;
+
+/// Lookup function used for querying callback functions maintained
+/// by the plugin
+ompt_interface_fn_t
+OmptDeviceCallbacksTy::doLookup(const char *InterfaceFunctionName) {
+  // TODO This will be populated with device tracing functions
+  return (ompt_interface_fn_t) nullptr;
+}
+
+/// Used to indicate whether OMPT was enabled for this library
+static bool OmptEnabled = false;
+
+/// This function is passed to libomptarget as part of the OMPT connector
+/// object. It is called by libomptarget during initialization of OMPT in the
+/// plugin. \p lookup to be used to query callbacks registered with libomptarget
+/// \p initial_device_num Initial device num provided by libomptarget
+/// \p tool_data as provided by the tool
+static int OmptDeviceInit(ompt_function_lookup_t lookup, int initial_device_num,
+                          ompt_data_t *tool_data) {
+  DP("OMPT: Enter OmptDeviceInit\n");
+  OmptEnabled = true;
+  // The lookup parameter is provided by libomptarget which already has the tool
+  // callbacks registered at this point. The registration call below causes the
+  // same callback functions to be registered in the plugin as well.
+  OmptDeviceCallbacks.registerCallbacks(lookup);
+  DP("OMPT: Exit OmptDeviceInit\n");
+  return 0;
+}
+
+/// This function is passed to libomptarget as part of the OMPT connector
+/// object. It is called by libomptarget during finalization of OMPT in the
+/// plugin.
+static void OmptDeviceFini(ompt_data_t *tool_data) {
+  DP("OMPT: Executing OmptDeviceFini\n");
+}
+
+/// Used to initialize callbacks implemented by the tool. This interface will
+/// lookup the callbacks table in libomptarget and assign them to the callbacks
+/// table maintained in the calling plugin library.
+void OmptCallbackInit() {
+  DP("OMPT: Entering OmptCallbackInit\n");
+  /// Connect plugin instance with libomptarget
+  OmptLibraryConnectorTy LibomptargetConnector("libomptarget");
+  ompt_start_tool_result_t OmptResult;
+
+  // Initialize OmptResult with the init and fini functions that will be
+  // called by the connector
+  OmptResult.initialize = OmptDeviceInit;
+  OmptResult.finalize = OmptDeviceFini;
+  OmptResult.tool_data.value = 0;
+
+  // Initialize the device callbacks first
+  OmptDeviceCallbacks.init();
+
+  // Now call connect that causes the above init/fini functions to be called
+  LibomptargetConnector.connect(&OmptResult);
+  DP("OMPT: Exiting OmptCallbackInit\n");
+}
+#endif
diff --git a/openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt
index 91d64f429823..c3950aff6187 100644
--- a/openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/common/PluginInterface/CMakeLists.txt
@@ -60,6 +60,7 @@ target_link_libraries(PluginInterface
     ${llvm_libs}
     elf_common
     MemoryManager
+    OMPT
 )
 
 # Define the TARGET_NAME and DEBUG_PREFIX.
diff --git a/openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt b/openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt
index 397b06b67692..0ae1ddff5541 100644
--- a/openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt
+++ b/openmp/libomptarget/plugins-nextgen/cuda/CMakeLists.txt
@@ -36,6 +36,7 @@ add_llvm_library(omptarget.rtl.cuda.nextgen SHARED
   LINK_LIBS PRIVATE
   elf_common
   MemoryManager
+  OMPT
   PluginInterface
   ${OPENMP_PTHREAD_LIB}
 
diff --git a/openmp/libomptarget/src/CMakeLists.txt b/openmp/libomptarget/src/CMakeLists.txt
index ef3a6270b78a..425121c9ef10 100644
--- a/openmp/libomptarget/src/CMakeLists.txt
+++ b/openmp/libomptarget/src/CMakeLists.txt
@@ -20,7 +20,7 @@ add_llvm_library(omptarget
   interface.cpp
   interop.cpp
   omptarget.cpp
-  ompt_callback.cpp
+  OmptCallback.cpp
   rtl.cpp
   LegacyAPI.cpp
 
diff --git a/openmp/libomptarget/src/ompt_callback.cpp b/openmp/libomptarget/src/OmptCallback.cpp
index 5715642ad3a9..2cfa487b123f 100644
--- a/openmp/libomptarget/src/ompt_callback.cpp
+++ b/openmp/libomptarget/src/OmptCallback.cpp
@@ -1,4 +1,4 @@
-//===-- ompt_callback.cpp - Target independent OpenMP target RTL -- C++ -*-===//
+//===-- OmptCallback.cpp - Target independent OpenMP target RTL --- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -19,6 +19,7 @@
 
 #include "omp-tools.h"
 
+#include "Debug.h"
 #include "ompt_connector.h"
 #include "ompt_device_callbacks.h"
 #include "private.h"
@@ -26,10 +27,39 @@
 #define fnptr_to_ptr(x) ((void *)(uint64_t)x)
 
 /// Used to indicate whether OMPT was enabled for this library
-bool ompt_enabled = false;
+bool OmptEnabled = false;
 /// Object maintaining all the callbacks for this library
 OmptDeviceCallbacksTy OmptDeviceCallbacks;
 
+/// Used to maintain the finalization function that is received
+/// from the plugin during connect
+class LibomptargetRtlFinalizer {
+public:
+  LibomptargetRtlFinalizer() : RtlFinalization(nullptr) {}
+  void registerRtl(ompt_finalize_t FinalizationFunction) {
+    assert((RtlFinalization == nullptr) &&
+           "RTL finalization may only be registered once");
+    RtlFinalization = FinalizationFunction;
+  }
+  void finalize() {
+    if (RtlFinalization)
+      RtlFinalization(nullptr /* tool_data */);
+    RtlFinalization = nullptr;
+  }
+
+private:
+  ompt_finalize_t RtlFinalization;
+};
+
+/// Object that will maintain the RTL finalizer from the plugin
+static LibomptargetRtlFinalizer LibraryFinalizer;
+
+/// Lookup function to be used by libomptarget library
+ompt_interface_fn_t
+OmptDeviceCallbacksTy::doLookup(const char *InterfaceFunctionName) {
+  return OmptDeviceCallbacks.lookupCallback(InterfaceFunctionName);
+}
+
 /// This is the function called by the higher layer (libomp) responsible
 /// for initializing OMPT in this library. This is passed to libomp
 /// as part of the OMPT connector object.
@@ -40,7 +70,7 @@ static int ompt_libomptarget_initialize(ompt_function_lookup_t lookup,
                                         int initial_device_num,
                                         ompt_data_t *tool_data) {
   DP("enter ompt_libomptarget_initialize!\n");
-  ompt_enabled = true;
+  OmptEnabled = true;
   // The lookup parameter is provided by libomp which already has the
   // tool callbacks registered at this point. The registration call
   // below causes the same callback functions to be registered in
@@ -50,9 +80,14 @@ static int ompt_libomptarget_initialize(ompt_function_lookup_t lookup,
   return 0;
 }
 
+/// This function is passed to libomp as part of the OMPT connector object.
+/// It is called by libomp during finalization of OMPT in libomptarget.
 static void ompt_libomptarget_finalize(ompt_data_t *data) {
   DP("enter ompt_libomptarget_finalize!\n");
-  ompt_enabled = false;
+  // Before disabling OMPT, call the finalizer (of the plugin) that was
+  // registered with this library
+  LibraryFinalizer.finalize();
+  OmptEnabled = false;
   DP("exit ompt_libomptarget_finalize!\n");
 }
 
@@ -61,11 +96,9 @@ static void ompt_libomptarget_finalize(ompt_data_t *data) {
  *****************************************************************************/
 /// Used to initialize callbacks implemented by the tool. This interface
 /// will lookup the callbacks table in libomp and assign them to the callbacks
-/// maintained in libomptarget. Using priority 102 to have this constructor
-/// run after the init target library constructor with priority 101 (see
-/// rtl.cpp).
-__attribute__((constructor(102))) static void ompt_init(void) {
-  DP("OMPT: Enter ompt_init\n");
+/// maintained in libomptarget.
+void InitOmptLibomp() {
+  DP("OMPT: Enter InitOmptLibomp\n");
   // Connect with libomp
   static OmptLibraryConnectorTy LibompConnector("libomp");
   static ompt_start_tool_result_t OmptResult;
@@ -81,7 +114,24 @@ __attribute__((constructor(102))) static void ompt_init(void) {
 
   // Now call connect that causes the above init/fini functions to be called
   LibompConnector.connect(&OmptResult);
-  DP("OMPT: Exit ompt_init\n");
+  DP("OMPT: Exit InitOmptLibomp\n");
 }
 
 #endif // OMPT_SUPPORT
+
+extern "C" {
+/// Used for connecting libomptarget with a plugin
+void ompt_libomptarget_connect(ompt_start_tool_result_t *result) {
+  DP("OMPT: Enter ompt_libomptarget_connect\n");
+  if (OmptEnabled && result) {
+    // Cache the fini function so that it can be invoked on exit
+    LibraryFinalizer.registerRtl(result->finalize);
+    // Invoke the provided init function with the lookup function maintained
+    // in this library so that callbacks maintained by this library are
+    // retrieved.
+    result->initialize(OmptDeviceCallbacksTy::doLookup,
+                       0 /* initial_device_num */, nullptr /* tool_data */);
+  }
+  DP("OMPT: Leave ompt_libomptarget_connect\n");
+}
+}
diff --git a/openmp/libomptarget/src/exports b/openmp/libomptarget/src/exports
index 6c3fdf0950ab..48591dd6c3fa 100644
--- a/openmp/libomptarget/src/exports
+++ b/openmp/libomptarget/src/exports
@@ -64,6 +64,7 @@ VERS1.0 {
     __tgt_interop_init;
     __tgt_interop_use;
     __tgt_interop_destroy;
+    ompt_libomptarget_connect;
   local:
     *;
 };
diff --git a/openmp/libomptarget/src/rtl.cpp b/openmp/libomptarget/src/rtl.cpp
index 9c7cc355d054..5360d9784cb6 100644
--- a/openmp/libomptarget/src/rtl.cpp
+++ b/openmp/libomptarget/src/rtl.cpp
@@ -43,6 +43,10 @@ PluginManager *PM;
 
 static char *ProfileTraceFile = nullptr;
 
+#ifdef OMPT_SUPPORT
+extern void InitOmptLibomp();
+#endif
+
 __attribute__((constructor(101))) void init() {
   DP("Init target library!\n");
 
@@ -65,6 +69,11 @@ __attribute__((constructor(101))) void init() {
   if (ProfileTraceFile)
     timeTraceProfilerInitialize(500 /* us */, "libomptarget");
 
+  #ifdef OMPT_SUPPORT
+    // Initialize OMPT first
+    InitOmptLibomp();
+  #endif
+
   PM->RTLs.loadRTLs();
   PM->registerDelayedLibraries();
 }