[Offload] Provide a kernel library useable by the offload runtime

As mentioned in llvm#68706, it is useful to be able to call kernels from the
runtime, e.g., to perform memset. This patch provides a kernel library
that can be invoked from the offload runtime directly.

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -1202,8 +1202,11 @@ bool tools::addOpenMPRuntime(const Compilation &C, ArgStringList &CmdArgs,
                     options::OPT_fno_openmp, false)) {
     // We need libomptarget (liboffload) if it's the choosen offloading runtime.
     if (Args.hasFlag(options::OPT_foffload_via_llvm,
-                     options::OPT_fno_offload_via_llvm, false))
+                     options::OPT_fno_offload_via_llvm, false)) {
       CmdArgs.push_back("-lomptarget");
+      if (!Args.hasArg(options::OPT_nogpulib))
+        CmdArgs.append({"-lomptarget.devicertl", "-loffload.kernels"});
+    }
     return false;
   }
 
@@ -1240,7 +1243,7 @@ bool tools::addOpenMPRuntime(const Compilation &C, ArgStringList &CmdArgs,
     CmdArgs.push_back("-lomptarget");
 
   if (IsOffloadingHost && !Args.hasArg(options::OPT_nogpulib))
-    CmdArgs.push_back("-lomptarget.devicertl");
+    CmdArgs.append({"-lomptarget.devicertl", "-loffload.kernels"});
 
   addArchSpecificRPath(TC, Args, CmdArgs);
 

offload/DeviceRTL/CMakeLists.txt

@@ -69,6 +69,7 @@ elseif(LIBOMPTARGET_DEVICE_ARCHITECTURES STREQUAL "auto" OR
       "${LIBOMPTARGET_NVPTX_DETECTED_ARCH_LIST};${LIBOMPTARGET_AMDGPU_DETECTED_ARCH_LIST}")
 endif()
 list(REMOVE_DUPLICATES LIBOMPTARGET_DEVICE_ARCHITECTURES)
+set(LIBOMPTARGET_DEVICE_ARCHITECTURES ${LIBOMPTARGET_DEVICE_ARCHITECTURES} PARENT_SCOPE)
 
 set(include_files
   ${include_directory}/Allocator.h

offload/include/device.h

@@ -124,6 +124,9 @@ struct DeviceTy {
   /// Calls the corresponding print device info function in the plugin.
   bool printDeviceInfo();
 
+  /// Return the handle to the kernel with name \p Name in \p HandlePtr.
+  int32_t getKernelHandle(llvm::StringRef Name, void **HandlePtr);
+
   /// Event related interfaces.
   /// {
   /// Create an event.

offload/include/omptarget.h

@@ -400,6 +400,11 @@ void __tgt_target_data_update_nowait_mapper(
 int __tgt_target_kernel(ident_t *Loc, int64_t DeviceId, int32_t NumTeams,
                         int32_t ThreadLimit, void *HostPtr, KernelArgsTy *Args);
 
+/// Launch the kernel \p KernelName with a CUDA style launch and the given grid
+/// sizes and arguments (\p KernelArgs).
+int __tgt_launch_by_name(ident_t *Loc, int64_t DeviceId, const char *KernelName,
+		      KernelArgsTy *KernelArgs);
+
 // Non-blocking synchronization for target nowait regions. This function
 // acquires the asynchronous context from task data of the current task being
 // executed and tries to query for the completion of its operations. If the

offload/plugins-nextgen/amdgpu/src/rtl.cpp

@@ -2016,20 +2016,13 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
     return Plugin::success();
   }
 
-  virtual Error callGlobalConstructors(GenericPluginTy &Plugin,
-                                       DeviceImageTy &Image) override {
-    GenericGlobalHandlerTy &Handler = Plugin.getGlobalHandler();
-    if (Handler.isSymbolInImage(*this, Image, "amdgcn.device.fini"))
-      Image.setPendingGlobalDtors();
-
-    return callGlobalCtorDtorCommon(Plugin, Image, /*IsCtor=*/true);
+  virtual Expected<StringRef>
+  getGlobalConstructorName(DeviceImageTy &Image) override {
+    return "amdgcn.device.init";
   }
-
-  virtual Error callGlobalDestructors(GenericPluginTy &Plugin,
-                                      DeviceImageTy &Image) override {
-    if (Image.hasPendingGlobalDtors())
-      return callGlobalCtorDtorCommon(Plugin, Image, /*IsCtor=*/false);
-    return Plugin::success();
+  virtual Expected<StringRef>
+  getGlobalDestructorName(DeviceImageTy &Image) override {
+    return "amdgcn.device.fini";
   }
 
   uint64_t getStreamBusyWaitMicroseconds() const { return OMPX_StreamBusyWait; }
@@ -2107,13 +2100,14 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
   uint64_t getClockFrequency() const override { return ClockFrequency; }
 
   /// Allocate and construct an AMDGPU kernel.
-  Expected<GenericKernelTy &> constructKernel(const char *Name) override {
+  Expected<GenericKernelTy &>
+  constructKernelImpl(llvm::StringRef Name) override {
     // Allocate and construct the AMDGPU kernel.
     AMDGPUKernelTy *AMDGPUKernel = Plugin.allocate<AMDGPUKernelTy>();
     if (!AMDGPUKernel)
       return Plugin::error("Failed to allocate memory for AMDGPU kernel");
 
-    new (AMDGPUKernel) AMDGPUKernelTy(Name);
+    new (AMDGPUKernel) AMDGPUKernelTy(Name.data());
 
     return *AMDGPUKernel;
   }
@@ -2791,38 +2785,6 @@ struct AMDGPUDeviceTy : public GenericDeviceTy, AMDGenericDeviceTy {
   using AMDGPUEventRef = AMDGPUResourceRef<AMDGPUEventTy>;
   using AMDGPUEventManagerTy = GenericDeviceResourceManagerTy<AMDGPUEventRef>;
 
-  /// Common method to invoke a single threaded constructor or destructor
-  /// kernel by name.
-  Error callGlobalCtorDtorCommon(GenericPluginTy &Plugin, DeviceImageTy &Image,
-                                 bool IsCtor) {
-    const char *KernelName =
-        IsCtor ? "amdgcn.device.init" : "amdgcn.device.fini";
-    // Perform a quick check for the named kernel in the image. The kernel
-    // should be created by the 'amdgpu-lower-ctor-dtor' pass.
-    GenericGlobalHandlerTy &Handler = Plugin.getGlobalHandler();
-    if (IsCtor && !Handler.isSymbolInImage(*this, Image, KernelName))
-      return Plugin::success();
-
-    // Allocate and construct the AMDGPU kernel.
-    AMDGPUKernelTy AMDGPUKernel(KernelName);
-    if (auto Err = AMDGPUKernel.init(*this, Image))
-      return Err;
-
-    AsyncInfoWrapperTy AsyncInfoWrapper(*this, nullptr);
-
-    KernelArgsTy KernelArgs = {};
-    if (auto Err =
-            AMDGPUKernel.launchImpl(*this, /*NumThread=*/1u,
-                                    /*NumBlocks=*/1ul, KernelArgs,
-                                    KernelLaunchParamsTy{}, AsyncInfoWrapper))
-      return Err;
-
-    Error Err = Plugin::success();
-    AsyncInfoWrapper.finalize(Err);
-
-    return Err;
-  }
-
   /// Detect if current architecture is an APU.
   Error checkIfAPU() {
     // TODO: replace with ROCr API once it becomes available.

offload/plugins-nextgen/common/include/PluginInterface.h

@@ -722,18 +722,17 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
   Error synchronize(__tgt_async_info *AsyncInfo);
   virtual Error synchronizeImpl(__tgt_async_info &AsyncInfo) = 0;
 
-  /// Invokes any global constructors on the device if present and is required
-  /// by the target.
-  virtual Error callGlobalConstructors(GenericPluginTy &Plugin,
-                                       DeviceImageTy &Image) {
-    return Error::success();
+  /// Call the ctor/dtor of image \p Image, if available.
+  Error callGlobalCtorDtor(DeviceImageTy &Image, bool IsCtor);
+
+  /// Return the name of the global constructors on the device.
+  virtual Expected<StringRef> getGlobalConstructorName(DeviceImageTy &Image) {
+    return "";
   }
 
-  /// Invokes any global destructors on the device if present and is required
-  /// by the target.
-  virtual Error callGlobalDestructors(GenericPluginTy &Plugin,
-                                      DeviceImageTy &Image) {
-    return Error::success();
+  /// Return the name of the global destructors on the device.
+  virtual Expected<StringRef> getGlobalDestructorName(DeviceImageTy &Image) {
+    return "";
   }
 
   /// Query for the completion of the pending operations on the __tgt_async_info
@@ -928,8 +927,12 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
   bool useAutoZeroCopy();
   virtual bool useAutoZeroCopyImpl() { return false; }
 
-  /// Allocate and construct a kernel object.
-  virtual Expected<GenericKernelTy &> constructKernel(const char *Name) = 0;
+  /// Retrieve the kernel with name \p Name from image \p Image (or any image if
+  /// \p Image is null) and return it. If \p Optional is true, the function
+  /// returns success if there is no kernel with the given name.
+  Expected<GenericKernelTy *> getKernel(llvm::StringRef Name,
+                                        DeviceImageTy *Image = nullptr,
+                                        bool Optional = false);
 
   /// Reference to the underlying plugin that created this device.
   GenericPluginTy &Plugin;
@@ -947,6 +950,10 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
       UInt32Envar("OFFLOAD_TRACK_NUM_KERNEL_LAUNCH_TRACES", 0);
 
 private:
+  /// Allocate and construct a kernel object (users should use getKernel).
+  virtual Expected<GenericKernelTy &>
+  constructKernelImpl(llvm::StringRef Name) = 0;
+
   /// Get and set the stack size and heap size for the device. If not used, the
   /// plugin can implement the setters as no-op and setting the output
   /// value to zero for the getters.
@@ -1046,6 +1053,8 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
 private:
   DeviceMemoryPoolTy DeviceMemoryPool = {nullptr, 0};
   DeviceMemoryPoolTrackingTy DeviceMemoryPoolTracking = {0, 0, ~0U, 0};
+
+  DenseMap<StringRef, GenericKernelTy *> KernelMap;
 };
 
 /// Class implementing common functionalities of offload plugins. Each plugin

offload/plugins-nextgen/common/src/PluginInterface.cpp

@@ -809,7 +809,7 @@ Error GenericDeviceTy::init(GenericPluginTy &Plugin) {
 
 Error GenericDeviceTy::deinit(GenericPluginTy &Plugin) {
   for (DeviceImageTy *Image : LoadedImages)
-    if (auto Err = callGlobalDestructors(Plugin, *Image))
+    if (auto Err = callGlobalCtorDtor(*Image, /*Ctor*/ false))
       return Err;
 
   if (OMPX_DebugKind.get() & uint32_t(DeviceDebugKind::AllocationTracker)) {
@@ -866,6 +866,37 @@ Error GenericDeviceTy::deinit(GenericPluginTy &Plugin) {
 
   return deinitImpl();
 }
+
+Error GenericDeviceTy::callGlobalCtorDtor(DeviceImageTy &Image, bool IsCtor) {
+  auto NameOrErr =
+      IsCtor ? getGlobalConstructorName(Image) : getGlobalDestructorName(Image);
+  if (auto Err = NameOrErr.takeError())
+    return Err;
+  // No error but no name, that means there is no ctor/dtor.
+  if (NameOrErr->empty())
+    return Plugin::success();
+
+  auto KernelOrErr = getKernel(*NameOrErr, &Image, /*Optional=*/true);
+  if (auto Err = KernelOrErr.takeError())
+    return Err;
+
+  if (GenericKernelTy *Kernel = *KernelOrErr) {
+    KernelArgsTy KernelArgs;
+    KernelArgs.NumTeams[0] = KernelArgs.ThreadLimit[0] = 1;
+    AsyncInfoWrapperTy AsyncInfoWrapper(*this, nullptr);
+    if (auto Err = Kernel->launch(*this, /*ArgPtrs=*/nullptr,
+                                  /*ArgOffsets=*/nullptr, KernelArgs,
+                                  AsyncInfoWrapper))
+      return Err;
+
+    Error Err = Plugin::success();
+    AsyncInfoWrapper.finalize(Err);
+    return Err;
+  }
+
+  return Plugin::success();
+}
+
 Expected<DeviceImageTy *>
 GenericDeviceTy::loadBinary(GenericPluginTy &Plugin,
                             const __tgt_device_image *InputTgtImage) {
@@ -927,8 +958,8 @@ GenericDeviceTy::loadBinary(GenericPluginTy &Plugin,
 #endif
 
   // Call any global constructors present on the device.
-  if (auto Err = callGlobalConstructors(Plugin, *Image))
-    return std::move(Err);
+  if (auto Err = callGlobalCtorDtor(*Image, /*Ctor*/ true))
+    return Err;
 
   // Return the pointer to the table of entries.
   return Image;
@@ -1533,6 +1564,66 @@ Error GenericDeviceTy::printInfo() {
   return Plugin::success();
 }
 
+Expected<GenericKernelTy *> GenericDeviceTy::getKernel(llvm::StringRef Name,
+                                                       DeviceImageTy *ImagePtr,
+                                                       bool Optional) {
+  bool KernelFound = false;
+  GenericKernelTy *&KernelPtr = KernelMap[Name];
+  if (!KernelPtr) {
+    GenericGlobalHandlerTy &GHandler = Plugin.getGlobalHandler();
+
+    auto CheckImage = [&](DeviceImageTy &Image) -> GenericKernelTy * {
+      if (!GHandler.isSymbolInImage(*this, Image, Name))
+        return nullptr;
+
+      auto KernelOrErr = constructKernelImpl(Name);
+      if (Error Err = KernelOrErr.takeError()) {
+        [[maybe_unused]] std::string ErrStr = toString(std::move(Err));
+        DP("Failed to construct kernel ('%s'): %s", Name.data(),
+           ErrStr.c_str());
+        return nullptr;
+      }
+
+      GenericKernelTy &Kernel = *KernelOrErr;
+      if (auto Err = Kernel.init(*this, Image)) {
+        [[maybe_unused]] std::string ErrStr = toString(std::move(Err));
+        DP("Failed to initialize kernel ('%s'): %s", Name.data(),
+           ErrStr.c_str());
+        return nullptr;
+      }
+
+      return &Kernel;
+    };
+
+    if (ImagePtr) {
+      KernelPtr = CheckImage(*ImagePtr);
+    } else {
+      for (DeviceImageTy *Image : LoadedImages) {
+        KernelPtr = CheckImage(*Image);
+        if (KernelPtr)
+          break;
+      }
+    }
+  }
+
+  // If we didn't find the kernel and it was optional, we do not emit an error.
+  if (!KernelPtr && !KernelFound && Optional)
+    return nullptr;
+  // If we didn't find the kernel and it was not optional, we will emit an
+  // error.
+  if (!KernelPtr && !KernelFound)
+    return Plugin::error("Kernel '%s' not found, searched %zu images",
+                         Name.data(),
+                         ImagePtr ? size_t(1) : LoadedImages.size());
+  // If we found the kernel but couldn't initialize it, we will emit an error.
+  if (!KernelPtr)
+    return Plugin::error(
+        "Kernel '%s' failed to initialize, searched %zu images", Name.data(),
+        ImagePtr ? size_t(1) : LoadedImages.size());
+  // Found the kernel and initialized it.
+  return KernelPtr;
+}
+
 Error GenericDeviceTy::createEvent(void **EventPtrStorage) {
   return createEventImpl(EventPtrStorage);
 }
@@ -2147,20 +2238,14 @@ int32_t GenericPluginTy::get_function(__tgt_device_binary Binary,
 
   GenericDeviceTy &Device = Image.getDevice();
 
-  auto KernelOrErr = Device.constructKernel(Name);
+  auto KernelOrErr = Device.getKernel(Name, &Image);
   if (Error Err = KernelOrErr.takeError()) {
     REPORT("Failure to look up kernel: %s\n", toString(std::move(Err)).data());
     return OFFLOAD_FAIL;
   }
 
-  GenericKernelTy &Kernel = *KernelOrErr;
-  if (auto Err = Kernel.init(Device, Image)) {
-    REPORT("Failure to init kernel: %s\n", toString(std::move(Err)).data());
-    return OFFLOAD_FAIL;
-  }
-
   // Note that this is not the kernel's device address.
-  *KernelPtr = &Kernel;
+  *KernelPtr = *KernelOrErr;
   return OFFLOAD_SUCCESS;
 }