context_mtl.mm

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#include "impeller/renderer/backend/metal/context_mtl.h"
 
#include <Foundation/Foundation.h>
#include <memory>
 
#include "flutter/fml/concurrent_message_loop.h"
#include "flutter/fml/file.h"
#include "flutter/fml/logging.h"
#include "flutter/fml/paths.h"
#include "flutter/fml/synchronization/sync_switch.h"
#include "impeller/core/formats.h"
#include "impeller/core/sampler_descriptor.h"
#include "impeller/renderer/backend/metal/gpu_tracer_mtl.h"
#include "impeller/renderer/backend/metal/sampler_library_mtl.h"
#include "impeller/renderer/capabilities.h"
 
namespace impeller {
 
static bool DeviceSupportsFramebufferFetch(id<MTLDevice> device) {
  // The iOS simulator lies about supporting framebuffer fetch.
#if FML_OS_IOS_SIMULATOR
  return false;
#else  // FML_OS_IOS_SIMULATOR
 
  if (@available(macOS 10.15, iOS 13, tvOS 13, *)) {
    return [device supportsFamily:MTLGPUFamilyApple2];
  }
  // According to
  // https://developer.apple.com/metal/Metal-Feature-Set-Tables.pdf , Apple2
  // corresponds to iOS GPU family 2, which supports A8 devices.
#if FML_OS_IOS
  return [device supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily2_v1];
#else
  return false;
#endif  // FML_OS_IOS
#endif  // FML_OS_IOS_SIMULATOR
}
 
static bool DeviceSupportsComputeSubgroups(id<MTLDevice> device) {
  bool supports_subgroups = false;
  // Refer to the "SIMD-scoped reduction operations" feature in the table
  // below: https://developer.apple.com/metal/Metal-Feature-Set-Tables.pdf
  if (@available(ios 13.0, tvos 13.0, macos 10.15, *)) {
    supports_subgroups = [device supportsFamily:MTLGPUFamilyApple7] ||
                         [device supportsFamily:MTLGPUFamilyMac2];
  }
  return supports_subgroups;
}
 
static std::unique_ptr<Capabilities> InferMetalCapabilities(
    id<MTLDevice> device,
    PixelFormat color_format) {
  return CapabilitiesBuilder()
      .SetSupportsOffscreenMSAA(true)
      .SetSupportsSSBO(true)
      .SetSupportsBufferToTextureBlits(true)
      .SetSupportsTextureToTextureBlits(true)
      .SetSupportsDecalSamplerAddressMode(true)
      .SetSupportsFramebufferFetch(DeviceSupportsFramebufferFetch(device))
      .SetDefaultColorFormat(color_format)
      .SetDefaultStencilFormat(PixelFormat::kS8UInt)
      .SetDefaultDepthStencilFormat(PixelFormat::kD32FloatS8UInt)
      .SetSupportsCompute(true)
      .SetSupportsComputeSubgroups(DeviceSupportsComputeSubgroups(device))
      .SetSupportsReadFromResolve(true)
      .SetSupportsDeviceTransientTextures(true)
      .Build();
}
 
ContextMTL::ContextMTL(
    id<MTLDevice> device,
    id<MTLCommandQueue> command_queue,
    NSArray<id<MTLLibrary>>* shader_libraries,
    std::shared_ptr<const fml::SyncSwitch> is_gpu_disabled_sync_switch)
    : device_(device),
      command_queue_(command_queue),
      is_gpu_disabled_sync_switch_(std::move(is_gpu_disabled_sync_switch)) {
  // Validate device.
  if (!device_) {
    VALIDATION_LOG << "Could not set up valid Metal device.";
    return;
  }
 
  sync_switch_observer_.reset(new SyncSwitchObserver(*this));
  is_gpu_disabled_sync_switch_->AddObserver(sync_switch_observer_.get());
 
  // Worker task runner.
  {
    raster_message_loop_ = fml::ConcurrentMessageLoop::Create(
        std::min(4u, std::thread::hardware_concurrency()));
    raster_message_loop_->PostTaskToAllWorkers([]() {
      // See https://github.com/flutter/flutter/issues/65752
      // Intentionally opt out of QoS for raster task workloads.
      [[NSThread currentThread] setThreadPriority:1.0];
      sched_param param;
      int policy;
      pthread_t thread = pthread_self();
      if (!pthread_getschedparam(thread, &policy, &param)) {
        param.sched_priority = 50;
        pthread_setschedparam(thread, policy, &param);
      }
    });
  }
 
  // Setup the shader library.
  {
    if (shader_libraries == nil) {
      VALIDATION_LOG << "Shader libraries were null.";
      return;
    }
 
    // std::make_shared disallowed because of private friend ctor.
    auto library = std::shared_ptr<ShaderLibraryMTL>(
        new ShaderLibraryMTL(shader_libraries));
    if (!library->IsValid()) {
      VALIDATION_LOG << "Could not create valid Metal shader library.";
      return;
    }
    shader_library_ = std::move(library);
  }
 
  // Setup the pipeline library.
  {
    pipeline_library_ =
        std::shared_ptr<PipelineLibraryMTL>(new PipelineLibraryMTL(device_));
  }
 
  // Setup the sampler library.
  {
    sampler_library_ =
        std::shared_ptr<SamplerLibraryMTL>(new SamplerLibraryMTL(device_));
  }
 
  // Setup the resource allocator.
  {
    resource_allocator_ = std::shared_ptr<AllocatorMTL>(
        new AllocatorMTL(device_, "Impeller Permanents Allocator"));
    if (!resource_allocator_) {
      VALIDATION_LOG << "Could not set up the resource allocator.";
      return;
    }
  }
 
  device_capabilities_ =
      InferMetalCapabilities(device_, PixelFormat::kB8G8R8A8UNormInt);
#ifdef IMPELLER_DEBUG
  gpu_tracer_ = std::make_shared<GPUTracerMTL>();
#endif  // IMPELLER_DEBUG
  is_valid_ = true;
}
 
static NSArray<id<MTLLibrary>>* MTLShaderLibraryFromFilePaths(
    id<MTLDevice> device,
    const std::vector<std::string>& libraries_paths) {
  NSMutableArray<id<MTLLibrary>>* found_libraries = [NSMutableArray array];
  for (const auto& library_path : libraries_paths) {
    if (!fml::IsFile(library_path)) {
      VALIDATION_LOG << "Shader library does not exist at path '"
                     << library_path << "'";
      return nil;
    }
    NSError* shader_library_error = nil;
    auto library = [device newLibraryWithFile:@(library_path.c_str())
                                        error:&shader_library_error];
    if (!library) {
      FML_LOG(ERROR) << "Could not create shader library: "
                     << shader_library_error.localizedDescription.UTF8String;
      return nil;
    }
    [found_libraries addObject:library];
  }
  return found_libraries;
}
 
static NSArray<id<MTLLibrary>>* MTLShaderLibraryFromFileData(
    id<MTLDevice> device,
    const std::vector<std::shared_ptr<fml::Mapping>>& libraries_data,
    const std::string& label) {
  NSMutableArray<id<MTLLibrary>>* found_libraries = [NSMutableArray array];
  for (const auto& library_data : libraries_data) {
    if (library_data == nullptr) {
      FML_LOG(ERROR) << "Shader library data was null.";
      return nil;
    }
 
    __block auto data = library_data;
 
    auto dispatch_data =
        ::dispatch_data_create(library_data->GetMapping(),  // buffer
                               library_data->GetSize(),     // size
                               dispatch_get_main_queue(),   // queue
                               ^() {
                                 // We just need a reference.
                                 data.reset();
                               }  // destructor
        );
    if (!dispatch_data) {
      FML_LOG(ERROR) << "Could not wrap shader data in dispatch data.";
      return nil;
    }
 
    NSError* shader_library_error = nil;
    auto library = [device newLibraryWithData:dispatch_data
                                        error:&shader_library_error];
    if (!library) {
      FML_LOG(ERROR) << "Could not create shader library: "
                     << shader_library_error.localizedDescription.UTF8String;
      return nil;
    }
    if (!label.empty()) {
      library.label = @(label.c_str());
    }
    [found_libraries addObject:library];
  }
  return found_libraries;
}
 
static id<MTLDevice> CreateMetalDevice() {
  return ::MTLCreateSystemDefaultDevice();
}
 
static id<MTLCommandQueue> CreateMetalCommandQueue(id<MTLDevice> device) {
  auto command_queue = device.newCommandQueue;
  if (!command_queue) {
    VALIDATION_LOG << "Could not set up the command queue.";
    return nullptr;
  }
  command_queue.label = @"Impeller Command Queue";
  return command_queue;
}
 
std::shared_ptr<ContextMTL> ContextMTL::Create(
    const std::vector<std::string>& shader_library_paths,
    std::shared_ptr<const fml::SyncSwitch> is_gpu_disabled_sync_switch) {
  auto device = CreateMetalDevice();
  auto command_queue = CreateMetalCommandQueue(device);
  if (!command_queue) {
    return nullptr;
  }
  auto context = std::shared_ptr<ContextMTL>(new ContextMTL(
      device, command_queue,
      MTLShaderLibraryFromFilePaths(device, shader_library_paths),
      std::move(is_gpu_disabled_sync_switch)));
  if (!context->IsValid()) {
    FML_LOG(ERROR) << "Could not create Metal context.";
    return nullptr;
  }
  return context;
}
 
std::shared_ptr<ContextMTL> ContextMTL::Create(
    const std::vector<std::shared_ptr<fml::Mapping>>& shader_libraries_data,
    std::shared_ptr<const fml::SyncSwitch> is_gpu_disabled_sync_switch,
    const std::string& library_label) {
  auto device = CreateMetalDevice();
  auto command_queue = CreateMetalCommandQueue(device);
  if (!command_queue) {
    return nullptr;
  }
  auto context = std::shared_ptr<ContextMTL>(
      new ContextMTL(device, command_queue,
                     MTLShaderLibraryFromFileData(device, shader_libraries_data,
                                                  library_label),
                     std::move(is_gpu_disabled_sync_switch)));
  if (!context->IsValid()) {
    FML_LOG(ERROR) << "Could not create Metal context.";
    return nullptr;
  }
  return context;
}
 
std::shared_ptr<ContextMTL> ContextMTL::Create(
    id<MTLDevice> device,
    id<MTLCommandQueue> command_queue,
    const std::vector<std::shared_ptr<fml::Mapping>>& shader_libraries_data,
    std::shared_ptr<const fml::SyncSwitch> is_gpu_disabled_sync_switch,
    const std::string& library_label) {
  auto context = std::shared_ptr<ContextMTL>(
      new ContextMTL(device, command_queue,
                     MTLShaderLibraryFromFileData(device, shader_libraries_data,
                                                  library_label),
                     std::move(is_gpu_disabled_sync_switch)));
  if (!context->IsValid()) {
    FML_LOG(ERROR) << "Could not create Metal context.";
    return nullptr;
  }
  return context;
}
 
ContextMTL::~ContextMTL() {
  is_gpu_disabled_sync_switch_->RemoveObserver(sync_switch_observer_.get());
}
 
Context::BackendType ContextMTL::GetBackendType() const {
  return Context::BackendType::kMetal;
}
 
// |Context|
std::string ContextMTL::DescribeGpuModel() const {
  return std::string([[device_ name] UTF8String]);
}
 
// |Context|
bool ContextMTL::IsValid() const {
  return is_valid_;
}
 
// |Context|
std::shared_ptr<ShaderLibrary> ContextMTL::GetShaderLibrary() const {
  return shader_library_;
}
 
// |Context|
std::shared_ptr<PipelineLibrary> ContextMTL::GetPipelineLibrary() const {
  return pipeline_library_;
}
 
// |Context|
std::shared_ptr<SamplerLibrary> ContextMTL::GetSamplerLibrary() const {
  return sampler_library_;
}
 
// |Context|
std::shared_ptr<CommandBuffer> ContextMTL::CreateCommandBuffer() const {
  return CreateCommandBufferInQueue(command_queue_);
}
 
// |Context|
void ContextMTL::Shutdown() {
  raster_message_loop_.reset();
}
 
#ifdef IMPELLER_DEBUG
std::shared_ptr<GPUTracerMTL> ContextMTL::GetGPUTracer() const {
  return gpu_tracer_;
}
#endif  // IMPELLER_DEBUG
 
const std::shared_ptr<fml::ConcurrentTaskRunner>
ContextMTL::GetWorkerTaskRunner() const {
  return raster_message_loop_->GetTaskRunner();
}
 
std::shared_ptr<const fml::SyncSwitch> ContextMTL::GetIsGpuDisabledSyncSwitch()
    const {
  return is_gpu_disabled_sync_switch_;
}
 
std::shared_ptr<CommandBuffer> ContextMTL::CreateCommandBufferInQueue(
    id<MTLCommandQueue> queue) const {
  if (!IsValid()) {
    return nullptr;
  }
 
  auto buffer = std::shared_ptr<CommandBufferMTL>(
      new CommandBufferMTL(weak_from_this(), queue));
  if (!buffer->IsValid()) {
    return nullptr;
  }
  return buffer;
}
 
std::shared_ptr<Allocator> ContextMTL::GetResourceAllocator() const {
  return resource_allocator_;
}
 
id<MTLDevice> ContextMTL::GetMTLDevice() const {
  return device_;
}
 
const std::shared_ptr<const Capabilities>& ContextMTL::GetCapabilities() const {
  return device_capabilities_;
}
 
void ContextMTL::SetCapabilities(
    const std::shared_ptr<const Capabilities>& capabilities) {
  device_capabilities_ = capabilities;
}
 
// |Context|
bool ContextMTL::UpdateOffscreenLayerPixelFormat(PixelFormat format) {
  device_capabilities_ = InferMetalCapabilities(device_, format);
  return true;
}
 
id<MTLCommandBuffer> ContextMTL::CreateMTLCommandBuffer(
    const std::string& label) const {
  auto buffer = [command_queue_ commandBuffer];
  if (!label.empty()) {
    [buffer setLabel:@(label.data())];
  }
  return buffer;
}
 
void ContextMTL::StoreTaskForGPU(const std::function<void()>& task) {
  tasks_awaiting_gpu_.emplace_back(task);
  while (tasks_awaiting_gpu_.size() > kMaxTasksAwaitingGPU) {
    tasks_awaiting_gpu_.front()();
    tasks_awaiting_gpu_.pop_front();
  }
}
 
void ContextMTL::FlushTasksAwaitingGPU() {
  for (const auto& task : tasks_awaiting_gpu_) {
    task();
  }
  tasks_awaiting_gpu_.clear();
}
 
ContextMTL::SyncSwitchObserver::SyncSwitchObserver(ContextMTL& parent)
    : parent_(parent) {}
 
void ContextMTL::SyncSwitchObserver::OnSyncSwitchUpdate(bool new_is_disabled) {
  if (!new_is_disabled) {
    parent_.FlushTasksAwaitingGPU();
  }
}
 
}  // namespace impeller