Move Shader JIT Multithreading to a Separate Branch

src/video_core/shader/shader_jit.cpp

@@ -1,4 +1,4 @@
-// Copyright Citra Emulator Project / Azahar Emulator Project
+// Copyright 2016 Citra Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
@@ -16,79 +16,11 @@
 #if CITRA_ARCH(x86_64)
 #include "video_core/shader/shader_jit_x64_compiler.h"
 #endif
-#include <future>
 
 namespace Pica::Shader {
 
-JitEngine::JitEngine() {
-    stub_shader = std::make_unique<JitShader>();
-    // Optionally, compile a minimal stub shader here if needed
-    StartThreadPool(std::thread::hardware_concurrency());
-}
-
-JitEngine::~JitEngine() {
-    StopThreadPool();
-}
-
-void JitEngine::StartThreadPool(size_t num_threads) {
-    stop_threads = false;
-    for (size_t i = 0; i < num_threads; ++i) {
-        thread_pool.emplace_back([this]() { ThreadWorker(); });
-    }
-}
-
-void JitEngine::StopThreadPool() {
-    {
-        std::lock_guard<std::mutex> lock(queue_mutex);
-        stop_threads = true;
-    }
-    queue_cv.notify_all();
-    for (auto& t : thread_pool) {
-        if (t.joinable())
-            t.join();
-    }
-    thread_pool.clear();
-}
-
-void JitEngine::ThreadWorker() {
-    while (true) {
-        std::function<void()> job;
-        {
-            std::unique_lock<std::mutex> lock(queue_mutex);
-            queue_cv.wait(lock, [this]() { return stop_threads || !compile_queue.empty(); });
-            if (stop_threads && compile_queue.empty())
-                return;
-            job = std::move(compile_queue.front());
-            compile_queue.pop();
-        }
-        job();
-    }
-}
-
-void JitEngine::EnqueueCompilation(u64 cache_key, ShaderSetup setup_copy) {
-    // WARNING: Copying ShaderSetup across threads may be unsafe if it contains raw pointers or
-    // non-trivial resources. Consider refactoring to only copy the necessary data for compilation.
-    auto promise = std::make_shared<std::promise<std::unique_ptr<JitShader>>>();
-    {
-        std::lock_guard<std::mutex> lock(queue_mutex);
-        compile_queue.emplace([this, cache_key, setup_copy, promise]() mutable {
-            auto shader = std::make_unique<JitShader>();
-            shader->Compile(&setup_copy.program_code, &setup_copy.swizzle_data);
-            {
-                std::lock_guard<std::mutex> lock2(cache_mutex);
-                if (cache.size() >= MAX_CACHE_SIZE) {
-                    EvictLRU();
-                }
-                promise->set_value(std::move(shader));
-                cache[cache_key] = promise->get_future().share();
-                lru_list.push_front(cache_key);
-            }
-        });
-        // Store the future in the cache immediately so SetupBatch can wait on it
-        cache[cache_key] = promise->get_future().share();
-    }
-    queue_cv.notify_one();
-}
+JitEngine::JitEngine() = default;
+JitEngine::~JitEngine() = default;
 
 void JitEngine::SetupBatch(ShaderSetup& setup, u32 entry_point) {
     ASSERT(entry_point < MAX_PROGRAM_CODE_LENGTH);
@@ -96,54 +28,23 @@ void JitEngine::SetupBatch(ShaderSetup& setup, u32 entry_point) {
 
     const u64 code_hash = setup.GetProgramCodeHash();
     const u64 swizzle_hash = setup.GetSwizzleDataHash();
+
     const u64 cache_key = Common::HashCombine(code_hash, swizzle_hash);
-
-    std::shared_future<std::unique_ptr<JitShader>> shader_future;
-    {
-        std::lock_guard<std::mutex> lock(cache_mutex);
-        auto iter = cache.find(cache_key);
-        if (iter != cache.end()) {
-            shader_future = iter->second;
-            UpdateLRU(cache_key);
-        } else {
-            // Compile synchronously and store the result
-            auto shader = std::make_unique<JitShader>();
-            shader->Compile(&setup.program_code, &setup.swizzle_data);
-            auto ready_future = std::make_shared<std::promise<std::unique_ptr<JitShader>>>();
-            ready_future->set_value(std::move(shader));
-            shader_future = ready_future->get_future().share();
-            cache[cache_key] = shader_future;
-            lru_list.push_front(cache_key);
-        }
+    auto iter = cache.find(cache_key);
+    if (iter != cache.end()) {
+        setup.cached_shader = iter->second.get();
+    } else {
+        auto shader = std::make_unique<JitShader>();
+        shader->Compile(&setup.program_code, &setup.swizzle_data);
+        setup.cached_shader = shader.get();
+        cache.emplace_hint(iter, cache_key, std::move(shader));
     }
-    // Wait for the shader to be ready (if compiling in background)
-    setup.cached_shader = shader_future.get().get();
-}
-
-void JitEngine::EvictLRU() {
-    if (lru_list.empty()) {
-        return;
-    }
-    const u64 key = lru_list.back();
-    lru_list.pop_back();
-    cache.erase(key);
-}
-
-void JitEngine::UpdateLRU(u64 key) {
-    auto it = std::find(lru_list.begin(), lru_list.end(), key);
-    if (it != lru_list.end()) {
-        lru_list.erase(it);
-    }
-    lru_list.push_front(key);
 }
 
 MICROPROFILE_DECLARE(GPU_Shader);
 
 void JitEngine::Run(const ShaderSetup& setup, ShaderUnit& state) const {
-    // Null check: skip draw if shader is not ready
-    if (!setup.cached_shader) {
-        return;
-    }
+    ASSERT(setup.cached_shader != nullptr);
 
     MICROPROFILE_SCOPE(GPU_Shader);
 

src/video_core/shader/shader_jit.h

@@ -1,4 +1,4 @@
-// Copyright Citra Emulator Project / Azahar Emulator Project
+// Copyright 2016 Citra Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
@@ -7,14 +7,8 @@
 #include "common/arch.h"
 #if CITRA_ARCH(x86_64) || CITRA_ARCH(arm64)
 
-#include <functional>
-#include <future>
-#include <list>
 #include <memory>
-#include <mutex>
-#include <thread>
 #include <unordered_map>
-#include <queue>
 #include "common/common_types.h"
 #include "video_core/shader/shader.h"
 
@@ -31,25 +25,7 @@ public:
     void Run(const ShaderSetup& setup, ShaderUnit& state) const override;
 
 private:
-    static constexpr size_t MAX_CACHE_SIZE = 1000; // Maximum number of shaders to cache
-    std::unordered_map<u64, std::shared_future<std::unique_ptr<JitShader>>> cache;
-    std::list<u64> lru_list; // Track LRU order of shaders
-    mutable std::mutex cache_mutex;
-
-    // Parallel compilation support
-    std::vector<std::thread> thread_pool;
-    std::queue<std::function<void()>> compile_queue;
-    std::mutex queue_mutex;
-    std::condition_variable queue_cv;
-    bool stop_threads = false;
-    std::unique_ptr<JitShader> stub_shader;
-
-    void EvictLRU();
-    void UpdateLRU(u64 key);
-    void ThreadWorker();
-    void EnqueueCompilation(u64 cache_key, ShaderSetup setup_copy);
-    void StartThreadPool(size_t num_threads);
-    void StopThreadPool();
+    std::unordered_map<u64, std::unique_ptr<JitShader>> cache;
 };
 
 } // namespace Pica::Shader