From 2779da323b3364da9464c8653b1991d7419b9527 Mon Sep 17 00:00:00 2001
From: jbm11208 <81182113+jbm11208@users.noreply.github.com>
Date: Sun, 11 May 2025 23:51:26 -0400
Subject: [PATCH] Implement LRU-based shader cache eviction and size limit in
 JIT engine

---
 src/video_core/shader/shader_jit.cpp | 27 +++++++++++++++++++++++++--
 src/video_core/shader/shader_jit.h   | 10 +++++++++-
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/src/video_core/shader/shader_jit.cpp b/src/video_core/shader/shader_jit.cpp
index 644586226..3f34e568d 100644
--- a/src/video_core/shader/shader_jit.cpp
+++ b/src/video_core/shader/shader_jit.cpp
@@ -1,4 +1,4 @@
-// Copyright 2016 Citra Emulator Project
+// Copyright Citra Emulator Project / Azahar Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
@@ -28,19 +28,42 @@ 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::lock_guard<std::mutex> lock(cache_mutex);
     auto iter = cache.find(cache_key);
     if (iter != cache.end()) {
         setup.cached_shader = iter->second.get();
+        UpdateLRU(cache_key);
     } else {
+        if (cache.size() >= MAX_CACHE_SIZE) {
+            EvictLRU();
+        }
         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));
+        lru_list.push_front(cache_key);
     }
 }
 
+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 {
diff --git a/src/video_core/shader/shader_jit.h b/src/video_core/shader/shader_jit.h
index 2f3e77b02..912fc5fe2 100644
--- a/src/video_core/shader/shader_jit.h
+++ b/src/video_core/shader/shader_jit.h
@@ -1,4 +1,4 @@
-// Copyright 2016 Citra Emulator Project
+// Copyright Citra Emulator Project / Azahar Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
@@ -7,7 +7,9 @@
 #include "common/arch.h"
 #if CITRA_ARCH(x86_64) || CITRA_ARCH(arm64)
 
+#include <list>
 #include <memory>
+#include <mutex>
 #include <unordered_map>
 #include "common/common_types.h"
 #include "video_core/shader/shader.h"
@@ -25,7 +27,13 @@ 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::unique_ptr<JitShader>> cache;
+    std::list<u64> lru_list; // Track LRU order of shaders
+    mutable std::mutex cache_mutex;
+
+    void EvictLRU();
+    void UpdateLRU(u64 key);
 };
 
 } // namespace Pica::Shader