ARM_Interface: Cache the JITs instead of deleting/recreating.

This was a bug inherited from citra which was fixed by then at some 
time. This commit corrects such bug and ensures JITs are correctly 
recycled.

src/core/arm/dynarmic/arm_dynarmic.cpp

@@ -132,7 +132,7 @@ public:
     u64 tpidr_el0 = 0;
 };
 
-std::unique_ptr<Dynarmic::A64::Jit> ARM_Dynarmic::MakeJit(Common::PageTable& page_table,
+std::shared_ptr<Dynarmic::A64::Jit> ARM_Dynarmic::MakeJit(Common::PageTable& page_table,
                                                           std::size_t address_space_bits) const {
     Dynarmic::A64::UserConfig config;
 
@@ -159,7 +159,7 @@ std::unique_ptr<Dynarmic::A64::Jit> ARM_Dynarmic::MakeJit(Common::PageTable& pag
     // Unpredictable instructions
     config.define_unpredictable_behaviour = true;
 
-    return std::make_unique<Dynarmic::A64::Jit>(config);
+    return std::make_shared<Dynarmic::A64::Jit>(config);
 }
 
 MICROPROFILE_DEFINE(ARM_Jit_Dynarmic, "ARM JIT", "Dynarmic", MP_RGB(255, 64, 64));
@@ -267,7 +267,14 @@ void ARM_Dynarmic::ClearExclusiveState() {
 
 void ARM_Dynarmic::PageTableChanged(Common::PageTable& page_table,
                                     std::size_t new_address_space_size_in_bits) {
+    auto key = std::make_pair(&page_table, new_address_space_size_in_bits);
+    auto iter = jit_cache.find(key);
+    if (iter != jit_cache.end()) {
+        jit = iter->second;
+        return;
+    }
     jit = MakeJit(page_table, new_address_space_size_in_bits);
+    jit_cache.emplace(key, jit);
 }
 
 DynarmicExclusiveMonitor::DynarmicExclusiveMonitor(Memory::Memory& memory_, std::size_t core_count)

src/core/arm/dynarmic/arm_dynarmic.h

@@ -5,9 +5,12 @@
 #pragma once
 
 #include <memory>
+#include <unordered_map>
+
 #include <dynarmic/A64/a64.h>
 #include <dynarmic/A64/exclusive_monitor.h>
 #include "common/common_types.h"
+#include "common/hash.h"
 #include "core/arm/arm_interface.h"
 #include "core/arm/exclusive_monitor.h"
 #include "core/arm/unicorn/arm_unicorn.h"
@@ -22,6 +25,10 @@ class ARM_Dynarmic_Callbacks;
 class DynarmicExclusiveMonitor;
 class System;
 
+using JitCacheKey = std::pair<Common::PageTable*, std::size_t>;
+using JitCacheType =
+    std::unordered_map<JitCacheKey, std::shared_ptr<Dynarmic::A64::Jit>, Common::PairHash>;
+
 class ARM_Dynarmic final : public ARM_Interface {
 public:
     ARM_Dynarmic(System& system, ExclusiveMonitor& exclusive_monitor, std::size_t core_index);
@@ -53,12 +60,13 @@ public:
                           std::size_t new_address_space_size_in_bits) override;
 
 private:
-    std::unique_ptr<Dynarmic::A64::Jit> MakeJit(Common::PageTable& page_table,
+    std::shared_ptr<Dynarmic::A64::Jit> MakeJit(Common::PageTable& page_table,
                                                 std::size_t address_space_bits) const;
 
     friend class ARM_Dynarmic_Callbacks;
     std::unique_ptr<ARM_Dynarmic_Callbacks> cb;
-    std::unique_ptr<Dynarmic::A64::Jit> jit;
+    JitCacheType jit_cache;
+    std::shared_ptr<Dynarmic::A64::Jit> jit;
     ARM_Unicorn inner_unicorn;
 
     std::size_t core_index;