8 files changed, 484 insertions, 19 deletions

diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 43ae8a9e7..850ce8006 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -98,6 +98,7 @@ add_library(common STATIC
     microprofile.h
     microprofileui.h
     misc.cpp
+    multi_level_queue.h
     page_table.cpp
     page_table.h
     param_package.cpp
diff --git a/src/common/bit_util.h b/src/common/bit_util.h
index 1eea17ba1..a4f9ed4aa 100644
--- a/src/common/bit_util.h
+++ b/src/common/bit_util.h
@@ -58,4 +58,43 @@ inline u64 CountLeadingZeroes64(u64 value) {
     return __builtin_clzll(value);
 }
 #endif
+
+#ifdef _MSC_VER
+inline u32 CountTrailingZeroes32(u32 value) {
+    unsigned long trailing_zero = 0;
+
+    if (_BitScanForward(&trailing_zero, value) != 0) {
+        return trailing_zero;
+    }
+
+    return 32;
+}
+
+inline u64 CountTrailingZeroes64(u64 value) {
+    unsigned long trailing_zero = 0;
+
+    if (_BitScanForward64(&trailing_zero, value) != 0) {
+        return trailing_zero;
+    }
+
+    return 64;
+}
+#else
+inline u32 CountTrailingZeroes32(u32 value) {
+    if (value == 0) {
+        return 32;
+    }
+
+    return __builtin_ctz(value);
+}
+
+inline u64 CountTrailingZeroes64(u64 value) {
+    if (value == 0) {
+        return 64;
+    }
+
+    return __builtin_ctzll(value);
+}
+#endif
+
 } // namespace Common
diff --git a/src/common/multi_level_queue.h b/src/common/multi_level_queue.h
new file mode 100644
index 000000000..2b61b91e0
--- /dev/null
+++ b/src/common/multi_level_queue.h
@@ -0,0 +1,337 @@
+// Copyright 2019 TuxSH
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <iterator>
+#include <list>
+#include <utility>
+
+#include "common/bit_util.h"
+#include "common/common_types.h"
+
+namespace Common {
+
+/**
+ * A MultiLevelQueue is a type of priority queue which has the following characteristics:
+ * - iteratable through each of its elements.
+ * - back can be obtained.
+ * - O(1) add, lookup (both front and back)
+ * - discrete priorities and a max of 64 priorities (limited domain)
+ * This type of priority queue is normaly used for managing threads within an scheduler
+ */
+template <typename T, std::size_t Depth>
+class MultiLevelQueue {
+public:
+    using value_type = T;
+    using reference = value_type&;
+    using const_reference = const value_type&;
+    using pointer = value_type*;
+    using const_pointer = const value_type*;
+
+    using difference_type = typename std::pointer_traits<pointer>::difference_type;
+    using size_type = std::size_t;
+
+    template <bool is_constant>
+    class iterator_impl {
+    public:
+        using iterator_category = std::bidirectional_iterator_tag;
+        using value_type = T;
+        using pointer = std::conditional_t<is_constant, T*, const T*>;
+        using reference = std::conditional_t<is_constant, const T&, T&>;
+        using difference_type = typename std::pointer_traits<pointer>::difference_type;
+
+        friend bool operator==(const iterator_impl& lhs, const iterator_impl& rhs) {
+            if (lhs.IsEnd() && rhs.IsEnd())
+                return true;
+            return std::tie(lhs.current_priority, lhs.it) == std::tie(rhs.current_priority, rhs.it);
+        }
+
+        friend bool operator!=(const iterator_impl& lhs, const iterator_impl& rhs) {
+            return !operator==(lhs, rhs);
+        }
+
+        reference operator*() const {
+            return *it;
+        }
+
+        pointer operator->() const {
+            return it.operator->();
+        }
+
+        iterator_impl& operator++() {
+            if (IsEnd()) {
+                return *this;
+            }
+
+            ++it;
+
+            if (it == GetEndItForPrio()) {
+                u64 prios = mlq.used_priorities;
+                prios &= ~((1ULL << (current_priority + 1)) - 1);
+                if (prios == 0) {
+                    current_priority = mlq.depth();
+                } else {
+                    current_priority = CountTrailingZeroes64(prios);
+                    it = GetBeginItForPrio();
+                }
+            }
+            return *this;
+        }
+
+        iterator_impl& operator--() {
+            if (IsEnd()) {
+                if (mlq.used_priorities != 0) {
+                    current_priority = 63 - CountLeadingZeroes64(mlq.used_priorities);
+                    it = GetEndItForPrio();
+                    --it;
+                }
+            } else if (it == GetBeginItForPrio()) {
+                u64 prios = mlq.used_priorities;
+                prios &= (1ULL << current_priority) - 1;
+                if (prios != 0) {
+                    current_priority = CountTrailingZeroes64(prios);
+                    it = GetEndItForPrio();
+                    --it;
+                }
+            } else {
+                --it;
+            }
+            return *this;
+        }
+
+        iterator_impl operator++(int) {
+            const iterator_impl v{*this};
+            ++(*this);
+            return v;
+        }
+
+        iterator_impl operator--(int) {
+            const iterator_impl v{*this};
+            --(*this);
+            return v;
+        }
+
+        // allow implicit const->non-const
+        iterator_impl(const iterator_impl<false>& other)
+            : mlq(other.mlq), it(other.it), current_priority(other.current_priority) {}
+
+        iterator_impl(const iterator_impl<true>& other)
+            : mlq(other.mlq), it(other.it), current_priority(other.current_priority) {}
+
+        iterator_impl& operator=(const iterator_impl<false>& other) {
+            mlq = other.mlq;
+            it = other.it;
+            current_priority = other.current_priority;
+            return *this;
+        }
+
+        friend class iterator_impl<true>;
+        iterator_impl() = default;
+
+    private:
+        friend class MultiLevelQueue;
+        using container_ref =
+            std::conditional_t<is_constant, const MultiLevelQueue&, MultiLevelQueue&>;
+        using list_iterator = std::conditional_t<is_constant, typename std::list<T>::const_iterator,
+                                                 typename std::list<T>::iterator>;
+
+        explicit iterator_impl(container_ref mlq, list_iterator it, u32 current_priority)
+            : mlq(mlq), it(it), current_priority(current_priority) {}
+        explicit iterator_impl(container_ref mlq, u32 current_priority)
+            : mlq(mlq), it(), current_priority(current_priority) {}
+
+        bool IsEnd() const {
+            return current_priority == mlq.depth();
+        }
+
+        list_iterator GetBeginItForPrio() const {
+            return mlq.levels[current_priority].begin();
+        }
+
+        list_iterator GetEndItForPrio() const {
+            return mlq.levels[current_priority].end();
+        }
+
+        container_ref mlq;
+        list_iterator it;
+        u32 current_priority;
+    };
+
+    using iterator = iterator_impl<false>;
+    using const_iterator = iterator_impl<true>;
+
+    void add(const T& element, u32 priority, bool send_back = true) {
+        if (send_back)
+            levels[priority].push_back(element);
+        else
+            levels[priority].push_front(element);
+        used_priorities |= 1ULL << priority;
+    }
+
+    void remove(const T& element, u32 priority) {
+        auto it = ListIterateTo(levels[priority], element);
+        if (it == levels[priority].end())
+            return;
+        levels[priority].erase(it);
+        if (levels[priority].empty()) {
+            used_priorities &= ~(1ULL << priority);
+        }
+    }
+
+    void adjust(const T& element, u32 old_priority, u32 new_priority, bool adjust_front = false) {
+        remove(element, old_priority);
+        add(element, new_priority, !adjust_front);
+    }
+    void adjust(const_iterator it, u32 old_priority, u32 new_priority, bool adjust_front = false) {
+        adjust(*it, old_priority, new_priority, adjust_front);
+    }
+
+    void transfer_to_front(const T& element, u32 priority, MultiLevelQueue& other) {
+        ListSplice(other.levels[priority], other.levels[priority].begin(), levels[priority],
+                   ListIterateTo(levels[priority], element));
+
+        other.used_priorities |= 1ULL << priority;
+
+        if (levels[priority].empty()) {
+            used_priorities &= ~(1ULL << priority);
+        }
+    }
+
+    void transfer_to_front(const_iterator it, u32 priority, MultiLevelQueue& other) {
+        transfer_to_front(*it, priority, other);
+    }
+
+    void transfer_to_back(const T& element, u32 priority, MultiLevelQueue& other) {
+        ListSplice(other.levels[priority], other.levels[priority].end(), levels[priority],
+                   ListIterateTo(levels[priority], element));
+
+        other.used_priorities |= 1ULL << priority;
+
+        if (levels[priority].empty()) {
+            used_priorities &= ~(1ULL << priority);
+        }
+    }
+
+    void transfer_to_back(const_iterator it, u32 priority, MultiLevelQueue& other) {
+        transfer_to_back(*it, priority, other);
+    }
+
+    void yield(u32 priority, std::size_t n = 1) {
+        ListShiftForward(levels[priority], n);
+    }
+
+    std::size_t depth() const {
+        return Depth;
+    }
+
+    std::size_t size(u32 priority) const {
+        return levels[priority].size();
+    }
+
+    std::size_t size() const {
+        u64 priorities = used_priorities;
+        std::size_t size = 0;
+        while (priorities != 0) {
+            const u64 current_priority = CountTrailingZeroes64(priorities);
+            size += levels[current_priority].size();
+            priorities &= ~(1ULL << current_priority);
+        }
+        return size;
+    }
+
+    bool empty() const {
+        return used_priorities == 0;
+    }
+
+    bool empty(u32 priority) const {
+        return (used_priorities & (1ULL << priority)) == 0;
+    }
+
+    u32 highest_priority_set(u32 max_priority = 0) const {
+        const u64 priorities =
+            max_priority == 0 ? used_priorities : (used_priorities & ~((1ULL << max_priority) - 1));
+        return priorities == 0 ? Depth : static_cast<u32>(CountTrailingZeroes64(priorities));
+    }
+
+    u32 lowest_priority_set(u32 min_priority = Depth - 1) const {
+        const u64 priorities = min_priority >= Depth - 1
+                                   ? used_priorities
+                                   : (used_priorities & ((1ULL << (min_priority + 1)) - 1));
+        return priorities == 0 ? Depth : 63 - CountLeadingZeroes64(priorities);
+    }
+
+    const_iterator cbegin(u32 max_prio = 0) const {
+        const u32 priority = highest_priority_set(max_prio);
+        return priority == Depth ? cend()
+                                 : const_iterator{*this, levels[priority].cbegin(), priority};
+    }
+    const_iterator begin(u32 max_prio = 0) const {
+        return cbegin(max_prio);
+    }
+    iterator begin(u32 max_prio = 0) {
+        const u32 priority = highest_priority_set(max_prio);
+        return priority == Depth ? end() : iterator{*this, levels[priority].begin(), priority};
+    }
+
+    const_iterator cend(u32 min_prio = Depth - 1) const {
+        return min_prio == Depth - 1 ? const_iterator{*this, Depth} : cbegin(min_prio + 1);
+    }
+    const_iterator end(u32 min_prio = Depth - 1) const {
+        return cend(min_prio);
+    }
+    iterator end(u32 min_prio = Depth - 1) {
+        return min_prio == Depth - 1 ? iterator{*this, Depth} : begin(min_prio + 1);
+    }
+
+    T& front(u32 max_priority = 0) {
+        const u32 priority = highest_priority_set(max_priority);
+        return levels[priority == Depth ? 0 : priority].front();
+    }
+    const T& front(u32 max_priority = 0) const {
+        const u32 priority = highest_priority_set(max_priority);
+        return levels[priority == Depth ? 0 : priority].front();
+    }
+
+    T back(u32 min_priority = Depth - 1) {
+        const u32 priority = lowest_priority_set(min_priority); // intended
+        return levels[priority == Depth ? 63 : priority].back();
+    }
+    const T& back(u32 min_priority = Depth - 1) const {
+        const u32 priority = lowest_priority_set(min_priority); // intended
+        return levels[priority == Depth ? 63 : priority].back();
+    }
+
+private:
+    using const_list_iterator = typename std::list<T>::const_iterator;
+
+    static void ListShiftForward(std::list<T>& list, const std::size_t shift = 1) {
+        if (shift >= list.size()) {
+            return;
+        }
+
+        const auto begin_range = list.begin();
+        const auto end_range = std::next(begin_range, shift);
+        list.splice(list.end(), list, begin_range, end_range);
+    }
+
+    static void ListSplice(std::list<T>& in_list, const_list_iterator position,
+                           std::list<T>& out_list, const_list_iterator element) {
+        in_list.splice(position, out_list, element);
+    }
+
+    static const_list_iterator ListIterateTo(const std::list<T>& list, const T& element) {
+        auto it = list.cbegin();
+        while (it != list.cend() && *it != element) {
+            ++it;
+        }
+        return it;
+    }
+
+    std::array<std::list<T>, Depth> levels;
+    u64 used_priorities = 0;
+};
+
+} // namespace Common
diff --git a/src/core/hle/kernel/scheduler.cpp b/src/core/hle/kernel/scheduler.cpp
index cc189cc64..6d0f13ecf 100644
--- a/src/core/hle/kernel/scheduler.cpp
+++ b/src/core/hle/kernel/scheduler.cpp
@@ -30,7 +30,7 @@ Scheduler::~Scheduler() {
 
 bool Scheduler::HaveReadyThreads() const {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
-    return ready_queue.get_first() != nullptr;
+    return !ready_queue.empty();
 }
 
 Thread* Scheduler::GetCurrentThread() const {
@@ -46,22 +46,27 @@ Thread* Scheduler::PopNextReadyThread() {
     Thread* thread = GetCurrentThread();
 
     if (thread && thread->GetStatus() == ThreadStatus::Running) {
+        if (ready_queue.empty()) {
+            return thread;
+        }
         // We have to do better than the current thread.
         // This call returns null when that's not possible.
-        next = ready_queue.pop_first_better(thread->GetPriority());
-        if (!next) {
-            // Otherwise just keep going with the current thread
+        next = ready_queue.front();
+        if (next == nullptr || next->GetPriority() >= thread->GetPriority()) {
             next = thread;
         }
     } else {
-        next = ready_queue.pop_first();
+        if (ready_queue.empty()) {
+            return nullptr;
+        }
+        next = ready_queue.front();
     }
 
     return next;
 }
 
 void Scheduler::SwitchContext(Thread* new_thread) {
-    Thread* const previous_thread = GetCurrentThread();
+    Thread* previous_thread = GetCurrentThread();
     Process* const previous_process = system.Kernel().CurrentProcess();
 
     UpdateLastContextSwitchTime(previous_thread, previous_process);
@@ -75,7 +80,7 @@ void Scheduler::SwitchContext(Thread* new_thread) {
         if (previous_thread->GetStatus() == ThreadStatus::Running) {
             // This is only the case when a reschedule is triggered without the current thread
             // yielding execution (i.e. an event triggered, system core time-sliced, etc)
-            ready_queue.push_front(previous_thread->GetPriority(), previous_thread);
+            ready_queue.add(previous_thread, previous_thread->GetPriority(), false);
             previous_thread->SetStatus(ThreadStatus::Ready);
         }
     }
@@ -90,7 +95,7 @@ void Scheduler::SwitchContext(Thread* new_thread) {
 
         current_thread = new_thread;
 
-        ready_queue.remove(new_thread->GetPriority(), new_thread);
+        ready_queue.remove(new_thread, new_thread->GetPriority());
         new_thread->SetStatus(ThreadStatus::Running);
 
         auto* const thread_owner_process = current_thread->GetOwnerProcess();
@@ -147,7 +152,6 @@ void Scheduler::AddThread(SharedPtr<Thread> thread, u32 priority) {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
 
     thread_list.push_back(std::move(thread));
-    ready_queue.prepare(priority);
 }
 
 void Scheduler::RemoveThread(Thread* thread) {
@@ -161,33 +165,37 @@ void Scheduler::ScheduleThread(Thread* thread, u32 priority) {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
 
     ASSERT(thread->GetStatus() == ThreadStatus::Ready);
-    ready_queue.push_back(priority, thread);
+    ready_queue.add(thread, priority);
 }
 
 void Scheduler::UnscheduleThread(Thread* thread, u32 priority) {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
 
     ASSERT(thread->GetStatus() == ThreadStatus::Ready);
-    ready_queue.remove(priority, thread);
+    ready_queue.remove(thread, priority);
 }
 
 void Scheduler::SetThreadPriority(Thread* thread, u32 priority) {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
+    if (thread->GetPriority() == priority) {
+        return;
+    }
 
     // If thread was ready, adjust queues
     if (thread->GetStatus() == ThreadStatus::Ready)
-        ready_queue.move(thread, thread->GetPriority(), priority);
-    else
-        ready_queue.prepare(priority);
+        ready_queue.adjust(thread, thread->GetPriority(), priority);
 }
 
 Thread* Scheduler::GetNextSuggestedThread(u32 core, u32 maximum_priority) const {
     std::lock_guard<std::mutex> lock(scheduler_mutex);
 
     const u32 mask = 1U << core;
-    return ready_queue.get_first_filter([mask, maximum_priority](Thread const* thread) {
-        return (thread->GetAffinityMask() & mask) != 0 && thread->GetPriority() < maximum_priority;
-    });
+    for (auto* thread : ready_queue) {
+        if ((thread->GetAffinityMask() & mask) != 0 && thread->GetPriority() < maximum_priority) {
+            return thread;
+        }
+    }
+    return nullptr;
 }
 
 void Scheduler::YieldWithoutLoadBalancing(Thread* thread) {
diff --git a/src/core/hle/kernel/scheduler.h b/src/core/hle/kernel/scheduler.h
index 1c5bf57d9..44baeb713 100644
--- a/src/core/hle/kernel/scheduler.h
+++ b/src/core/hle/kernel/scheduler.h
@@ -7,7 +7,7 @@
 #include <mutex>
 #include <vector>
 #include "common/common_types.h"
-#include "common/thread_queue_list.h"
+#include "common/multi_level_queue.h"
 #include "core/hle/kernel/object.h"
 #include "core/hle/kernel/thread.h"
 
@@ -156,7 +156,7 @@ private:
     std::vector<SharedPtr<Thread>> thread_list;
 
     /// Lists only ready thread ids.
-    Common::ThreadQueueList<Thread*, THREADPRIO_LOWEST + 1> ready_queue;
+    Common::MultiLevelQueue<Thread*, THREADPRIO_LOWEST + 1> ready_queue;
 
     SharedPtr<Thread> current_thread = nullptr;
 
diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index d0284bdf4..c7038b217 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -1,5 +1,7 @@
 add_executable(tests
     common/bit_field.cpp
+    common/bit_utils.cpp
+    common/multi_level_queue.cpp
     common/param_package.cpp
     common/ring_buffer.cpp
     core/arm/arm_test_common.cpp
diff --git a/src/tests/common/bit_utils.cpp b/src/tests/common/bit_utils.cpp
new file mode 100644
index 000000000..479b5995a
--- /dev/null
+++ b/src/tests/common/bit_utils.cpp
@@ -0,0 +1,23 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <catch2/catch.hpp>
+#include <math.h>
+#include "common/bit_util.h"
+
+namespace Common {
+
+TEST_CASE("BitUtils::CountTrailingZeroes", "[common]") {
+    REQUIRE(Common::CountTrailingZeroes32(0) == 32);
+    REQUIRE(Common::CountTrailingZeroes64(0) == 64);
+    REQUIRE(Common::CountTrailingZeroes32(9) == 0);
+    REQUIRE(Common::CountTrailingZeroes32(8) == 3);
+    REQUIRE(Common::CountTrailingZeroes32(0x801000) == 12);
+    REQUIRE(Common::CountTrailingZeroes64(9) == 0);
+    REQUIRE(Common::CountTrailingZeroes64(8) == 3);
+    REQUIRE(Common::CountTrailingZeroes64(0x801000) == 12);
+    REQUIRE(Common::CountTrailingZeroes64(0x801000000000UL) == 36);
+}
+
+} // namespace Common
diff --git a/src/tests/common/multi_level_queue.cpp b/src/tests/common/multi_level_queue.cpp
new file mode 100644
index 000000000..cca7ec7da
--- /dev/null
+++ b/src/tests/common/multi_level_queue.cpp
@@ -0,0 +1,55 @@
+// Copyright 2019 Yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <catch2/catch.hpp>
+#include <math.h>
+#include "common/common_types.h"
+#include "common/multi_level_queue.h"
+
+namespace Common {
+
+TEST_CASE("MultiLevelQueue", "[common]") {
+    std::array<f32, 8> values = {0.0, 5.0, 1.0, 9.0, 8.0, 2.0, 6.0, 7.0};
+    Common::MultiLevelQueue<f32, 64> mlq;
+    REQUIRE(mlq.empty());
+    mlq.add(values[2], 2);
+    mlq.add(values[7], 7);
+    mlq.add(values[3], 3);
+    mlq.add(values[4], 4);
+    mlq.add(values[0], 0);
+    mlq.add(values[5], 5);
+    mlq.add(values[6], 6);
+    mlq.add(values[1], 1);
+    u32 index = 0;
+    bool all_set = true;
+    for (auto& f : mlq) {
+        all_set &= (f == values[index]);
+        index++;
+    }
+    REQUIRE(all_set);
+    REQUIRE(!mlq.empty());
+    f32 v = 8.0;
+    mlq.add(v, 2);
+    v = -7.0;
+    mlq.add(v, 2, false);
+    REQUIRE(mlq.front(2) == -7.0);
+    mlq.yield(2);
+    REQUIRE(mlq.front(2) == values[2]);
+    REQUIRE(mlq.back(2) == -7.0);
+    REQUIRE(mlq.empty(8));
+    v = 10.0;
+    mlq.add(v, 8);
+    mlq.adjust(v, 8, 9);
+    REQUIRE(mlq.front(9) == v);
+    REQUIRE(mlq.empty(8));
+    REQUIRE(!mlq.empty(9));
+    mlq.adjust(values[0], 0, 9);
+    REQUIRE(mlq.highest_priority_set() == 1);
+    REQUIRE(mlq.lowest_priority_set() == 9);
+    mlq.remove(values[1], 1);
+    REQUIRE(mlq.highest_priority_set() == 2);
+    REQUIRE(mlq.empty(1));
+}
+
+} // namespace Common