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https://github.com/Atmosphere-NX/Atmosphere
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kern: devirtualize KAutoObject::DynamicCast<>()
This is an optimization that saves the most common type of virtual call in the kernel (DynamicCast) by storing class token as a member, rather than getting it via virtual call every time. This does not currently cost any memory space on 64-bit targets, due to pre-existing padding space. This optimization can be turned off via a compile-time flag for accuracy.
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parent
26c02e2019
commit
bfffe6b119
3 changed files with 40 additions and 4 deletions
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@ -32,3 +32,10 @@
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//#define MESOSPHERE_BUILD_FOR_TRACING
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#define MESOSPHERE_ENABLE_PANIC_REGISTER_DUMP
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#define MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP
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/* NOTE: This enables fast class token storage using a class member. */
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/* This saves a virtual call when doing KAutoObject->DynCast<>(), */
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/* at the cost of storing class tokens inside the class object. */
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/* However, as of (10/16/2021) KAutoObject has an unused class member */
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/* of the right side, and so this does not actually cost any space. */
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#define MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST
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@ -63,7 +63,11 @@ namespace ams::kern {
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}
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constexpr ALWAYS_INLINE bool IsDerivedFrom(const TypeObj &rhs) {
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return (this->GetClassToken() | rhs.GetClassToken()) == this->GetClassToken();
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return IsClassTokenDerivedFrom(this->GetClassToken(), rhs.GetClassToken());
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}
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static constexpr ALWAYS_INLINE bool IsClassTokenDerivedFrom(ClassTokenType derived, ClassTokenType base) {
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return (derived | base) == derived;
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}
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};
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private:
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@ -71,11 +75,23 @@ namespace ams::kern {
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private:
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KAutoObject *m_next_closed_object;
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std::atomic<u32> m_ref_count;
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#if defined(MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST)
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ClassTokenType m_class_token;
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#else
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u32 m_reserved;
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#endif
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public:
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static KAutoObject *Create(KAutoObject *ptr);
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public:
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constexpr ALWAYS_INLINE explicit KAutoObject() : m_next_closed_object(nullptr), m_ref_count(0), m_reserved(0) { MESOSPHERE_ASSERT_THIS(); }
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constexpr ALWAYS_INLINE explicit KAutoObject() : m_next_closed_object(nullptr), m_ref_count(0),
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#if defined(MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST)
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m_class_token(0)
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#else
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m_reserved(0)
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#endif
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{
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MESOSPHERE_ASSERT_THIS();
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}
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/* Destroy is responsible for destroying the auto object's resources when ref_count hits zero. */
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virtual void Destroy() { MESOSPHERE_ASSERT_THIS(); }
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@ -90,11 +106,19 @@ namespace ams::kern {
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}
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ALWAYS_INLINE bool IsDerivedFrom(const TypeObj &rhs) const {
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return this->GetTypeObj().IsDerivedFrom(rhs);
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#if defined(MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST)
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return TypeObj::IsClassTokenDerivedFrom(m_class_token, rhs.GetClassToken());
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#else
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return this->GetTypeObj().IsDerivedFrom(rhs);
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#endif
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}
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ALWAYS_INLINE bool IsDerivedFrom(const KAutoObject &rhs) const {
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return this->IsDerivedFrom(rhs.GetTypeObj());
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#if defined(MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST)
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return TypeObj::IsClassTokenDerivedFrom(m_class_token, rhs.m_class_token);
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#else
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return this->IsDerivedFrom(rhs.GetTypeObj());
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#endif
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}
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template<typename Derived>
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@ -19,6 +19,11 @@ namespace ams::kern {
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KAutoObject *KAutoObject::Create(KAutoObject *obj) {
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obj->m_ref_count = 1;
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#if defined(MESOSPHERE_ENABLE_DEVIRTUALIZED_DYNAMIC_CAST)
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obj->m_class_token = obj->GetTypeObj().GetClassToken();
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#endif
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return obj;
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}
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