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src/hotspot/share/oops/access.hpp

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*** 20,51 **** * or visit www.oracle.com if you need additional information or have any * questions. * */ ! #ifndef SHARE_VM_RUNTIME_ACCESS_HPP ! #define SHARE_VM_RUNTIME_ACCESS_HPP #include "memory/allocation.hpp" ! #include "metaprogramming/decay.hpp" ! #include "metaprogramming/integralConstant.hpp" #include "oops/oopsHierarchy.hpp" #include "utilities/debug.hpp" #include "utilities/globalDefinitions.hpp" // = GENERAL = // Access is an API for performing accesses with declarative semantics. Each access can have a number of "decorators". // A decorator is an attribute or property that affects the way a memory access is performed in some way. // There are different groups of decorators. Some have to do with memory ordering, others to do with, // e.g. strength of references, strength of GC barriers, or whether compression should be applied or not. // Some decorators are set at buildtime, such as whether primitives require GC barriers or not, others // at callsites such as whether an access is in the heap or not, and others are resolved at runtime ! // such as GC-specific barriers and encoding/decoding compressed oops. // By pipelining handling of these decorators, the design of the Access API allows separation of concern // over the different orthogonal concerns of decorators, while providing a powerful way of // expressing these orthogonal semantic properties in a unified way. ! // == OPERATIONS == // * load: Load a value from an address. // * load_at: Load a value from an internal pointer relative to a base object. // * store: Store a value at an address. // * store_at: Store a value in an internal pointer relative to a base object. --- 20,53 ---- * or visit www.oracle.com if you need additional information or have any * questions. * */ ! #ifndef SHARE_OOPS_ACCESS_HPP ! #define SHARE_OOPS_ACCESS_HPP #include "memory/allocation.hpp" ! #include "oops/accessBackend.hpp" ! #include "oops/accessDecorators.hpp" #include "oops/oopsHierarchy.hpp" #include "utilities/debug.hpp" #include "utilities/globalDefinitions.hpp" + // = GENERAL = // Access is an API for performing accesses with declarative semantics. Each access can have a number of "decorators". // A decorator is an attribute or property that affects the way a memory access is performed in some way. // There are different groups of decorators. Some have to do with memory ordering, others to do with, // e.g. strength of references, strength of GC barriers, or whether compression should be applied or not. // Some decorators are set at buildtime, such as whether primitives require GC barriers or not, others // at callsites such as whether an access is in the heap or not, and others are resolved at runtime ! // such as GC-specific barriers and encoding/decoding compressed oops. For more information about what ! // decorators are available, cf. oops/accessDecorators.hpp. // By pipelining handling of these decorators, the design of the Access API allows separation of concern // over the different orthogonal concerns of decorators, while providing a powerful way of // expressing these orthogonal semantic properties in a unified way. ! // // == OPERATIONS == // * load: Load a value from an address. // * load_at: Load a value from an internal pointer relative to a base object. // * store: Store a value at an address. // * store_at: Store a value in an internal pointer relative to a base object. ***************
*** 54,278 **** // * atomic_xchg: Atomically swap a new value at an address if previous value matched the compared value. // * atomic_xchg_at: Atomically swap a new value at an internal pointer address if previous value matched the compared value. // * arraycopy: Copy data from one heap array to another heap array. // * clone: Clone the contents of an object to a newly allocated object. // * resolve: Resolve a stable to-space invariant oop that is guaranteed not to relocate its payload until a subsequent thread transition. ! ! typedef uint64_t DecoratorSet; ! ! // == Internal Decorators - do not use == ! // * INTERNAL_EMPTY: This is the name for the empty decorator set (in absence of other decorators). ! // * INTERNAL_CONVERT_COMPRESSED_OOPS: This is an oop access that will require converting an oop ! // to a narrowOop or vice versa, if UseCompressedOops is known to be set. ! // * INTERNAL_VALUE_IS_OOP: Remember that the involved access is on oop rather than primitive. ! const DecoratorSet INTERNAL_EMPTY = UCONST64(0); ! const DecoratorSet INTERNAL_CONVERT_COMPRESSED_OOP = UCONST64(1) << 1; ! const DecoratorSet INTERNAL_VALUE_IS_OOP = UCONST64(1) << 2; ! ! // == Internal build-time Decorators == ! // * INTERNAL_BT_BARRIER_ON_PRIMITIVES: This is set in the barrierSetConfig.hpp file. ! // * INTERNAL_BT_TO_SPACE_INVARIANT: This is set in the barrierSetConfig.hpp file iff ! // no GC is bundled in the build that is to-space invariant. ! const DecoratorSet INTERNAL_BT_BARRIER_ON_PRIMITIVES = UCONST64(1) << 3; ! const DecoratorSet INTERNAL_BT_TO_SPACE_INVARIANT = UCONST64(1) << 4; ! ! // == Internal run-time Decorators == ! // * INTERNAL_RT_USE_COMPRESSED_OOPS: This decorator will be set in runtime resolved ! // access backends iff UseCompressedOops is true. ! const DecoratorSet INTERNAL_RT_USE_COMPRESSED_OOPS = UCONST64(1) << 5; ! ! const DecoratorSet INTERNAL_DECORATOR_MASK = INTERNAL_CONVERT_COMPRESSED_OOP | INTERNAL_VALUE_IS_OOP | ! INTERNAL_BT_BARRIER_ON_PRIMITIVES | INTERNAL_RT_USE_COMPRESSED_OOPS; ! ! // == Memory Ordering Decorators == ! // The memory ordering decorators can be described in the following way: ! // === Decorator Rules === ! // The different types of memory ordering guarantees have a strict order of strength. ! // Explicitly specifying the stronger ordering implies that the guarantees of the weaker ! // property holds too. The names come from the C++11 atomic operations, and typically ! // have a JMM equivalent property. ! // The equivalence may be viewed like this: ! // MO_UNORDERED is equivalent to JMM plain. ! // MO_VOLATILE has no equivalence in JMM, because it's a C++ thing. ! // MO_RELAXED is equivalent to JMM opaque. ! // MO_ACQUIRE is equivalent to JMM acquire. ! // MO_RELEASE is equivalent to JMM release. ! // MO_SEQ_CST is equivalent to JMM volatile. // ! // === Stores === ! // * MO_UNORDERED (Default): No guarantees. ! // - The compiler and hardware are free to reorder aggressively. And they will. ! // * MO_VOLATILE: Volatile stores (in the C++ sense). ! // - The stores are not reordered by the compiler (but possibly the HW) w.r.t. other ! // volatile accesses in program order (but possibly non-volatile accesses). ! // * MO_RELAXED: Relaxed atomic stores. ! // - The stores are atomic. ! // - Guarantees from volatile stores hold. ! // * MO_RELEASE: Releasing stores. ! // - The releasing store will make its preceding memory accesses observable to memory accesses ! // subsequent to an acquiring load observing this releasing store. ! // - Guarantees from relaxed stores hold. ! // * MO_SEQ_CST: Sequentially consistent stores. ! // - The stores are observed in the same order by MO_SEQ_CST loads on other processors ! // - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order. ! // - Guarantees from releasing stores hold. ! // === Loads === ! // * MO_UNORDERED (Default): No guarantees ! // - The compiler and hardware are free to reorder aggressively. And they will. ! // * MO_VOLATILE: Volatile loads (in the C++ sense). ! // - The loads are not reordered by the compiler (but possibly the HW) w.r.t. other ! // volatile accesses in program order (but possibly non-volatile accesses). ! // * MO_RELAXED: Relaxed atomic loads. ! // - The stores are atomic. ! // - Guarantees from volatile loads hold. ! // * MO_ACQUIRE: Acquiring loads. ! // - An acquiring load will make subsequent memory accesses observe the memory accesses ! // preceding the releasing store that the acquiring load observed. ! // - Guarantees from relaxed loads hold. ! // * MO_SEQ_CST: Sequentially consistent loads. ! // - These loads observe MO_SEQ_CST stores in the same order on other processors ! // - Preceding loads and stores in program order are not reordered with subsequent loads and stores in program order. ! // - Guarantees from acquiring loads hold. ! // === Atomic Cmpxchg === ! // * MO_RELAXED: Atomic but relaxed cmpxchg. ! // - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold unconditionally. ! // * MO_SEQ_CST: Sequentially consistent cmpxchg. ! // - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold unconditionally. ! // === Atomic Xchg === ! // * MO_RELAXED: Atomic but relaxed atomic xchg. ! // - Guarantees from MO_RELAXED loads and MO_RELAXED stores hold. ! // * MO_SEQ_CST: Sequentially consistent xchg. ! // - Guarantees from MO_SEQ_CST loads and MO_SEQ_CST stores hold. ! const DecoratorSet MO_UNORDERED = UCONST64(1) << 6; ! const DecoratorSet MO_VOLATILE = UCONST64(1) << 7; ! const DecoratorSet MO_RELAXED = UCONST64(1) << 8; ! const DecoratorSet MO_ACQUIRE = UCONST64(1) << 9; ! const DecoratorSet MO_RELEASE = UCONST64(1) << 10; ! const DecoratorSet MO_SEQ_CST = UCONST64(1) << 11; ! const DecoratorSet MO_DECORATOR_MASK = MO_UNORDERED | MO_VOLATILE | MO_RELAXED | ! MO_ACQUIRE | MO_RELEASE | MO_SEQ_CST; ! ! // === Barrier Strength Decorators === ! // * AS_RAW: The access will translate into a raw memory access, hence ignoring all semantic concerns ! // except memory ordering and compressed oops. This will bypass runtime function pointer dispatching ! // in the pipeline and hardwire to raw accesses without going trough the GC access barriers. ! // - Accesses on oop* translate to raw memory accesses without runtime checks ! // - Accesses on narrowOop* translate to encoded/decoded memory accesses without runtime checks ! // - Accesses on HeapWord* translate to a runtime check choosing one of the above ! // - Accesses on other types translate to raw memory accesses without runtime checks ! // * AS_DEST_NOT_INITIALIZED: This property can be important to e.g. SATB barriers by ! // marking that the previous value is uninitialized nonsense rather than a real value. ! // * AS_NO_KEEPALIVE: The barrier is used only on oop references and will not keep any involved objects ! // alive, regardless of the type of reference being accessed. It will however perform the memory access ! // in a consistent way w.r.t. e.g. concurrent compaction, so that the right field is being accessed, ! // or maintain, e.g. intergenerational or interregional pointers if applicable. This should be used with ! // extreme caution in isolated scopes. ! // * AS_NORMAL: The accesses will be resolved to an accessor on the BarrierSet class, giving the ! // responsibility of performing the access and what barriers to be performed to the GC. This is the default. ! // Note that primitive accesses will only be resolved on the barrier set if the appropriate build-time ! // decorator for enabling primitive barriers is enabled for the build. ! const DecoratorSet AS_RAW = UCONST64(1) << 12; ! const DecoratorSet AS_DEST_NOT_INITIALIZED = UCONST64(1) << 13; ! const DecoratorSet AS_NO_KEEPALIVE = UCONST64(1) << 14; ! const DecoratorSet AS_NORMAL = UCONST64(1) << 15; ! const DecoratorSet AS_DECORATOR_MASK = AS_RAW | AS_DEST_NOT_INITIALIZED | ! AS_NO_KEEPALIVE | AS_NORMAL; ! ! // === Reference Strength Decorators === ! // These decorators only apply to accesses on oop-like types (oop/narrowOop). ! // * ON_STRONG_OOP_REF: Memory access is performed on a strongly reachable reference. ! // * ON_WEAK_OOP_REF: The memory access is performed on a weakly reachable reference. ! // * ON_PHANTOM_OOP_REF: The memory access is performed on a phantomly reachable reference. ! // This is the same ring of strength as jweak and weak oops in the VM. ! // * ON_UNKNOWN_OOP_REF: The memory access is performed on a reference of unknown strength. ! // This could for example come from the unsafe API. ! // * Default (no explicit reference strength specified): ON_STRONG_OOP_REF ! const DecoratorSet ON_STRONG_OOP_REF = UCONST64(1) << 16; ! const DecoratorSet ON_WEAK_OOP_REF = UCONST64(1) << 17; ! const DecoratorSet ON_PHANTOM_OOP_REF = UCONST64(1) << 18; ! const DecoratorSet ON_UNKNOWN_OOP_REF = UCONST64(1) << 19; ! const DecoratorSet ON_DECORATOR_MASK = ON_STRONG_OOP_REF | ON_WEAK_OOP_REF | ! ON_PHANTOM_OOP_REF | ON_UNKNOWN_OOP_REF; ! ! // === Access Location === ! // Accesses can take place in, e.g. the heap, old or young generation and different native roots. ! // The location is important to the GC as it may imply different actions. The following decorators are used: ! // * IN_HEAP: The access is performed in the heap. Many barriers such as card marking will ! // be omitted if this decorator is not set. ! // * IN_HEAP_ARRAY: The access is performed on a heap allocated array. This is sometimes a special case ! // for some GCs, and implies that it is an IN_HEAP. ! // * IN_ROOT: The access is performed in an off-heap data structure pointing into the Java heap. ! // * IN_CONCURRENT_ROOT: The access is performed in an off-heap data structure pointing into the Java heap, ! // but is notably not scanned during safepoints. This is sometimes a special case for some GCs and ! // implies that it is also an IN_ROOT. ! const DecoratorSet IN_HEAP = UCONST64(1) << 20; ! const DecoratorSet IN_HEAP_ARRAY = UCONST64(1) << 21; ! const DecoratorSet IN_ROOT = UCONST64(1) << 22; ! const DecoratorSet IN_CONCURRENT_ROOT = UCONST64(1) << 23; ! const DecoratorSet IN_ARCHIVE_ROOT = UCONST64(1) << 24; ! const DecoratorSet IN_DECORATOR_MASK = IN_HEAP | IN_HEAP_ARRAY | ! IN_ROOT | IN_CONCURRENT_ROOT | ! IN_ARCHIVE_ROOT; ! ! // == Value Decorators == ! // * OOP_NOT_NULL: This property can make certain barriers faster such as compressing oops. ! const DecoratorSet OOP_NOT_NULL = UCONST64(1) << 25; ! const DecoratorSet OOP_DECORATOR_MASK = OOP_NOT_NULL; ! ! // == Arraycopy Decorators == ! // * ARRAYCOPY_CHECKCAST: This property means that the class of the objects in source ! // are not guaranteed to be subclasses of the class of the destination array. This requires ! // a check-cast barrier during the copying operation. If this is not set, it is assumed ! // that the array is covariant: (the source array type is-a destination array type) ! // * ARRAYCOPY_DISJOINT: This property means that it is known that the two array ranges ! // are disjoint. ! // * ARRAYCOPY_ARRAYOF: The copy is in the arrayof form. ! // * ARRAYCOPY_ATOMIC: The accesses have to be atomic over the size of its elements. ! // * ARRAYCOPY_ALIGNED: The accesses have to be aligned on a HeapWord. ! const DecoratorSet ARRAYCOPY_CHECKCAST = UCONST64(1) << 26; ! const DecoratorSet ARRAYCOPY_DISJOINT = UCONST64(1) << 27; ! const DecoratorSet ARRAYCOPY_ARRAYOF = UCONST64(1) << 28; ! const DecoratorSet ARRAYCOPY_ATOMIC = UCONST64(1) << 29; ! const DecoratorSet ARRAYCOPY_ALIGNED = UCONST64(1) << 30; ! const DecoratorSet ARRAYCOPY_DECORATOR_MASK = ARRAYCOPY_CHECKCAST | ARRAYCOPY_DISJOINT | ! ARRAYCOPY_DISJOINT | ARRAYCOPY_ARRAYOF | ! ARRAYCOPY_ATOMIC | ARRAYCOPY_ALIGNED; ! ! // The HasDecorator trait can help at compile-time determining whether a decorator set ! // has an intersection with a certain other decorator set ! template <DecoratorSet decorators, DecoratorSet decorator> ! struct HasDecorator: public IntegralConstant<bool, (decorators & decorator) != 0> {}; namespace AccessInternal { - template <typename T> - struct OopOrNarrowOopInternal: AllStatic { - typedef oop type; - }; - - template <> - struct OopOrNarrowOopInternal<narrowOop>: AllStatic { - typedef narrowOop type; - }; - - // This metafunction returns a canonicalized oop/narrowOop type for a passed - // in oop-like types passed in from oop_* overloads where the user has sworn - // that the passed in values should be oop-like (e.g. oop, oopDesc*, arrayOop, - // narrowOoop, instanceOopDesc*, and random other things). - // In the oop_* overloads, it must hold that if the passed in type T is not - // narrowOop, then it by contract has to be one of many oop-like types implicitly - // convertible to oop, and hence returns oop as the canonical oop type. - // If it turns out it was not, then the implicit conversion to oop will fail - // to compile, as desired. - template <typename T> - struct OopOrNarrowOop: AllStatic { - typedef typename OopOrNarrowOopInternal<typename Decay<T>::type>::type type; - }; - - inline void* field_addr(oop base, ptrdiff_t byte_offset) { - return reinterpret_cast<void*>(reinterpret_cast<intptr_t>((void*)base) + byte_offset); - } - template <DecoratorSet decorators, typename T> void store_at(oop base, ptrdiff_t offset, T value); template <DecoratorSet decorators, typename T> T load_at(oop base, ptrdiff_t offset); --- 56,100 ---- // * atomic_xchg: Atomically swap a new value at an address if previous value matched the compared value. // * atomic_xchg_at: Atomically swap a new value at an internal pointer address if previous value matched the compared value. // * arraycopy: Copy data from one heap array to another heap array. // * clone: Clone the contents of an object to a newly allocated object. // * resolve: Resolve a stable to-space invariant oop that is guaranteed not to relocate its payload until a subsequent thread transition. ! // * equals: Object equality, e.g. when different copies of the same objects are in use (from-space vs. to-space) ! // ! // == IMPLEMENTATION == ! // Each access goes through the following steps in a template pipeline. ! // There are essentially 5 steps for each access: ! // * Step 1: Set default decorators and decay types. This step gets rid of CV qualifiers ! // and sets default decorators to sensible values. ! // * Step 2: Reduce types. This step makes sure there is only a single T type and not ! // multiple types. The P type of the address and T type of the value must ! // match. ! // * Step 3: Pre-runtime dispatch. This step checks whether a runtime call can be ! // avoided, and in that case avoids it (calling raw accesses or ! // primitive accesses in a build that does not require primitive GC barriers) ! // * Step 4: Runtime-dispatch. This step performs a runtime dispatch to the corresponding ! // BarrierSet::AccessBarrier accessor that attaches GC-required barriers ! // to the access. ! // * Step 5.a: Barrier resolution. This step is invoked the first time a runtime-dispatch ! // happens for an access. The appropriate BarrierSet::AccessBarrier accessor ! // is resolved, then the function pointer is updated to that accessor for ! // future invocations. ! // * Step 5.b: Post-runtime dispatch. This step now casts previously unknown types such ! // as the address type of an oop on the heap (is it oop* or narrowOop*) to ! // the appropriate type. It also splits sufficiently orthogonal accesses into ! // different functions, such as whether the access involves oops or primitives ! // and whether the access is performed on the heap or outside. Then the ! // appropriate BarrierSet::AccessBarrier is called to perform the access. // ! // The implementation of step 1-4 resides in in accessBackend.hpp, to allow selected ! // accesses to be accessible from only access.hpp, as opposed to access.inline.hpp. ! // Steps 5.a and 5.b require knowledge about the GC backends, and therefore needs to ! // include the various GC backend .inline.hpp headers. Their implementation resides in ! // access.inline.hpp. The accesses that are allowed through the access.hpp file ! // must be instantiated in access.cpp using the INSTANTIATE_HPP_ACCESS macro. namespace AccessInternal { template <DecoratorSet decorators, typename T> void store_at(oop base, ptrdiff_t offset, T value); template <DecoratorSet decorators, typename T> T load_at(oop base, ptrdiff_t offset); ***************
*** 302,311 **** --- 124,136 ---- void clone(oop src, oop dst, size_t size); template <DecoratorSet decorators> oop resolve(oop src); + template <DecoratorSet decorators> + bool equals(oop o1, oop o2); + // Infer the type that should be returned from a load. template <typename P, DecoratorSet decorators> class OopLoadProxy: public StackObj { private: P *const _addr; ***************
*** 552,561 **** --- 377,391 ---- static oop resolve(oop obj) { verify_decorators<INTERNAL_EMPTY>(); return AccessInternal::resolve<decorators>(obj); } + + static bool equals(oop o1, oop o2) { + verify_decorators<INTERNAL_EMPTY>(); + return AccessInternal::equals<decorators>(o1, o2); + } }; // Helper for performing raw accesses (knows only of memory ordering // atomicity decorators as well as compressed oops) template <DecoratorSet decorators = INTERNAL_EMPTY> ***************
*** 569,574 **** // Helper for performing normal accesses in roots. These accesses // may resolve an accessor on a GC barrier set template <DecoratorSet decorators = INTERNAL_EMPTY> class RootAccess: public Access<IN_ROOT | decorators> {}; ! #endif // SHARE_VM_RUNTIME_ACCESS_HPP --- 399,441 ---- // Helper for performing normal accesses in roots. These accesses // may resolve an accessor on a GC barrier set template <DecoratorSet decorators = INTERNAL_EMPTY> class RootAccess: public Access<IN_ROOT | decorators> {}; ! template <DecoratorSet decorators> ! template <DecoratorSet expected_decorators> ! void Access<decorators>::verify_decorators() { ! STATIC_ASSERT((~expected_decorators & decorators) == 0); // unexpected decorator used ! const DecoratorSet barrier_strength_decorators = decorators & AS_DECORATOR_MASK; ! STATIC_ASSERT(barrier_strength_decorators == 0 || ( // make sure barrier strength decorators are disjoint if set ! (barrier_strength_decorators ^ AS_NO_KEEPALIVE) == 0 || ! (barrier_strength_decorators ^ AS_DEST_NOT_INITIALIZED) == 0 || ! (barrier_strength_decorators ^ AS_RAW) == 0 || ! (barrier_strength_decorators ^ AS_NORMAL) == 0 ! )); ! const DecoratorSet ref_strength_decorators = decorators & ON_DECORATOR_MASK; ! STATIC_ASSERT(ref_strength_decorators == 0 || ( // make sure ref strength decorators are disjoint if set ! (ref_strength_decorators ^ ON_STRONG_OOP_REF) == 0 || ! (ref_strength_decorators ^ ON_WEAK_OOP_REF) == 0 || ! (ref_strength_decorators ^ ON_PHANTOM_OOP_REF) == 0 || ! (ref_strength_decorators ^ ON_UNKNOWN_OOP_REF) == 0 ! )); ! const DecoratorSet memory_ordering_decorators = decorators & MO_DECORATOR_MASK; ! STATIC_ASSERT(memory_ordering_decorators == 0 || ( // make sure memory ordering decorators are disjoint if set ! (memory_ordering_decorators ^ MO_UNORDERED) == 0 || ! (memory_ordering_decorators ^ MO_VOLATILE) == 0 || ! (memory_ordering_decorators ^ MO_RELAXED) == 0 || ! (memory_ordering_decorators ^ MO_ACQUIRE) == 0 || ! (memory_ordering_decorators ^ MO_RELEASE) == 0 || ! (memory_ordering_decorators ^ MO_SEQ_CST) == 0 ! )); ! const DecoratorSet location_decorators = decorators & IN_DECORATOR_MASK; ! STATIC_ASSERT(location_decorators == 0 || ( // make sure location decorators are disjoint if set ! (location_decorators ^ IN_ROOT) == 0 || ! (location_decorators ^ IN_HEAP) == 0 || ! (location_decorators ^ (IN_HEAP | IN_HEAP_ARRAY)) == 0 || ! (location_decorators ^ (IN_ROOT | IN_CONCURRENT_ROOT)) == 0 || ! (location_decorators ^ (IN_ROOT | IN_ARCHIVE_ROOT)) == 0 ! )); ! } ! ! #endif // SHARE_OOPS_ACCESS_HPP
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