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8199781: Don't use naked == for comparing oops

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Reviewed-by: coleenp, eosterlund, jrose
This commit is contained in:
Roman Kennke 2018-04-03 13:15:27 +02:00
parent 8b50176bdc
commit b938ae51ce
36 changed files with 1484 additions and 1282 deletions
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412
src/hotspot/share/oops/access.hpp
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@ -22,16 +22,17 @@
*
*/
#ifndef SHARE_VM_RUNTIME_ACCESS_HPP
#define SHARE_VM_RUNTIME_ACCESS_HPP
#ifndef SHARE_OOPS_ACCESS_HPP
#define SHARE_OOPS_ACCESS_HPP
#include "memory/allocation.hpp"
#include "metaprogramming/decay.hpp"
#include "metaprogramming/integralConstant.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.
@ -39,11 +40,12 @@
// 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.
// 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.
@ -56,329 +58,39 @@
// * 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.
// * equals: Object equality, e.g. when different copies of the same objects are in use (from-space vs. to-space)
//
// === 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);
template <DecoratorSet decorators, typename T>
T atomic_cmpxchg_at(T new_value, oop base, ptrdiff_t offset, T compare_value);
template <DecoratorSet decorators, typename T>
T atomic_xchg_at(T new_value, oop base, ptrdiff_t offset);
template <DecoratorSet decorators, typename P, typename T>
void store(P* addr, T value);
template <DecoratorSet decorators, typename P, typename T>
T load(P* addr);
template <DecoratorSet decorators, typename P, typename T>
T atomic_cmpxchg(T new_value, P* addr, T compare_value);
template <DecoratorSet decorators, typename P, typename T>
T atomic_xchg(T new_value, P* addr);
template <DecoratorSet decorators, typename T>
bool arraycopy(arrayOop src_obj, arrayOop dst_obj, T *src, T *dst, size_t length);
template <DecoratorSet decorators>
void clone(oop src, oop dst, size_t size);
template <DecoratorSet decorators>
oop resolve(oop src);
// Infer the type that should be returned from a load.
template <typename P, DecoratorSet decorators>
class OopLoadProxy: public StackObj {
private:
P *const _addr;
public:
OopLoadProxy(P* addr) : _addr(addr) {}
inline operator oop() {
return load<decorators | INTERNAL_VALUE_IS_OOP, P, oop>(_addr);
}
inline operator narrowOop() {
return load<decorators | INTERNAL_VALUE_IS_OOP, P, narrowOop>(_addr);
}
template <typename T>
inline bool operator ==(const T& other) const {
return load<decorators | INTERNAL_VALUE_IS_OOP, P, T>(_addr) == other;
}
template <typename T>
inline bool operator !=(const T& other) const {
return load<decorators | INTERNAL_VALUE_IS_OOP, P, T>(_addr) != other;
}
};
// Infer the type that should be returned from a load_at.
template <DecoratorSet decorators>
class LoadAtProxy: public StackObj {
private:
const oop _base;
const ptrdiff_t _offset;
public:
LoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}
template <typename T>
inline operator T() const {
return load_at<decorators, T>(_base, _offset);
}
template <typename T>
inline bool operator ==(const T& other) const { return load_at<decorators, T>(_base, _offset) == other; }
template <typename T>
inline bool operator !=(const T& other) const { return load_at<decorators, T>(_base, _offset) != other; }
};
template <DecoratorSet decorators>
class OopLoadAtProxy: public StackObj {
private:
const oop _base;
const ptrdiff_t _offset;
public:
OopLoadAtProxy(oop base, ptrdiff_t offset) : _base(base), _offset(offset) {}
inline operator oop() const {
return load_at<decorators | INTERNAL_VALUE_IS_OOP, oop>(_base, _offset);
}
inline operator narrowOop() const {
return load_at<decorators | INTERNAL_VALUE_IS_OOP, narrowOop>(_base, _offset);
}
template <typename T>
inline bool operator ==(const T& other) const {
return load_at<decorators | INTERNAL_VALUE_IS_OOP, T>(_base, _offset) == other;
}
template <typename T>
inline bool operator !=(const T& other) const {
return load_at<decorators | INTERNAL_VALUE_IS_OOP, T>(_base, _offset) != other;
}
};
}
// == 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.
template <DecoratorSet decorators = INTERNAL_EMPTY>
class Access: public AllStatic {
@ -554,6 +266,11 @@ public:
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
@ -571,4 +288,41 @@ class HeapAccess: public Access<IN_HEAP | decorators> {};
template <DecoratorSet decorators = INTERNAL_EMPTY>
class RootAccess: public Access<IN_ROOT | decorators> {};
#endif // SHARE_VM_RUNTIME_ACCESS_HPP
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