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J. Duke 2007-12-01 00:00:00 +00:00
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/*
* Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
//** Dependencies represent assertions (approximate invariants) within
// the class hierarchy. An example is an assertion that a given
// method is not overridden; another example is that a type has only
// one concrete subtype. Compiled code which relies on such
// assertions must be discarded if they are overturned by changes in
// the class hierarchy. We can think of these assertions as
// approximate invariants, because we expect them to be overturned
// very infrequently. We are willing to perform expensive recovery
// operations when they are overturned. The benefit, of course, is
// performing optimistic optimizations (!) on the object code.
//
// Changes in the class hierarchy due to dynamic linking or
// class evolution can violate dependencies. There is enough
// indexing between classes and nmethods to make dependency
// checking reasonably efficient.
class ciEnv;
class nmethod;
class OopRecorder;
class xmlStream;
class CompileLog;
class DepChange;
class No_Safepoint_Verifier;
class Dependencies: public ResourceObj {
public:
// Note: In the comments on dependency types, most uses of the terms
// subtype and supertype are used in a "non-strict" or "inclusive"
// sense, and are starred to remind the reader of this fact.
// Strict uses of the terms use the word "proper".
//
// Specifically, every class is its own subtype* and supertype*.
// (This trick is easier than continually saying things like "Y is a
// subtype of X or X itself".)
//
// Sometimes we write X > Y to mean X is a proper supertype of Y.
// The notation X > {Y, Z} means X has proper subtypes Y, Z.
// The notation X.m > Y means that Y inherits m from X, while
// X.m > Y.m means Y overrides X.m. A star denotes abstractness,
// as *I > A, meaning (abstract) interface I is a super type of A,
// or A.*m > B.m, meaning B.m implements abstract method A.m.
//
// In this module, the terms "subtype" and "supertype" refer to
// Java-level reference type conversions, as detected by
// "instanceof" and performed by "checkcast" operations. The method
// Klass::is_subtype_of tests these relations. Note that "subtype"
// is richer than "subclass" (as tested by Klass::is_subclass_of),
// since it takes account of relations involving interface and array
// types.
//
// To avoid needless complexity, dependencies involving array types
// are not accepted. If you need to make an assertion about an
// array type, make the assertion about its corresponding element
// types. Any assertion that might change about an array type can
// be converted to an assertion about its element type.
//
// Most dependencies are evaluated over a "context type" CX, which
// stands for the set Subtypes(CX) of every Java type that is a subtype*
// of CX. When the system loads a new class or interface N, it is
// responsible for re-evaluating changed dependencies whose context
// type now includes N, that is, all super types of N.
//
enum DepType {
end_marker = 0,
// An 'evol' dependency simply notes that the contents of the
// method were used. If it evolves (is replaced), the nmethod
// must be recompiled. No other dependencies are implied.
evol_method,
FIRST_TYPE = evol_method,
// A context type CX is a leaf it if has no proper subtype.
leaf_type,
// An abstract class CX has exactly one concrete subtype CC.
abstract_with_unique_concrete_subtype,
// The type CX is purely abstract, with no concrete subtype* at all.
abstract_with_no_concrete_subtype,
// The concrete CX is free of concrete proper subtypes.
concrete_with_no_concrete_subtype,
// Given a method M1 and a context class CX, the set MM(CX, M1) of
// "concrete matching methods" in CX of M1 is the set of every
// concrete M2 for which it is possible to create an invokevirtual
// or invokeinterface call site that can reach either M1 or M2.
// That is, M1 and M2 share a name, signature, and vtable index.
// We wish to notice when the set MM(CX, M1) is just {M1}, or
// perhaps a set of two {M1,M2}, and issue dependencies on this.
// The set MM(CX, M1) can be computed by starting with any matching
// concrete M2 that is inherited into CX, and then walking the
// subtypes* of CX looking for concrete definitions.
// The parameters to this dependency are the method M1 and the
// context class CX. M1 must be either inherited in CX or defined
// in a subtype* of CX. It asserts that MM(CX, M1) is no greater
// than {M1}.
unique_concrete_method, // one unique concrete method under CX
// An "exclusive" assertion concerns two methods or subtypes, and
// declares that there are at most two (or perhaps later N>2)
// specific items that jointly satisfy the restriction.
// We list all items explicitly rather than just giving their
// count, for robustness in the face of complex schema changes.
// A context class CX (which may be either abstract or concrete)
// has two exclusive concrete subtypes* C1, C2 if every concrete
// subtype* of CX is either C1 or C2. Note that if neither C1 or C2
// are equal to CX, then CX itself must be abstract. But it is
// also possible (for example) that C1 is CX (a concrete class)
// and C2 is a proper subtype of C1.
abstract_with_exclusive_concrete_subtypes_2,
// This dependency asserts that MM(CX, M1) is no greater than {M1,M2}.
exclusive_concrete_methods_2,
// This dependency asserts that no instances of class or it's
// subclasses require finalization registration.
no_finalizable_subclasses,
TYPE_LIMIT
};
enum {
LG2_TYPE_LIMIT = 4, // assert(TYPE_LIMIT <= (1<<LG2_TYPE_LIMIT))
// handy categorizations of dependency types:
all_types = ((1<<TYPE_LIMIT)-1) & ((-1)<<FIRST_TYPE),
non_ctxk_types = (1<<evol_method),
ctxk_types = all_types & ~non_ctxk_types,
max_arg_count = 3, // current maximum number of arguments (incl. ctxk)
// A "context type" is a class or interface that
// provides context for evaluating a dependency.
// When present, it is one of the arguments (dep_context_arg).
//
// If a dependency does not have a context type, there is a
// default context, depending on the type of the dependency.
// This bit signals that a default context has been compressed away.
default_context_type_bit = (1<<LG2_TYPE_LIMIT)
};
static const char* dep_name(DepType dept);
static int dep_args(DepType dept);
static int dep_context_arg(DepType dept) {
return dept_in_mask(dept, ctxk_types)? 0: -1;
}
private:
// State for writing a new set of dependencies:
GrowableArray<int>* _dep_seen; // (seen[h->ident] & (1<<dept))
GrowableArray<ciObject*>* _deps[TYPE_LIMIT];
static const char* _dep_name[TYPE_LIMIT];
static int _dep_args[TYPE_LIMIT];
static bool dept_in_mask(DepType dept, int mask) {
return (int)dept >= 0 && dept < TYPE_LIMIT && ((1<<dept) & mask) != 0;
}
bool note_dep_seen(int dept, ciObject* x) {
assert(dept < BitsPerInt, "oob");
int x_id = x->ident();
assert(_dep_seen != NULL, "deps must be writable");
int seen = _dep_seen->at_grow(x_id, 0);
_dep_seen->at_put(x_id, seen | (1<<dept));
// return true if we've already seen dept/x
return (seen & (1<<dept)) != 0;
}
bool maybe_merge_ctxk(GrowableArray<ciObject*>* deps,
int ctxk_i, ciKlass* ctxk);
void sort_all_deps();
size_t estimate_size_in_bytes();
// Initialize _deps, etc.
void initialize(ciEnv* env);
// State for making a new set of dependencies:
OopRecorder* _oop_recorder;
// Logging support
CompileLog* _log;
address _content_bytes; // everything but the oop references, encoded
size_t _size_in_bytes;
public:
// Make a new empty dependencies set.
Dependencies(ciEnv* env) {
initialize(env);
}
private:
// Check for a valid context type.
// Enforce the restriction against array types.
static void check_ctxk(ciKlass* ctxk) {
assert(ctxk->is_instance_klass(), "java types only");
}
static void check_ctxk_concrete(ciKlass* ctxk) {
assert(is_concrete_klass(ctxk->as_instance_klass()), "must be concrete");
}
static void check_ctxk_abstract(ciKlass* ctxk) {
check_ctxk(ctxk);
assert(!is_concrete_klass(ctxk->as_instance_klass()), "must be abstract");
}
void assert_common_1(DepType dept, ciObject* x);
void assert_common_2(DepType dept, ciKlass* ctxk, ciObject* x);
void assert_common_3(DepType dept, ciKlass* ctxk, ciObject* x, ciObject* x2);
public:
// Adding assertions to a new dependency set at compile time:
void assert_evol_method(ciMethod* m);
void assert_leaf_type(ciKlass* ctxk);
void assert_abstract_with_unique_concrete_subtype(ciKlass* ctxk, ciKlass* conck);
void assert_abstract_with_no_concrete_subtype(ciKlass* ctxk);
void assert_concrete_with_no_concrete_subtype(ciKlass* ctxk);
void assert_unique_concrete_method(ciKlass* ctxk, ciMethod* uniqm);
void assert_abstract_with_exclusive_concrete_subtypes(ciKlass* ctxk, ciKlass* k1, ciKlass* k2);
void assert_exclusive_concrete_methods(ciKlass* ctxk, ciMethod* m1, ciMethod* m2);
void assert_has_no_finalizable_subclasses(ciKlass* ctxk);
// Define whether a given method or type is concrete.
// These methods define the term "concrete" as used in this module.
// For this module, an "abstract" class is one which is non-concrete.
//
// Future optimizations may allow some classes to remain
// non-concrete until their first instantiation, and allow some
// methods to remain non-concrete until their first invocation.
// In that case, there would be a middle ground between concrete
// and abstract (as defined by the Java language and VM).
static bool is_concrete_klass(klassOop k); // k is instantiable
static bool is_concrete_method(methodOop m); // m is invocable
static Klass* find_finalizable_subclass(Klass* k);
// These versions of the concreteness queries work through the CI.
// The CI versions are allowed to skew sometimes from the VM
// (oop-based) versions. The cost of such a difference is a
// (safely) aborted compilation, or a deoptimization, or a missed
// optimization opportunity.
//
// In order to prevent spurious assertions, query results must
// remain stable within any single ciEnv instance. (I.e., they must
// not go back into the VM to get their value; they must cache the
// bit in the CI, either eagerly or lazily.)
static bool is_concrete_klass(ciInstanceKlass* k); // k appears instantiable
static bool is_concrete_method(ciMethod* m); // m appears invocable
static bool has_finalizable_subclass(ciInstanceKlass* k);
// As a general rule, it is OK to compile under the assumption that
// a given type or method is concrete, even if it at some future
// point becomes abstract. So dependency checking is one-sided, in
// that it permits supposedly concrete classes or methods to turn up
// as really abstract. (This shouldn't happen, except during class
// evolution, but that's the logic of the checking.) However, if a
// supposedly abstract class or method suddenly becomes concrete, a
// dependency on it must fail.
// Checking old assertions at run-time (in the VM only):
static klassOop check_evol_method(methodOop m);
static klassOop check_leaf_type(klassOop ctxk);
static klassOop check_abstract_with_unique_concrete_subtype(klassOop ctxk, klassOop conck,
DepChange* changes = NULL);
static klassOop check_abstract_with_no_concrete_subtype(klassOop ctxk,
DepChange* changes = NULL);
static klassOop check_concrete_with_no_concrete_subtype(klassOop ctxk,
DepChange* changes = NULL);
static klassOop check_unique_concrete_method(klassOop ctxk, methodOop uniqm,
DepChange* changes = NULL);
static klassOop check_abstract_with_exclusive_concrete_subtypes(klassOop ctxk, klassOop k1, klassOop k2,
DepChange* changes = NULL);
static klassOop check_exclusive_concrete_methods(klassOop ctxk, methodOop m1, methodOop m2,
DepChange* changes = NULL);
static klassOop check_has_no_finalizable_subclasses(klassOop ctxk,
DepChange* changes = NULL);
// A returned klassOop is NULL if the dependency assertion is still
// valid. A non-NULL klassOop is a 'witness' to the assertion
// failure, a point in the class hierarchy where the assertion has
// been proven false. For example, if check_leaf_type returns
// non-NULL, the value is a subtype of the supposed leaf type. This
// witness value may be useful for logging the dependency failure.
// Note that, when a dependency fails, there may be several possible
// witnesses to the failure. The value returned from the check_foo
// method is chosen arbitrarily.
// The 'changes' value, if non-null, requests a limited spot-check
// near the indicated recent changes in the class hierarchy.
// It is used by DepStream::spot_check_dependency_at.
// Detecting possible new assertions:
static klassOop find_unique_concrete_subtype(klassOop ctxk);
static methodOop find_unique_concrete_method(klassOop ctxk, methodOop m);
static int find_exclusive_concrete_subtypes(klassOop ctxk, int klen, klassOop k[]);
static int find_exclusive_concrete_methods(klassOop ctxk, int mlen, methodOop m[]);
// Create the encoding which will be stored in an nmethod.
void encode_content_bytes();
address content_bytes() {
assert(_content_bytes != NULL, "encode it first");
return _content_bytes;
}
size_t size_in_bytes() {
assert(_content_bytes != NULL, "encode it first");
return _size_in_bytes;
}
OopRecorder* oop_recorder() { return _oop_recorder; }
CompileLog* log() { return _log; }
void copy_to(nmethod* nm);
void log_all_dependencies();
void log_dependency(DepType dept, int nargs, ciObject* args[]) {
write_dependency_to(log(), dept, nargs, args);
}
void log_dependency(DepType dept,
ciObject* x0,
ciObject* x1 = NULL,
ciObject* x2 = NULL) {
if (log() == NULL) return;
ciObject* args[max_arg_count];
args[0] = x0;
args[1] = x1;
args[2] = x2;
assert(2 < max_arg_count, "");
log_dependency(dept, dep_args(dept), args);
}
static void write_dependency_to(CompileLog* log,
DepType dept,
int nargs, ciObject* args[],
klassOop witness = NULL);
static void write_dependency_to(CompileLog* log,
DepType dept,
int nargs, oop args[],
klassOop witness = NULL);
static void write_dependency_to(xmlStream* xtty,
DepType dept,
int nargs, oop args[],
klassOop witness = NULL);
static void print_dependency(DepType dept,
int nargs, oop args[],
klassOop witness = NULL);
private:
// helper for encoding common context types as zero:
static ciKlass* ctxk_encoded_as_null(DepType dept, ciObject* x);
static klassOop ctxk_encoded_as_null(DepType dept, oop x);
public:
// Use this to iterate over an nmethod's dependency set.
// Works on new and old dependency sets.
// Usage:
//
// ;
// Dependencies::DepType dept;
// for (Dependencies::DepStream deps(nm); deps.next(); ) {
// ...
// }
//
// The caller must be in the VM, since oops are not wrapped in handles.
class DepStream {
private:
nmethod* _code; // null if in a compiler thread
Dependencies* _deps; // null if not in a compiler thread
CompressedReadStream _bytes;
#ifdef ASSERT
size_t _byte_limit;
#endif
// iteration variables:
DepType _type;
int _xi[max_arg_count+1];
void initial_asserts(size_t byte_limit) NOT_DEBUG({});
inline oop recorded_oop_at(int i);
// => _code? _code->oop_at(i): *_deps->_oop_recorder->handle_at(i)
klassOop check_dependency_impl(DepChange* changes);
public:
DepStream(Dependencies* deps)
: _deps(deps),
_code(NULL),
_bytes(deps->content_bytes())
{
initial_asserts(deps->size_in_bytes());
}
DepStream(nmethod* code)
: _deps(NULL),
_code(code),
_bytes(code->dependencies_begin())
{
initial_asserts(code->dependencies_size());
}
bool next();
DepType type() { return _type; }
int argument_count() { return dep_args(type()); }
int argument_index(int i) { assert(0 <= i && i < argument_count(), "oob");
return _xi[i]; }
oop argument(int i); // => recorded_oop_at(argument_index(i))
klassOop context_type();
methodOop method_argument(int i) {
oop x = argument(i);
assert(x->is_method(), "type");
return (methodOop) x;
}
klassOop type_argument(int i) {
oop x = argument(i);
assert(x->is_klass(), "type");
return (klassOop) x;
}
// The point of the whole exercise: Is this dep is still OK?
klassOop check_dependency() {
return check_dependency_impl(NULL);
}
// A lighter version: Checks only around recent changes in a class
// hierarchy. (See Universe::flush_dependents_on.)
klassOop spot_check_dependency_at(DepChange& changes);
// Log the current dependency to xtty or compilation log.
void log_dependency(klassOop witness = NULL);
// Print the current dependency to tty.
void print_dependency(klassOop witness = NULL, bool verbose = false);
};
friend class Dependencies::DepStream;
static void print_statistics() PRODUCT_RETURN;
};
// A class hierarchy change coming through the VM (under the Compile_lock).
// The change is structured as a single new type with any number of supers
// and implemented interface types. Other than the new type, any of the
// super types can be context types for a relevant dependency, which the
// new type could invalidate.
class DepChange : public StackObj {
private:
enum ChangeType {
NO_CHANGE = 0, // an uninvolved klass
Change_new_type, // a newly loaded type
Change_new_sub, // a super with a new subtype
Change_new_impl, // an interface with a new implementation
CHANGE_LIMIT,
Start_Klass = CHANGE_LIMIT // internal indicator for ContextStream
};
// each change set is rooted in exactly one new type (at present):
KlassHandle _new_type;
void initialize();
public:
// notes the new type, marks it and all its super-types
DepChange(KlassHandle new_type)
: _new_type(new_type)
{
initialize();
}
// cleans up the marks
~DepChange();
klassOop new_type() { return _new_type(); }
// involves_context(k) is true if k is new_type or any of the super types
bool involves_context(klassOop k);
// Usage:
// for (DepChange::ContextStream str(changes); str.next(); ) {
// klassOop k = str.klass();
// switch (str.change_type()) {
// ...
// }
// }
class ContextStream : public StackObj {
private:
DepChange& _changes;
friend class DepChange;
// iteration variables:
ChangeType _change_type;
klassOop _klass;
objArrayOop _ti_base; // i.e., transitive_interfaces
int _ti_index;
int _ti_limit;
// start at the beginning:
void start() {
klassOop new_type = _changes.new_type();
_change_type = (new_type == NULL ? NO_CHANGE: Start_Klass);
_klass = new_type;
_ti_base = NULL;
_ti_index = 0;
_ti_limit = 0;
}
ContextStream(DepChange& changes)
: _changes(changes)
{ start(); }
public:
ContextStream(DepChange& changes, No_Safepoint_Verifier& nsv)
: _changes(changes)
// the nsv argument makes it safe to hold oops like _klass
{ start(); }
bool next();
klassOop klass() { return _klass; }
};
friend class DepChange::ContextStream;
void print();
};