oopMapCache.cpp

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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#include"interpreter/bytecodeStream.hpp"
#include"interpreter/oopMapCache.hpp"
#include"logging/log.hpp"
#include"logging/logStream.hpp"
#include"memory/allocation.inline.hpp"
#include"memory/resourceArea.hpp"
#include"oops/generateOopMap.hpp"
#include"oops/oop.inline.hpp"
#include"runtime/atomic.hpp"
#include"runtime/handles.inline.hpp"
#include"runtime/safepoint.hpp"
#include"runtime/signature.hpp"
#include"utilities/globalCounter.inline.hpp"

classOopMapCacheEntry: privateInterpreterOopMap {
friendclassInterpreterOopMap;
friendclassOopMapForCacheEntry;
friendclassOopMapCache;
friendclassVerifyClosure;

private:
 OopMapCacheEntry* _next;

protected:
// Initialization
voidfill(const methodHandle& method, int bci);
// fills the bit mask for native calls
voidfill_for_native(const methodHandle& method);
voidset_mask(CellTypeState* vars, CellTypeState* stack, int stack_top);

// Deallocate bit masks and initialize fields
voidflush();

staticvoiddeallocate(OopMapCacheEntry* const entry);

private:
voidallocate_bit_mask(); // allocates the bit mask on C heap f necessary
voiddeallocate_bit_mask(); // allocates the bit mask on C heap f necessary
boolverify_mask(CellTypeState *vars, CellTypeState *stack, int max_locals, int stack_top);

public:
OopMapCacheEntry() : InterpreterOopMap() {
 _next = nullptr;
 }
};


// Implementation of OopMapForCacheEntry
// (subclass of GenerateOopMap, initializes an OopMapCacheEntry for a given method and bci)

classOopMapForCacheEntry: publicGenerateOopMap {
 OopMapCacheEntry *_entry;
int _bci;
int _stack_top;

virtualboolreport_results() const { returnfalse; }
virtualboolpossible_gc_point (BytecodeStream *bcs);
virtualvoidfill_stackmap_prolog (int nof_gc_points);
virtualvoidfill_stackmap_epilog ();
virtualvoidfill_stackmap_for_opcodes (BytecodeStream *bcs,
 CellTypeState* vars,
 CellTypeState* stack,
int stack_top);
virtualvoidfill_init_vars (GrowableArray<intptr_t> *init_vars);

public:
OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry *entry);

// Computes stack map for (method,bci) and initialize entry
boolcompute_map(Thread* current);
intsize();
};


OopMapForCacheEntry::OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry* entry) : GenerateOopMap(method) {
 _bci = bci;
 _entry = entry;
 _stack_top = -1;
}


boolOopMapForCacheEntry::compute_map(Thread* current) {
assert(!method()->is_native(), "cannot compute oop map for native methods");
// First check if it is a method where the stackmap is always empty
if (method()->code_size() == 0 || method()->max_locals() + method()->max_stack() == 0) {
 _entry->set_mask_size(0);
 } else {
 ResourceMark rm;
if (!GenerateOopMap::compute_map(current)) {
fatal("Unrecoverable verification or out-of-memory error");
returnfalse;
 }
result_for_basicblock(_bci);
 }
returntrue;
}


boolOopMapForCacheEntry::possible_gc_point(BytecodeStream *bcs) {
returnfalse; // We are not reporting any result. We call result_for_basicblock directly
}


voidOopMapForCacheEntry::fill_stackmap_prolog(int nof_gc_points) {
// Do nothing
}


voidOopMapForCacheEntry::fill_stackmap_epilog() {
// Do nothing
}


voidOopMapForCacheEntry::fill_init_vars(GrowableArray<intptr_t> *init_vars) {
// Do nothing
}


voidOopMapForCacheEntry::fill_stackmap_for_opcodes(BytecodeStream *bcs,
 CellTypeState* vars,
 CellTypeState* stack,
int stack_top) {
// Only interested in one specific bci
if (bcs->bci() == _bci) {
 _entry->set_mask(vars, stack, stack_top);
 _stack_top = stack_top;
 }
}


intOopMapForCacheEntry::size() {
assert(_stack_top != -1, "compute_map must be called first");
return ((method()->is_static()) ? 0 : 1) + method()->max_locals() + _stack_top;
}


// Implementation of InterpreterOopMap and OopMapCacheEntry

classVerifyClosure : publicOffsetClosure {
private:
 OopMapCacheEntry* _entry;
bool _failed;

public:
VerifyClosure(OopMapCacheEntry* entry) { _entry = entry; _failed = false; }
voidoffset_do(int offset) { if (!_entry->is_oop(offset)) _failed = true; }
boolfailed() const { return _failed; }
};

InterpreterOopMap::InterpreterOopMap() {
initialize();
}

InterpreterOopMap::~InterpreterOopMap() {
if (has_valid_mask() && mask_size() > small_mask_limit) {
assert(_bit_mask[0] != 0, "should have pointer to C heap");
FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
 }
}

boolInterpreterOopMap::is_empty() const {
bool result = _method == nullptr;
assert(_method != nullptr || (_bci == 0 &&
 (_mask_size == 0 || _mask_size == USHRT_MAX) &&
 _bit_mask[0] == 0), "Should be completely empty");
return result;
}

voidInterpreterOopMap::initialize() {
 _method = nullptr;
 _mask_size = USHRT_MAX; // This value should cause a failure quickly
 _bci = 0;
 _expression_stack_size = 0;
 _num_oops = 0;
for (int i = 0; i < N; i++) _bit_mask[i] = 0;
}

voidInterpreterOopMap::iterate_oop(OffsetClosure* oop_closure) const {
int n = number_of_entries();
int word_index = 0;
uintptr_t value = 0;
uintptr_t mask = 0;
// iterate over entries
for (int i = 0; i < n; i++, mask <<= bits_per_entry) {
// get current word
if (mask == 0) {
 value = bit_mask()[word_index++];
 mask = 1;
 }
// test for oop
if ((value & (mask << oop_bit_number)) != 0) oop_closure->offset_do(i);
 }
}

voidInterpreterOopMap::print() const {
int n = number_of_entries();
 tty->print("oop map for ");
method()->print_value();
 tty->print(" @ %d = [%d] { ", bci(), n);
for (int i = 0; i < n; i++) {
if (is_dead(i)) tty->print("%d+ ", i);
else
if (is_oop(i)) tty->print("%d ", i);
 }
 tty->print_cr("}");
}

classMaskFillerForNative: publicNativeSignatureIterator {
private:
uintptr_t * _mask; // the bit mask to be filled
int _size; // the mask size in bits
int _num_oops;

voidset_one(int i) {
 _num_oops++;
 i *= InterpreterOopMap::bits_per_entry;
assert(0 <= i && i < _size, "offset out of bounds");
 _mask[i / BitsPerWord] |= (((uintptr_t) 1 << InterpreterOopMap::oop_bit_number) << (i % BitsPerWord));
 }

public:
voidpass_byte() { /* ignore */ }
voidpass_short() { /* ignore */ }
voidpass_int() { /* ignore */ }
voidpass_long() { /* ignore */ }
voidpass_float() { /* ignore */ }
voidpass_double() { /* ignore */ }
voidpass_object() { set_one(offset()); }

MaskFillerForNative(const methodHandle& method, uintptr_t* mask, int size) : NativeSignatureIterator(method) {
 _mask = mask;
 _size = size;
 _num_oops = 0;
// initialize with 0
int i = (size + BitsPerWord - 1) / BitsPerWord;
while (i-- > 0) _mask[i] = 0;
 }

voidgenerate() {
 iterate();
 }

intnum_oops() { return _num_oops; }
};

boolOopMapCacheEntry::verify_mask(CellTypeState* vars, CellTypeState* stack, int max_locals, int stack_top) {
// Check mask includes map
 VerifyClosure blk(this);
iterate_oop(&blk);
if (blk.failed()) returnfalse;

// Check if map is generated correctly
// (Use ?: operator to make sure all 'true' & 'false' are represented exactly the same so we can use == afterwards)
constboollog = log_is_enabled(Trace, interpreter, oopmap);
 LogStream st(Log(interpreter, oopmap)::trace());

if (log) st.print("Locals (%d): ", max_locals);
for(int i = 0; i < max_locals; i++) {
bool v1 = is_oop(i) ? true : false;
bool v2 = vars[i].is_reference() ? true : false;
assert(v1 == v2, "locals oop mask generation error");
if (log) st.print("%d", v1 ? 1 : 0);
 }
if (log) st.cr();

if (log) st.print("Stack (%d): ", stack_top);
for(int j = 0; j < stack_top; j++) {
bool v1 = is_oop(max_locals + j) ? true : false;
bool v2 = stack[j].is_reference() ? true : false;
assert(v1 == v2, "stack oop mask generation error");
if (log) st.print("%d", v1 ? 1 : 0);
 }
if (log) st.cr();
returntrue;
}

voidOopMapCacheEntry::allocate_bit_mask() {
if (mask_size() > small_mask_limit) {
assert(_bit_mask[0] == 0, "bit mask should be new or just flushed");
 _bit_mask[0] = (intptr_t)
NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
 }
}

voidOopMapCacheEntry::deallocate_bit_mask() {
if (mask_size() > small_mask_limit && _bit_mask[0] != 0) {
assert(!Thread::current()->resource_area()->contains((void*)_bit_mask[0]),
"This bit mask should not be in the resource area");
FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
DEBUG_ONLY(_bit_mask[0] = 0;)
 }
}


voidOopMapCacheEntry::fill_for_native(const methodHandle& mh) {
assert(mh->is_native(), "method must be native method");
set_mask_size(mh->size_of_parameters() * bits_per_entry);
allocate_bit_mask();
// fill mask for parameters
 MaskFillerForNative mf(mh, bit_mask(), mask_size());
 mf.generate();
 _num_oops = mf.num_oops();
}


voidOopMapCacheEntry::fill(const methodHandle& method, int bci) {
// Flush entry to deallocate an existing entry
flush();
set_method(method());
set_bci(checked_cast<unsignedshort>(bci)); // bci is always u2
if (method->is_native()) {
// Native method activations have oops only among the parameters and one
// extra oop following the parameters (the mirror for static native methods).
fill_for_native(method);
 } else {
 OopMapForCacheEntry gen(method, bci, this);
if (!gen.compute_map(Thread::current())) {
fatal("Unrecoverable verification or out-of-memory error");
 }
 }
}


voidOopMapCacheEntry::set_mask(CellTypeState *vars, CellTypeState *stack, int stack_top) {
// compute bit mask size
int max_locals = method()->max_locals();
int n_entries = max_locals + stack_top;
set_mask_size(n_entries * bits_per_entry);
allocate_bit_mask();
set_expression_stack_size(stack_top);

// compute bits
int word_index = 0;
uintptr_t value = 0;
uintptr_t mask = 1;

 _num_oops = 0;
 CellTypeState* cell = vars;
for (int entry_index = 0; entry_index < n_entries; entry_index++, mask <<= bits_per_entry, cell++) {
// store last word
if (mask == 0) {
bit_mask()[word_index++] = value;
 value = 0;
 mask = 1;
 }

// switch to stack when done with locals
if (entry_index == max_locals) {
 cell = stack;
 }

// set oop bit
if ( cell->is_reference()) {
 value |= (mask << oop_bit_number );
 _num_oops++;
 }

// set dead bit
if (!cell->is_live()) {
 value |= (mask << dead_bit_number);
assert(!cell->is_reference(), "dead value marked as oop");
 }
 }

// make sure last word is stored
bit_mask()[word_index] = value;

// verify bit mask
assert(verify_mask(vars, stack, max_locals, stack_top), "mask could not be verified");
}

voidOopMapCacheEntry::flush() {
deallocate_bit_mask();
initialize();
}

voidOopMapCacheEntry::deallocate(OopMapCacheEntry* const entry) {
 entry->flush();
FREE_C_HEAP_OBJ(entry);
}

// Implementation of OopMapCache

voidInterpreterOopMap::copy_from(const OopMapCacheEntry* src) {
// The expectation is that this InterpreterOopMap is recently created
// and empty. It is used to get a copy of a cached entry.
assert(!has_valid_mask(), "InterpreterOopMap object can only be filled once");
assert(src->has_valid_mask(), "Cannot copy entry with an invalid mask");

set_method(src->method());
set_bci(src->bci());
set_mask_size(src->mask_size());
set_expression_stack_size(src->expression_stack_size());
 _num_oops = src->num_oops();

// Is the bit mask contained in the entry?
if (src->mask_size() <= small_mask_limit) {
memcpy(_bit_mask, src->_bit_mask, mask_word_size() * BytesPerWord);
 } else {
 _bit_mask[0] = (uintptr_t) NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
memcpy((void*) _bit_mask[0], (void*) src->_bit_mask[0], mask_word_size() * BytesPerWord);
 }
}

inlineunsignedintOopMapCache::hash_value_for(const methodHandle& method, int bci) const {
// We use method->code_size() rather than method->identity_hash() below since
// the mark may not be present if a pointer to the method is already reversed.
return ((unsignedint) bci)
 ^ ((unsignedint) method->max_locals() << 2)
 ^ ((unsignedint) method->code_size() << 4)
 ^ ((unsignedint) method->size_of_parameters() << 6);
}

OopMapCacheEntry* volatile OopMapCache::_old_entries = nullptr;

OopMapCache::OopMapCache() {
for(int i = 0; i < size; i++) _array[i] = nullptr;
}


OopMapCache::~OopMapCache() {
// Deallocate oop maps that are allocated out-of-line
flush();
}

OopMapCacheEntry* OopMapCache::entry_at(int i) const {
returnAtomic::load_acquire(&(_array[i % size]));
}

boolOopMapCache::put_at(int i, OopMapCacheEntry* entry, OopMapCacheEntry* old) {
returnAtomic::cmpxchg(&_array[i % size], old, entry) == old;
}

voidOopMapCache::flush() {
for (int i = 0; i < size; i++) {
 OopMapCacheEntry* entry = _array[i];
if (entry != nullptr) {
 _array[i] = nullptr; // no barrier, only called in OopMapCache destructor
OopMapCacheEntry::deallocate(entry);
 }
 }
}

voidOopMapCache::flush_obsolete_entries() {
assert(SafepointSynchronize::is_at_safepoint(), "called by RedefineClasses in a safepoint");
for (int i = 0; i < size; i++) {
 OopMapCacheEntry* entry = _array[i];
if (entry != nullptr && !entry->is_empty() && entry->method()->is_old()) {
// Cache entry is occupied by an old redefined method and we don't want
// to pin it down so flush the entry.
if (log_is_enabled(Debug, redefine, class, oopmap)) {
 ResourceMark rm;
log_debug(redefine, class, interpreter, oopmap)
 ("flush: %s(%s): cached entry @%d",
 entry->method()->name()->as_C_string(), entry->method()->signature()->as_C_string(), i);
 }
 _array[i] = nullptr;
OopMapCacheEntry::deallocate(entry);
 }
 }
}

// Lookup or compute/cache the entry.
voidOopMapCache::lookup(const methodHandle& method,
int bci,
 InterpreterOopMap* entry_for) {
int probe = hash_value_for(method, bci);

if (log_is_enabled(Debug, interpreter, oopmap)) {
staticint count = 0;
 ResourceMark rm;
log_debug(interpreter, oopmap)
 ("%d - Computing oopmap at bci %d for %s at hash %d", ++count, bci,
method()->name_and_sig_as_C_string(), probe);
 }

// Search hashtable for match.
// Need a critical section to avoid race against concurrent reclamation.
 {
 GlobalCounter::CriticalSection cs(Thread::current());
for (int i = 0; i < probe_depth; i++) {
 OopMapCacheEntry *entry = entry_at(probe + i);
if (entry != nullptr && !entry->is_empty() && entry->match(method, bci)) {
 entry_for->copy_from(entry);
assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
log_debug(interpreter, oopmap)("- found at hash %d", probe + i);
return;
 }
 }
 }

// Entry is not in hashtable.
// Compute entry

 OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
 tmp->initialize();
 tmp->fill(method, bci);
 entry_for->copy_from(tmp);

if (method->should_not_be_cached()) {
// It is either not safe or not a good idea to cache this Method*
// at this time. We give the caller of lookup() a copy of the
// interesting info via parameter entry_for, but we don't add it to
// the cache. See the gory details in Method*.cpp.
OopMapCacheEntry::deallocate(tmp);
return;
 }

// First search for an empty slot
for (int i = 0; i < probe_depth; i++) {
 OopMapCacheEntry* entry = entry_at(probe + i);
if (entry == nullptr) {
if (put_at(probe + i, tmp, nullptr)) {
assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
return;
 }
 }
 }

log_debug(interpreter, oopmap)("*** collision in oopmap cache - flushing item ***");

// No empty slot (uncommon case). Use (some approximation of a) LRU algorithm
// where the first entry in the collision array is replaced with the new one.
 OopMapCacheEntry* old = entry_at(probe + 0);
if (put_at(probe + 0, tmp, old)) {
// Cannot deallocate old entry on the spot: it can still be used by readers
// that got a reference to it before we were able to replace it in the map.
// Instead of synchronizing on GlobalCounter here and incurring heavy thread
// walk, we do this clean up out of band.
enqueue_for_cleanup(old);
 } else {
OopMapCacheEntry::deallocate(tmp);
 }

assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
return;
}

voidOopMapCache::enqueue_for_cleanup(OopMapCacheEntry* entry) {
while (true) {
 OopMapCacheEntry* head = Atomic::load(&_old_entries);
 entry->_next = head;
if (Atomic::cmpxchg(&_old_entries, head, entry) == head) {
// Enqueued successfully.
break;
 }
 }

if (log_is_enabled(Debug, interpreter, oopmap)) {
 ResourceMark rm;
log_debug(interpreter, oopmap)("enqueue %s at bci %d for cleanup",
 entry->method()->name_and_sig_as_C_string(), entry->bci());
 }
}

boolOopMapCache::has_cleanup_work() {
returnAtomic::load(&_old_entries) != nullptr;
}

voidOopMapCache::try_trigger_cleanup() {
// See we can take the lock for the notification without blocking.
// This allows triggering the cleanup from GC paths, that can hold
// the service lock for e.g. oop iteration in service thread.
if (has_cleanup_work() && Service_lock->try_lock_without_rank_check()) {
 Service_lock->notify_all();
 Service_lock->unlock();
 }
}

voidOopMapCache::cleanup() {
 OopMapCacheEntry* entry = Atomic::xchg(&_old_entries, (OopMapCacheEntry*)nullptr);
if (entry == nullptr) {
// No work.
return;
 }

// About to delete the entries than might still be accessed by other threads
// on lookup path. Need to sync up with them before proceeding.
GlobalCounter::write_synchronize();

while (entry != nullptr) {
if (log_is_enabled(Debug, interpreter, oopmap)) {
 ResourceMark rm;
log_debug(interpreter, oopmap)("cleanup entry %s at bci %d",
 entry->method()->name_and_sig_as_C_string(), entry->bci());
 }
 OopMapCacheEntry* next = entry->_next;
OopMapCacheEntry::deallocate(entry);
 entry = next;
 }
}

voidOopMapCache::compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry) {
// Due to the invariants above it's tricky to allocate a temporary OopMapCacheEntry on the stack
 OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
 tmp->initialize();
 tmp->fill(method, bci);
if (tmp->has_valid_mask()) {
 entry->copy_from(tmp);
 }
OopMapCacheEntry::deallocate(tmp);
}