Files
sdk/runtime/vm/code_descriptors.cc
T
Aske Simon Christensen cec963f028 The current growth strategy for growable arrays allocates a backing array of size 2 at (empty) creation and doubles the size whenever the capacity is insufficient while adding elements.
I collected statistics for the sizes and capacities of growable arrays which are promoted to old-space or survive an old-space gc when running dart2js and Fasta. For these applications, the vast majority of arrays stay empty. More than half of the total object size of promoted backing arrays is backing for empty growable arrays.

Furthermore, since the overhead for an array is 3 words (header, type parameters and length), and object sizes are rounded up to an even number of words, we waste one word for all even-sized arrays.

This CL changes the growth strategy so that empty growable arrays are created with a shared, zero-sized array as backing, avoiding the allocation of a backing array if no elements are added. When the array needs to grow, it starts out at 3 and grows to double size plus one each time: 7, 15, 31, ...

A few places in the VM code need to handle these shared, zero-sized arrays specially. In particular, the Array::MakeArray function needs to allocate a new, empty array if its result is to be returned to Dart code.

Benchmarks suggest that the change improves memory usage by a few percent overall and does not significantly affect run time.

BUG=
R=erikcorry@google.com

Review-Url: https://codereview.chromium.org/2949803002 .
2017-06-22 10:51:54 +02:00

658 lines
20 KiB
C++

// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "vm/code_descriptors.h"
#include "vm/log.h"
namespace dart {
void DescriptorList::AddDescriptor(RawPcDescriptors::Kind kind,
intptr_t pc_offset,
intptr_t deopt_id,
TokenPosition token_pos,
intptr_t try_index) {
ASSERT((kind == RawPcDescriptors::kRuntimeCall) ||
(kind == RawPcDescriptors::kOther) ||
(deopt_id != Thread::kNoDeoptId));
// When precompiling, we only use pc descriptors for exceptions.
if (!FLAG_precompiled_mode || try_index != -1) {
intptr_t merged_kind_try =
RawPcDescriptors::MergedKindTry::Encode(kind, try_index);
PcDescriptors::EncodeInteger(&encoded_data_, merged_kind_try);
PcDescriptors::EncodeInteger(&encoded_data_, pc_offset - prev_pc_offset);
PcDescriptors::EncodeInteger(&encoded_data_, deopt_id - prev_deopt_id);
PcDescriptors::EncodeInteger(&encoded_data_,
token_pos.value() - prev_token_pos);
prev_pc_offset = pc_offset;
prev_deopt_id = deopt_id;
prev_token_pos = token_pos.value();
}
}
RawPcDescriptors* DescriptorList::FinalizePcDescriptors(uword entry_point) {
if (encoded_data_.length() == 0) {
return Object::empty_descriptors().raw();
}
return PcDescriptors::New(&encoded_data_);
}
void StackMapTableBuilder::AddEntry(intptr_t pc_offset,
BitmapBuilder* bitmap,
intptr_t register_bit_count) {
stack_map_ = StackMap::New(pc_offset, bitmap, register_bit_count);
list_.Add(stack_map_, Heap::kOld);
}
bool StackMapTableBuilder::Verify() {
intptr_t num_entries = Length();
StackMap& map1 = StackMap::Handle();
StackMap& map2 = StackMap::Handle();
for (intptr_t i = 1; i < num_entries; i++) {
map1 = MapAt(i - 1);
map2 = MapAt(i);
// Ensure there are no duplicates and the entries are sorted.
if (map1.PcOffset() >= map2.PcOffset()) {
return false;
}
}
return true;
}
RawArray* StackMapTableBuilder::FinalizeStackMaps(const Code& code) {
ASSERT(Verify());
intptr_t num_entries = Length();
if (num_entries == 0) {
return Object::empty_array().raw();
}
return Array::MakeFixedLength(list_);
}
RawStackMap* StackMapTableBuilder::MapAt(intptr_t index) const {
StackMap& map = StackMap::Handle();
map ^= list_.At(index);
return map.raw();
}
RawExceptionHandlers* ExceptionHandlerList::FinalizeExceptionHandlers(
uword entry_point) const {
intptr_t num_handlers = Length();
if (num_handlers == 0) {
return Object::empty_exception_handlers().raw();
}
const ExceptionHandlers& handlers =
ExceptionHandlers::Handle(ExceptionHandlers::New(num_handlers));
for (intptr_t i = 0; i < num_handlers; i++) {
// Assert that every element in the array has been initialized.
if (list_[i].handler_types == NULL) {
// Unreachable handler, entry not computed.
// Initialize it to some meaningful value.
const bool has_catch_all = false;
// Check it is uninitialized.
ASSERT((list_[i].outer_try_index == -1) &&
(list_[i].pc_offset == ExceptionHandlers::kInvalidPcOffset));
handlers.SetHandlerInfo(i, list_[i].outer_try_index, list_[i].pc_offset,
list_[i].needs_stacktrace, has_catch_all,
list_[i].token_pos, list_[i].is_generated);
handlers.SetHandledTypes(i, Array::empty_array());
} else {
const bool has_catch_all = ContainsDynamic(*list_[i].handler_types);
handlers.SetHandlerInfo(i, list_[i].outer_try_index, list_[i].pc_offset,
list_[i].needs_stacktrace, has_catch_all,
list_[i].token_pos, list_[i].is_generated);
handlers.SetHandledTypes(i, *list_[i].handler_types);
}
}
return handlers.raw();
}
static uint8_t* zone_allocator(uint8_t* ptr,
intptr_t old_size,
intptr_t new_size) {
Zone* zone = Thread::Current()->zone();
return zone->Realloc<uint8_t>(ptr, old_size, new_size);
}
class CatchEntryStateMapBuilder::TrieNode : public ZoneAllocated {
public:
TrieNode() : pair_(), entry_state_offset_(-1) {}
TrieNode(CatchEntryStatePair pair, intptr_t index)
: pair_(pair), entry_state_offset_(index) {}
intptr_t Offset() { return entry_state_offset_; }
TrieNode* Insert(TrieNode* node) {
children_.Add(node);
return node;
}
TrieNode* Follow(CatchEntryStatePair next) {
for (intptr_t i = 0; i < children_.length(); i++) {
if (children_[i]->pair_ == next) return children_[i];
}
return NULL;
}
private:
CatchEntryStatePair pair_;
const intptr_t entry_state_offset_;
GrowableArray<TrieNode*> children_;
};
CatchEntryStateMapBuilder::CatchEntryStateMapBuilder()
: zone_(Thread::Current()->zone()),
root_(new TrieNode()),
current_pc_offset_(0),
buffer_(NULL),
stream_(&buffer_, zone_allocator, 64) {}
void CatchEntryStateMapBuilder::AppendMove(intptr_t src_slot,
intptr_t dest_slot) {
moves_.Add(CatchEntryStatePair::FromMove(src_slot, dest_slot));
}
void CatchEntryStateMapBuilder::AppendConstant(intptr_t pool_id,
intptr_t dest_slot) {
moves_.Add(CatchEntryStatePair::FromConstant(pool_id, dest_slot));
}
void CatchEntryStateMapBuilder::NewMapping(intptr_t pc_offset) {
moves_.Clear();
current_pc_offset_ = pc_offset;
}
void CatchEntryStateMapBuilder::EndMapping() {
intptr_t suffix_length = 0;
TrieNode* suffix = root_;
// Find the largest common suffix, get the last node of the path.
for (intptr_t i = moves_.length() - 1; i >= 0; i--) {
TrieNode* n = suffix->Follow(moves_[i]);
if (n == NULL) break;
suffix_length++;
suffix = n;
}
intptr_t length = moves_.length() - suffix_length;
intptr_t current_offset = stream_.bytes_written();
typedef WriteStream::Raw<sizeof(intptr_t), intptr_t> Writer;
Writer::Write(&stream_, current_pc_offset_);
Writer::Write(&stream_, length);
Writer::Write(&stream_, suffix_length);
Writer::Write(&stream_, suffix->Offset());
// Write the unshared part, adding it to the trie.
TrieNode* node = suffix;
for (intptr_t i = length - 1; i >= 0; i--) {
Writer::Write(&stream_, moves_[i].src);
Writer::Write(&stream_, moves_[i].dest);
TrieNode* child = new (zone_) TrieNode(moves_[i], current_offset);
node->Insert(child);
node = child;
}
}
RawTypedData* CatchEntryStateMapBuilder::FinalizeCatchEntryStateMap() {
TypedData& td = TypedData::Handle(TypedData::New(
kTypedDataInt8ArrayCid, stream_.bytes_written(), Heap::kOld));
NoSafepointScope no_safepoint;
uint8_t* dest = reinterpret_cast<uint8_t*>(td.DataAddr(0));
uint8_t* src = stream_.buffer();
for (intptr_t i = 0; i < stream_.bytes_written(); i++) {
dest[i] = src[i];
}
return td.raw();
}
const TokenPosition CodeSourceMapBuilder::kInitialPosition =
TokenPosition(TokenPosition::kDartCodeProloguePos);
CodeSourceMapBuilder::CodeSourceMapBuilder(
bool stack_traces_only,
const GrowableArray<intptr_t>& caller_inline_id,
const GrowableArray<TokenPosition>& inline_id_to_token_pos,
const GrowableArray<const Function*>& inline_id_to_function)
: buffered_pc_offset_(0),
buffered_inline_id_stack_(),
buffered_token_pos_stack_(),
written_pc_offset_(0),
written_inline_id_stack_(),
written_token_pos_stack_(),
caller_inline_id_(caller_inline_id),
inline_id_to_token_pos_(inline_id_to_token_pos),
inline_id_to_function_(inline_id_to_function),
inlined_functions_(
GrowableObjectArray::Handle(GrowableObjectArray::New(Heap::kOld))),
buffer_(NULL),
stream_(&buffer_, zone_allocator, 64),
stack_traces_only_(stack_traces_only) {
buffered_inline_id_stack_.Add(0);
buffered_token_pos_stack_.Add(kInitialPosition);
written_inline_id_stack_.Add(0);
written_token_pos_stack_.Add(kInitialPosition);
}
void CodeSourceMapBuilder::FlushBuffer() {
FlushBufferStack();
FlushBufferPosition();
FlushBufferPC();
}
void CodeSourceMapBuilder::FlushBufferStack() {
for (intptr_t i = buffered_inline_id_stack_.length() - 1; i >= 0; i--) {
intptr_t buffered_id = buffered_inline_id_stack_[i];
if (i < written_inline_id_stack_.length()) {
intptr_t written_id = written_inline_id_stack_[i];
if (buffered_id == written_id) {
// i is the top-most position where the buffered and written stack
// match.
while (written_inline_id_stack_.length() > i + 1) {
WritePop();
}
for (intptr_t j = i + 1; j < buffered_inline_id_stack_.length(); j++) {
TokenPosition buffered_pos = buffered_token_pos_stack_[j - 1];
TokenPosition written_pos = written_token_pos_stack_[j - 1];
if (buffered_pos != written_pos) {
WriteChangePosition(buffered_pos);
}
WritePush(buffered_inline_id_stack_[j]);
}
return;
}
}
}
UNREACHABLE();
}
void CodeSourceMapBuilder::FlushBufferPosition() {
ASSERT(buffered_token_pos_stack_.length() ==
written_token_pos_stack_.length());
intptr_t top = buffered_token_pos_stack_.length() - 1;
TokenPosition buffered_pos = buffered_token_pos_stack_[top];
TokenPosition written_pos = written_token_pos_stack_[top];
if (buffered_pos != written_pos) {
WriteChangePosition(buffered_pos);
}
}
void CodeSourceMapBuilder::FlushBufferPC() {
if (buffered_pc_offset_ != written_pc_offset_) {
WriteAdvancePC(buffered_pc_offset_ - written_pc_offset_);
}
}
void CodeSourceMapBuilder::StartInliningInterval(int32_t pc_offset,
intptr_t inline_id) {
if (buffered_inline_id_stack_.Last() == inline_id) {
// No change in function stack.
return;
}
if (inline_id == -1) {
// Basic blocking missing an inline_id.
return;
}
if (!stack_traces_only_) {
FlushBuffer();
}
// Find a minimal set of pops and pushes to bring us to the new function
// stack.
// Pop to a common ancestor.
intptr_t common_parent = inline_id;
while (!IsOnBufferedStack(common_parent)) {
common_parent = caller_inline_id_[common_parent];
}
while (buffered_inline_id_stack_.Last() != common_parent) {
BufferPop();
}
// Push to the new top-of-stack function.
GrowableArray<intptr_t> to_push;
intptr_t id = inline_id;
while (id != common_parent) {
to_push.Add(id);
id = caller_inline_id_[id];
}
for (intptr_t i = to_push.length() - 1; i >= 0; i--) {
intptr_t callee_id = to_push[i];
TokenPosition call_token;
if (callee_id != 0) {
// TODO(rmacnak): Should make this array line up with the others.
call_token = inline_id_to_token_pos_[callee_id - 1];
} else {
UNREACHABLE();
}
// Report caller as at the position of the call.
BufferChangePosition(call_token);
BufferPush(callee_id);
}
}
void CodeSourceMapBuilder::BeginCodeSourceRange(int32_t pc_offset) {}
void CodeSourceMapBuilder::EndCodeSourceRange(int32_t pc_offset,
TokenPosition pos) {
if (pc_offset == buffered_pc_offset_) {
return; // Empty intermediate instruction.
}
if (pos != buffered_token_pos_stack_.Last()) {
if (!stack_traces_only_) {
FlushBuffer();
}
BufferChangePosition(pos);
}
BufferAdvancePC(pc_offset - buffered_pc_offset_);
}
void CodeSourceMapBuilder::NoteDescriptor(RawPcDescriptors::Kind kind,
int32_t pc_offset,
TokenPosition pos) {
const uint8_t kCanThrow =
RawPcDescriptors::kIcCall | RawPcDescriptors::kUnoptStaticCall |
RawPcDescriptors::kRuntimeCall | RawPcDescriptors::kOther;
if (stack_traces_only_ && ((kind & kCanThrow) != 0)) {
BufferChangePosition(pos);
BufferAdvancePC(pc_offset - buffered_pc_offset_);
FlushBuffer();
}
}
intptr_t CodeSourceMapBuilder::GetFunctionId(intptr_t inline_id) {
const Function& function = *inline_id_to_function_[inline_id];
for (intptr_t i = 0; i < inlined_functions_.Length(); i++) {
if (inlined_functions_.At(i) == function.raw()) {
return i;
}
}
inlined_functions_.Add(function, Heap::kOld);
return inlined_functions_.Length() - 1;
}
RawArray* CodeSourceMapBuilder::InliningIdToFunction() {
if (inlined_functions_.Length() == 0) {
return Object::empty_array().raw();
}
return Array::MakeFixedLength(inlined_functions_);
}
RawCodeSourceMap* CodeSourceMapBuilder::Finalize() {
if (!stack_traces_only_) {
FlushBuffer();
}
intptr_t length = stream_.bytes_written();
const CodeSourceMap& map = CodeSourceMap::Handle(CodeSourceMap::New(length));
NoSafepointScope no_safepoint;
memmove(map.Data(), buffer_, length);
return map.raw();
}
void CodeSourceMapBuilder::WriteChangePosition(TokenPosition pos) {
stream_.Write<uint8_t>(kChangePosition);
if (FLAG_precompiled_mode) {
intptr_t line = -1;
intptr_t inline_id = buffered_inline_id_stack_.Last();
if (inline_id < inline_id_to_function_.length()) {
const Function* function = inline_id_to_function_[inline_id];
Script& script = Script::Handle(function->script());
line = script.GetTokenLineUsingLineStarts(pos.SourcePosition());
}
stream_.Write<int32_t>(static_cast<int32_t>(line));
} else {
stream_.Write<int32_t>(static_cast<int32_t>(pos.value()));
}
written_token_pos_stack_.Last() = pos;
}
void CodeSourceMapReader::GetInlinedFunctionsAt(
int32_t pc_offset,
GrowableArray<const Function*>* function_stack,
GrowableArray<TokenPosition>* token_positions) {
function_stack->Clear();
token_positions->Clear();
NoSafepointScope no_safepoint;
ReadStream stream(map_.Data(), map_.Length());
int32_t current_pc_offset = 0;
function_stack->Add(&root_);
token_positions->Add(CodeSourceMapBuilder::kInitialPosition);
while (stream.PendingBytes() > 0) {
uint8_t opcode = stream.Read<uint8_t>();
switch (opcode) {
case CodeSourceMapBuilder::kChangePosition: {
int32_t position = stream.Read<int32_t>();
(*token_positions)[token_positions->length() - 1] =
TokenPosition(position);
break;
}
case CodeSourceMapBuilder::kAdvancePC: {
int32_t delta = stream.Read<int32_t>();
current_pc_offset += delta;
if (current_pc_offset > pc_offset) {
return;
}
break;
}
case CodeSourceMapBuilder::kPushFunction: {
int32_t func = stream.Read<int32_t>();
function_stack->Add(
&Function::Handle(Function::RawCast(functions_.At(func))));
token_positions->Add(CodeSourceMapBuilder::kInitialPosition);
break;
}
case CodeSourceMapBuilder::kPopFunction: {
// We never pop the root function.
ASSERT(function_stack->length() > 1);
ASSERT(token_positions->length() > 1);
function_stack->RemoveLast();
token_positions->RemoveLast();
break;
}
default:
UNREACHABLE();
}
}
}
#ifndef PRODUCT
void CodeSourceMapReader::PrintJSONInlineIntervals(JSONObject* jsobj) {
{
JSONArray inlined_functions(jsobj, "_inlinedFunctions");
Function& function = Function::Handle();
for (intptr_t i = 0; i < functions_.Length(); i++) {
function ^= functions_.At(i);
ASSERT(!function.IsNull());
inlined_functions.AddValue(function);
}
}
GrowableArray<intptr_t> function_stack;
JSONArray inline_intervals(jsobj, "_inlinedIntervals");
NoSafepointScope no_safepoint;
ReadStream stream(map_.Data(), map_.Length());
int32_t current_pc_offset = 0;
function_stack.Add(0);
while (stream.PendingBytes() > 0) {
uint8_t opcode = stream.Read<uint8_t>();
switch (opcode) {
case CodeSourceMapBuilder::kChangePosition: {
stream.Read<int32_t>();
break;
}
case CodeSourceMapBuilder::kAdvancePC: {
int32_t delta = stream.Read<int32_t>();
// Format: [start, end, inline functions...]
JSONArray inline_interval(&inline_intervals);
inline_interval.AddValue(static_cast<intptr_t>(current_pc_offset));
inline_interval.AddValue(
static_cast<intptr_t>(current_pc_offset + delta - 1));
for (intptr_t i = 0; i < function_stack.length(); i++) {
inline_interval.AddValue(function_stack[i]);
}
current_pc_offset += delta;
break;
}
case CodeSourceMapBuilder::kPushFunction: {
int32_t func = stream.Read<int32_t>();
function_stack.Add(func);
break;
}
case CodeSourceMapBuilder::kPopFunction: {
// We never pop the root function.
ASSERT(function_stack.length() > 1);
function_stack.RemoveLast();
break;
}
default:
UNREACHABLE();
}
}
}
#endif // !PRODUCT
void CodeSourceMapReader::DumpInlineIntervals(uword start) {
GrowableArray<const Function*> function_stack;
LogBlock lb;
NoSafepointScope no_safepoint;
ReadStream stream(map_.Data(), map_.Length());
int32_t current_pc_offset = 0;
function_stack.Add(&root_);
THR_Print("Inline intervals {\n");
while (stream.PendingBytes() > 0) {
uint8_t opcode = stream.Read<uint8_t>();
switch (opcode) {
case CodeSourceMapBuilder::kChangePosition: {
stream.Read<int32_t>();
break;
}
case CodeSourceMapBuilder::kAdvancePC: {
int32_t delta = stream.Read<int32_t>();
THR_Print("%" Px "-%" Px ": ", start + current_pc_offset,
start + current_pc_offset + delta - 1);
for (intptr_t i = 0; i < function_stack.length(); i++) {
THR_Print("%s ", function_stack[i]->ToCString());
}
THR_Print("\n");
current_pc_offset += delta;
break;
}
case CodeSourceMapBuilder::kPushFunction: {
int32_t func = stream.Read<int32_t>();
function_stack.Add(
&Function::Handle(Function::RawCast(functions_.At(func))));
break;
}
case CodeSourceMapBuilder::kPopFunction: {
// We never pop the root function.
ASSERT(function_stack.length() > 1);
function_stack.RemoveLast();
break;
}
default:
UNREACHABLE();
}
}
THR_Print("}\n");
}
void CodeSourceMapReader::DumpSourcePositions(uword start) {
GrowableArray<const Function*> function_stack;
GrowableArray<TokenPosition> token_positions;
LogBlock lb;
NoSafepointScope no_safepoint;
ReadStream stream(map_.Data(), map_.Length());
int32_t current_pc_offset = 0;
function_stack.Add(&root_);
token_positions.Add(CodeSourceMapBuilder::kInitialPosition);
THR_Print("Source positions {\n");
while (stream.PendingBytes() > 0) {
uint8_t opcode = stream.Read<uint8_t>();
switch (opcode) {
case CodeSourceMapBuilder::kChangePosition: {
int32_t position = stream.Read<int32_t>();
token_positions[token_positions.length() - 1] = TokenPosition(position);
break;
}
case CodeSourceMapBuilder::kAdvancePC: {
int32_t delta = stream.Read<int32_t>();
THR_Print("%" Px "-%" Px ": ", start + current_pc_offset,
start + current_pc_offset + delta - 1);
for (intptr_t i = 0; i < function_stack.length(); i++) {
THR_Print("%s@%" Pd " ", function_stack[i]->ToCString(),
token_positions[i].value());
}
THR_Print("\n");
current_pc_offset += delta;
break;
}
case CodeSourceMapBuilder::kPushFunction: {
int32_t func = stream.Read<int32_t>();
function_stack.Add(
&Function::Handle(Function::RawCast(functions_.At(func))));
token_positions.Add(CodeSourceMapBuilder::kInitialPosition);
break;
}
case CodeSourceMapBuilder::kPopFunction: {
// We never pop the root function.
ASSERT(function_stack.length() > 1);
ASSERT(token_positions.length() > 1);
function_stack.RemoveLast();
token_positions.RemoveLast();
break;
}
default:
UNREACHABLE();
}
}
THR_Print("}\n");
}
} // namespace dart