blob: 739e96523858bd8f7c6b8eaafcbe6e2685519e77 [file] [log] [blame]
* Copyright (C) 2015 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include "lambda/closure_builder.h"
#include "base/macros.h"
#include "base/value_object.h"
#include "lambda/art_lambda_method.h"
#include "lambda/closure.h"
#include "lambda/shorty_field_type.h"
#include "runtime/mirror/object_reference.h"
#include <stdint.h>
#include <vector>
namespace art {
namespace lambda {
* GC support TODOs:
* (Although there's some code for storing objects, it is UNIMPLEMENTED(FATAL) because it is
* incomplete).
* 1) GC needs to be able to traverse the Closure and visit any references.
* It might be possible to get away with global roots in the short term.
* 2) Add brooks read barrier support. We can store the black/gray/white bits
* in the lower 2 bits of the lambda art method pointer. Whenever a closure is copied
* [to the stack] we'd need to add a cold path to turn it black.
* (since there's only 3 colors, I can use the 4th value to indicate no-refs).
* e.g. 0x0 = gray, 0x1 = white, 0x2 = black, 0x3 = no-nested-references
* - Alternatively the GC can mark reference-less closures as always-black,
* although it would need extra work to check for references.
void ClosureBuilder::CaptureVariableObject(mirror::Object* object) {
auto compressed_reference = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(object);
ShortyFieldTypeTraits::MaxType storage = 0;
static_assert(sizeof(storage) >= sizeof(compressed_reference),
"not enough room to store a compressed reference");
memcpy(&storage, &compressed_reference, sizeof(compressed_reference));
size_ += kObjectReferenceSize;
static_assert(kObjectReferenceSize == sizeof(compressed_reference), "reference size mismatch");
// TODO: needs more work to support concurrent GC
if (kIsDebugBuild) {
if (kUseReadBarrier) {
UNIMPLEMENTED(FATAL) << "can't yet safely capture objects with read barrier";
shorty_types_ += ShortyFieldType::kObject;
void ClosureBuilder::CaptureVariableLambda(Closure* closure) {
DCHECK(closure != nullptr); // null closures not allowed, target method must be null instead.
if (LIKELY(is_dynamic_size_ == false)) {
// Write in the extra bytes to store the dynamic size the first time.
is_dynamic_size_ = true;
size_ += sizeof(Closure::captured_[0].dynamic_.size_);
// A closure may be sized dynamically, so always query it for the true size.
size_ += closure->GetSize();
shorty_types_ += ShortyFieldType::kLambda;
size_t ClosureBuilder::GetSize() const {
return size_;
size_t ClosureBuilder::GetCaptureCount() const {
DCHECK_EQ(values_.size(), shorty_types_.size());
return values_.size();
const std::string& ClosureBuilder::GetCapturedVariableShortyTypes() const {
DCHECK_EQ(values_.size(), shorty_types_.size());
return shorty_types_;
Closure* ClosureBuilder::CreateInPlace(void* memory, ArtLambdaMethod* target_method) const {
DCHECK(memory != nullptr);
DCHECK(target_method != nullptr);
DCHECK_EQ(is_dynamic_size_, target_method->IsDynamicSize());
CHECK_EQ(target_method->GetNumberOfCapturedVariables(), values_.size())
<< "number of variables captured at runtime does not match "
<< "number of variables captured at compile time";
Closure* closure = new (memory) Closure;
closure->lambda_info_ = target_method;
static_assert(offsetof(Closure, captured_) == kInitialSize, "wrong initial size");
size_t written_size;
if (UNLIKELY(is_dynamic_size_)) {
// The closure size must be set dynamically (i.e. nested lambdas).
closure->captured_[0].dynamic_.size_ = GetSize();
size_t header_size = offsetof(Closure, captured_[0].dynamic_.variables_);
DCHECK_LE(header_size, GetSize());
size_t variables_size = GetSize() - header_size;
written_size =
} else {
// The closure size is known statically (i.e. no nested lambdas).
DCHECK(GetSize() == target_method->GetStaticClosureSize());
size_t header_size = offsetof(Closure, captured_[0].static_variables_);
DCHECK_LE(header_size, GetSize());
size_t variables_size = GetSize() - header_size;
written_size =
DCHECK_EQ(written_size, closure->GetSize());
return closure;
size_t ClosureBuilder::WriteValues(ArtLambdaMethod* target_method,
uint8_t variables[],
size_t header_size,
size_t variables_size) const {
size_t total_size = header_size;
const char* shorty_types = target_method->GetCapturedVariablesShortyTypeDescriptor();
DCHECK_STREQ(shorty_types, shorty_types_.c_str());
size_t variables_offset = 0;
size_t remaining_size = variables_size;
const size_t shorty_count = target_method->GetNumberOfCapturedVariables();
DCHECK_EQ(shorty_count, GetCaptureCount());
for (size_t i = 0; i < shorty_count; ++i) {
ShortyFieldType shorty{shorty_types[i]}; // NOLINT [readability/braces] [4]
size_t var_size;
if (LIKELY(shorty.IsStaticSize())) {
// TODO: needs more work to support concurrent GC, e.g. read barriers
if (kUseReadBarrier == false) {
if (UNLIKELY(shorty.IsObject())) {
UNIMPLEMENTED(FATAL) << "can't yet safely write objects with read barrier";
} else {
if (UNLIKELY(shorty.IsObject())) {
UNIMPLEMENTED(FATAL) << "writing objects not yet supported, no GC support";
var_size = shorty.GetStaticSize();
DCHECK_LE(var_size, sizeof(values_[i]));
// Safe even for objects (non-read barrier case) if we never suspend
// while the ClosureBuilder is live.
// FIXME: Need to add GC support for references in a closure.
memcpy(&variables[variables_offset], &values_[i], var_size);
} else {
<< " don't support writing dynamically sized types other than lambda";
ShortyFieldTypeTraits::MaxType closure_raw = values_[i];
Closure* nested_closure = reinterpret_cast<Closure*>(closure_raw);
DCHECK(nested_closure != nullptr);
nested_closure->CopyTo(&variables[variables_offset], remaining_size);
var_size = nested_closure->GetSize();
total_size += var_size;
DCHECK_GE(remaining_size, var_size);
remaining_size -= var_size;
variables_offset += var_size;
DCHECK_EQ('\0', shorty_types[shorty_count]);
DCHECK_EQ(variables_offset, variables_size);
return total_size;
} // namespace lambda
} // namespace art