runtime/lambda/closure_builder.cc - platform/art - Git at Google

 /*
  * 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
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * 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));

   values_.push_back(storage);
   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.
   values_.push_back(reinterpret_cast<ShortyFieldTypeTraits::MaxType>(closure));

   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 =
         WriteValues(target_method,
                     closure->captured_[0].dynamic_.variables_,
                     header_size,
                     variables_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 =
         WriteValues(target_method,
                     closure->captured_[0].static_variables_,
                     header_size,
                     variables_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 {
       DCHECK(shorty.IsLambda())
           << " 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
	/*
	* 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
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* 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));

	values_.push_back(storage);
	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.
	values_.push_back(reinterpret_cast<ShortyFieldTypeTraits::MaxType>(closure));

	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 =
	WriteValues(target_method,
	closure->captured_[0].dynamic_.variables_,
	header_size,
	variables_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 =
	WriteValues(target_method,
	closure->captured_[0].static_variables_,
	header_size,
	variables_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 {
	DCHECK(shorty.IsLambda())
	<< " 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