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// Copyright 2017 The Dawn Authors
//
// 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 "dawn_native/CommandAllocator.h"
#include "common/Assert.h"
#include "common/Math.h"
#include <algorithm>
#include <climits>
#include <cstdlib>
namespace dawn_native {
constexpr uint32_t EndOfBlock = UINT_MAX; // std::numeric_limits<uint32_t>::max();
constexpr uint32_t AdditionalData = UINT_MAX - 1; // std::numeric_limits<uint32_t>::max() - 1;
// TODO(cwallez@chromium.org): figure out a way to have more type safety for the iterator
CommandIterator::CommandIterator() : mEndOfBlock(EndOfBlock) {
Reset();
}
CommandIterator::~CommandIterator() {
ASSERT(mDataWasDestroyed);
if (!IsEmpty()) {
for (auto& block : mBlocks) {
free(block.block);
}
}
}
CommandIterator::CommandIterator(CommandIterator&& other) : mEndOfBlock(EndOfBlock) {
if (!other.IsEmpty()) {
mBlocks = std::move(other.mBlocks);
other.Reset();
}
other.DataWasDestroyed();
Reset();
}
CommandIterator& CommandIterator::operator=(CommandIterator&& other) {
if (!other.IsEmpty()) {
mBlocks = std::move(other.mBlocks);
other.Reset();
} else {
mBlocks.clear();
}
other.DataWasDestroyed();
Reset();
return *this;
}
CommandIterator::CommandIterator(CommandAllocator&& allocator)
: mBlocks(allocator.AcquireBlocks()), mEndOfBlock(EndOfBlock) {
Reset();
}
CommandIterator& CommandIterator::operator=(CommandAllocator&& allocator) {
mBlocks = allocator.AcquireBlocks();
Reset();
return *this;
}
void CommandIterator::Reset() {
mCurrentBlock = 0;
if (mBlocks.empty()) {
// This will case the first NextCommandId call to try to move to the next block and stop
// the iteration immediately, without special casing the initialization.
mCurrentPtr = reinterpret_cast<uint8_t*>(&mEndOfBlock);
mBlocks.emplace_back();
mBlocks[0].size = sizeof(mEndOfBlock);
mBlocks[0].block = mCurrentPtr;
} else {
mCurrentPtr = AlignPtr(mBlocks[0].block, alignof(uint32_t));
}
}
void CommandIterator::DataWasDestroyed() {
mDataWasDestroyed = true;
}
bool CommandIterator::IsEmpty() const {
return mBlocks[0].block == reinterpret_cast<const uint8_t*>(&mEndOfBlock);
}
bool CommandIterator::NextCommandId(uint32_t* commandId) {
uint8_t* idPtr = AlignPtr(mCurrentPtr, alignof(uint32_t));
ASSERT(idPtr + sizeof(uint32_t) <=
mBlocks[mCurrentBlock].block + mBlocks[mCurrentBlock].size);
uint32_t id = *reinterpret_cast<uint32_t*>(idPtr);
if (id == EndOfBlock) {
mCurrentBlock++;
if (mCurrentBlock >= mBlocks.size()) {
Reset();
*commandId = EndOfBlock;
return false;
}
mCurrentPtr = AlignPtr(mBlocks[mCurrentBlock].block, alignof(uint32_t));
return NextCommandId(commandId);
}
mCurrentPtr = idPtr + sizeof(uint32_t);
*commandId = id;
return true;
}
void* CommandIterator::NextCommand(size_t commandSize, size_t commandAlignment) {
uint8_t* commandPtr = AlignPtr(mCurrentPtr, commandAlignment);
ASSERT(commandPtr + sizeof(commandSize) <=
mBlocks[mCurrentBlock].block + mBlocks[mCurrentBlock].size);
mCurrentPtr = commandPtr + commandSize;
return commandPtr;
}
void* CommandIterator::NextData(size_t dataSize, size_t dataAlignment) {
uint32_t id;
bool hasId = NextCommandId(&id);
ASSERT(hasId);
ASSERT(id == AdditionalData);
return NextCommand(dataSize, dataAlignment);
}
// Potential TODO(cwallez@chromium.org):
// - Host the size and pointer to next block in the block itself to avoid having an allocation
// in the vector
// - Assume T's alignof is, say 64bits, static assert it, and make commandAlignment a constant
// in Allocate
// - Be able to optimize allocation to one block, for command buffers expected to live long to
// avoid cache misses
// - Better block allocation, maybe have Dawn API to say command buffer is going to have size
// close to another
CommandAllocator::CommandAllocator()
: mCurrentPtr(reinterpret_cast<uint8_t*>(&mDummyEnum[0])),
mEndPtr(reinterpret_cast<uint8_t*>(&mDummyEnum[1])) {
}
CommandAllocator::~CommandAllocator() {
ASSERT(mBlocks.empty());
}
CommandBlocks&& CommandAllocator::AcquireBlocks() {
ASSERT(mCurrentPtr != nullptr && mEndPtr != nullptr);
ASSERT(IsPtrAligned(mCurrentPtr, alignof(uint32_t)));
ASSERT(mCurrentPtr + sizeof(uint32_t) <= mEndPtr);
*reinterpret_cast<uint32_t*>(mCurrentPtr) = EndOfBlock;
mCurrentPtr = nullptr;
mEndPtr = nullptr;
return std::move(mBlocks);
}
uint8_t* CommandAllocator::Allocate(uint32_t commandId,
size_t commandSize,
size_t commandAlignment) {
ASSERT(mCurrentPtr != nullptr);
ASSERT(mEndPtr != nullptr);
ASSERT(commandId != EndOfBlock);
// It should always be possible to allocate one id, for EndOfBlock tagging,
ASSERT(IsPtrAligned(mCurrentPtr, alignof(uint32_t)));
ASSERT(mEndPtr >= mCurrentPtr);
ASSERT(static_cast<size_t>(mEndPtr - mCurrentPtr) >= sizeof(uint32_t));
// The memory after the ID will contain the following:
// - the current ID
// - padding to align the command, maximum kMaxSupportedAlignment
// - the command of size commandSize
// - padding to align the next ID, maximum alignof(uint32_t)
// - the next ID of size sizeof(uint32_t)
//
// To avoid checking for overflows at every step of the computations we compute an upper
// bound of the space that will be needed in addition to the command data.
static constexpr size_t kWorstCaseAdditionalSize =
sizeof(uint32_t) + kMaxSupportedAlignment + alignof(uint32_t) + sizeof(uint32_t);
// This can't overflow because by construction mCurrentPtr always has space for the next ID.
size_t remainingSize = static_cast<size_t>(mEndPtr - mCurrentPtr);
// The good case were we have enough space for the command data and upper bound of the
// extra required space.
if ((remainingSize >= kWorstCaseAdditionalSize) &&
(remainingSize - kWorstCaseAdditionalSize >= commandSize)) {
uint32_t* idAlloc = reinterpret_cast<uint32_t*>(mCurrentPtr);
*idAlloc = commandId;
uint8_t* commandAlloc = AlignPtr(mCurrentPtr + sizeof(uint32_t), commandAlignment);
mCurrentPtr = AlignPtr(commandAlloc + commandSize, alignof(uint32_t));
return commandAlloc;
}
// When there is not enough space, we signal the EndOfBlock, so that the iterator knows to
// move to the next one. EndOfBlock on the last block means the end of the commands.
uint32_t* idAlloc = reinterpret_cast<uint32_t*>(mCurrentPtr);
*idAlloc = EndOfBlock;
// We'll request a block that can contain at least the command ID, the command and an
// additional ID to contain the EndOfBlock tag.
size_t requestedBlockSize = commandSize + kWorstCaseAdditionalSize;
// The computation of the request could overflow.
if (DAWN_UNLIKELY(requestedBlockSize <= commandSize)) {
return nullptr;
}
if (DAWN_UNLIKELY(!GetNewBlock(requestedBlockSize))) {
return nullptr;
}
return Allocate(commandId, commandSize, commandAlignment);
}
uint8_t* CommandAllocator::AllocateData(size_t commandSize, size_t commandAlignment) {
return Allocate(AdditionalData, commandSize, commandAlignment);
}
bool CommandAllocator::GetNewBlock(size_t minimumSize) {
// Allocate blocks doubling sizes each time, to a maximum of 16k (or at least minimumSize).
mLastAllocationSize =
std::max(minimumSize, std::min(mLastAllocationSize * 2, size_t(16384)));
uint8_t* block = reinterpret_cast<uint8_t*>(malloc(mLastAllocationSize));
if (DAWN_UNLIKELY(block == nullptr)) {
return false;
}
mBlocks.push_back({mLastAllocationSize, block});
mCurrentPtr = AlignPtr(block, alignof(uint32_t));
mEndPtr = block + mLastAllocationSize;
return true;
}
} // namespace dawn_native