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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/interpreter/bytecode-register-allocator.h"
#include "src/interpreter/bytecode-array-builder.h"
namespace v8 {
namespace internal {
namespace interpreter {
TemporaryRegisterAllocator::TemporaryRegisterAllocator(Zone* zone,
int allocation_base)
: free_temporaries_(zone),
allocation_base_(allocation_base),
allocation_count_(0) {}
Register TemporaryRegisterAllocator::first_temporary_register() const {
DCHECK(allocation_count() > 0);
return Register(allocation_base());
}
Register TemporaryRegisterAllocator::last_temporary_register() const {
DCHECK(allocation_count() > 0);
return Register(allocation_base() + allocation_count() - 1);
}
int TemporaryRegisterAllocator::AllocateTemporaryRegister() {
allocation_count_ += 1;
return allocation_base() + allocation_count() - 1;
}
int TemporaryRegisterAllocator::BorrowTemporaryRegister() {
if (free_temporaries_.empty()) {
return AllocateTemporaryRegister();
} else {
auto pos = free_temporaries_.begin();
int retval = *pos;
free_temporaries_.erase(pos);
return retval;
}
}
int TemporaryRegisterAllocator::BorrowTemporaryRegisterNotInRange(
int start_index, int end_index) {
if (free_temporaries_.empty()) {
int next_allocation = allocation_base() + allocation_count();
while (next_allocation >= start_index && next_allocation <= end_index) {
free_temporaries_.insert(AllocateTemporaryRegister());
next_allocation += 1;
}
return AllocateTemporaryRegister();
}
ZoneSet<int>::iterator index = free_temporaries_.lower_bound(start_index);
if (index == free_temporaries_.begin()) {
// If start_index is the first free register, check for a register
// greater than end_index.
index = free_temporaries_.upper_bound(end_index);
if (index == free_temporaries_.end()) {
return AllocateTemporaryRegister();
}
} else {
// If there is a free register < start_index
index--;
}
int retval = *index;
free_temporaries_.erase(index);
return retval;
}
int TemporaryRegisterAllocator::PrepareForConsecutiveTemporaryRegisters(
size_t count) {
if (count == 0) {
return -1;
}
// TODO(oth): replace use of set<> here for free_temporaries with a
// more efficient structure. And/or partition into two searches -
// one before the translation window and one after.
// A run will require at least |count| free temporaries.
while (free_temporaries_.size() < count) {
free_temporaries_.insert(AllocateTemporaryRegister());
}
// Search within existing temporaries for a run.
auto start = free_temporaries_.begin();
size_t run_length = 0;
for (auto run_end = start; run_end != free_temporaries_.end(); run_end++) {
int expected = *start + static_cast<int>(run_length);
if (*run_end != expected) {
start = run_end;
run_length = 0;
}
Register reg_start(*start);
Register reg_expected(expected);
if (RegisterTranslator::DistanceToTranslationWindow(reg_start) > 0 &&
RegisterTranslator::DistanceToTranslationWindow(reg_expected) <= 0) {
// Run straddles the lower edge of the translation window. Registers
// after the start of this boundary are displaced by the register
// translator to provide a hole for translation. Runs either side
// of the boundary are fine.
start = run_end;
run_length = 0;
}
if (++run_length == count) {
return *start;
}
}
// Continue run if possible across existing last temporary.
if (allocation_count_ > 0 && (start == free_temporaries_.end() ||
*start + static_cast<int>(run_length) !=
last_temporary_register().index() + 1)) {
run_length = 0;
}
// Pad temporaries if extended run would cross translation boundary.
Register reg_first(*start);
Register reg_last(*start + static_cast<int>(count) - 1);
DCHECK_GT(RegisterTranslator::DistanceToTranslationWindow(reg_first),
RegisterTranslator::DistanceToTranslationWindow(reg_last));
while (RegisterTranslator::DistanceToTranslationWindow(reg_first) > 0 &&
RegisterTranslator::DistanceToTranslationWindow(reg_last) <= 0) {
auto pos_insert_pair =
free_temporaries_.insert(AllocateTemporaryRegister());
reg_first = Register(*pos_insert_pair.first);
reg_last = Register(reg_first.index() + static_cast<int>(count) - 1);
run_length = 0;
}
// Ensure enough registers for run.
while (run_length++ < count) {
free_temporaries_.insert(AllocateTemporaryRegister());
}
int run_start =
last_temporary_register().index() - static_cast<int>(count) + 1;
DCHECK(RegisterTranslator::DistanceToTranslationWindow(Register(run_start)) <=
0 ||
RegisterTranslator::DistanceToTranslationWindow(
Register(run_start + static_cast<int>(count) - 1)) > 0);
return run_start;
}
bool TemporaryRegisterAllocator::RegisterIsLive(Register reg) const {
if (allocation_count_ > 0) {
DCHECK(reg >= first_temporary_register() &&
reg <= last_temporary_register());
return free_temporaries_.find(reg.index()) == free_temporaries_.end();
} else {
return false;
}
}
void TemporaryRegisterAllocator::BorrowConsecutiveTemporaryRegister(
int reg_index) {
DCHECK(free_temporaries_.find(reg_index) != free_temporaries_.end());
free_temporaries_.erase(reg_index);
}
void TemporaryRegisterAllocator::ReturnTemporaryRegister(int reg_index) {
DCHECK(free_temporaries_.find(reg_index) == free_temporaries_.end());
free_temporaries_.insert(reg_index);
}
BytecodeRegisterAllocator::BytecodeRegisterAllocator(
Zone* zone, TemporaryRegisterAllocator* allocator)
: base_allocator_(allocator),
allocated_(zone),
next_consecutive_register_(-1),
next_consecutive_count_(-1) {}
BytecodeRegisterAllocator::~BytecodeRegisterAllocator() {
for (auto i = allocated_.rbegin(); i != allocated_.rend(); i++) {
base_allocator()->ReturnTemporaryRegister(*i);
}
allocated_.clear();
}
Register BytecodeRegisterAllocator::NewRegister() {
int allocated = -1;
if (next_consecutive_count_ <= 0) {
allocated = base_allocator()->BorrowTemporaryRegister();
} else {
allocated = base_allocator()->BorrowTemporaryRegisterNotInRange(
next_consecutive_register_,
next_consecutive_register_ + next_consecutive_count_ - 1);
}
allocated_.push_back(allocated);
return Register(allocated);
}
bool BytecodeRegisterAllocator::RegisterIsAllocatedInThisScope(
Register reg) const {
for (auto i = allocated_.begin(); i != allocated_.end(); i++) {
if (*i == reg.index()) return true;
}
return false;
}
void BytecodeRegisterAllocator::PrepareForConsecutiveAllocations(size_t count) {
if (static_cast<int>(count) > next_consecutive_count_) {
next_consecutive_register_ =
base_allocator()->PrepareForConsecutiveTemporaryRegisters(count);
next_consecutive_count_ = static_cast<int>(count);
}
}
Register BytecodeRegisterAllocator::NextConsecutiveRegister() {
DCHECK_GE(next_consecutive_register_, 0);
DCHECK_GT(next_consecutive_count_, 0);
base_allocator()->BorrowConsecutiveTemporaryRegister(
next_consecutive_register_);
allocated_.push_back(next_consecutive_register_);
next_consecutive_count_--;
return Register(next_consecutive_register_++);
}
} // namespace interpreter
} // namespace internal
} // namespace v8
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