[Interpreter] Replace BytecodeRegisterAllocator with a simple bump pointer.

src/interpreter/bytecode-register-allocator.cc

-// 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),
-      observer_(nullptr) {}
-
-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);
-}
-
-void TemporaryRegisterAllocator::set_observer(
-    TemporaryRegisterObserver* observer) {
-  DCHECK(observer_ == nullptr);
-  observer_ = observer;
-}
-
-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;
-    }
-    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);
-
-  // 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;
-  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);
-  if (observer_) {
-    observer_->TemporaryRegisterFreeEvent(Register(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