src/register-allocator.cc

// Copyright 2009 the V8 project authors. All rights reserved.
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// modification, are permitted provided that the following conditions are
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//
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#include "v8.h"

#include "codegen-inl.h"
#include "register-allocator-inl.h"
#include "virtual-frame-inl.h"

namespace v8 {
namespace internal {

// -------------------------------------------------------------------------
// Result implementation.


Result::Result(Register reg, TypeInfo info) {
  ASSERT(reg.is_valid() && !RegisterAllocator::IsReserved(reg));
  CodeGeneratorScope::Current()->allocator()->Use(reg);
  value_ = TypeField::encode(REGISTER)
      | TypeInfoField::encode(info.ToInt())
      | DataField::encode(reg.code_);
}


Result::ZoneObjectList* Result::ConstantList() {
  static ZoneObjectList list(10);
  return &list;
}


// -------------------------------------------------------------------------
// RegisterAllocator implementation.


Result RegisterAllocator::AllocateWithoutSpilling() {
  // Return the first free register, if any.
  int num = registers_.ScanForFreeRegister();
  if (num == RegisterAllocator::kInvalidRegister) {
    return Result();
  }
  return Result(RegisterAllocator::ToRegister(num));
}


Result RegisterAllocator::Allocate() {
  Result result = AllocateWithoutSpilling();
  if (!result.is_valid()) {
    // Ask the current frame to spill a register.
    ASSERT(cgen_->has_valid_frame());
    Register free_reg = cgen_->frame()->SpillAnyRegister();
    if (free_reg.is_valid()) {
      ASSERT(!is_used(free_reg));
      return Result(free_reg);
    }
  }
  return result;
}


Result RegisterAllocator::Allocate(Register target) {
  // If the target is not referenced, it can simply be allocated.
  if (!is_used(RegisterAllocator::ToNumber(target))) {
    return Result(target);
  }
  // If the target is only referenced in the frame, it can be spilled and
  // then allocated.
  ASSERT(cgen_->has_valid_frame());
  if (cgen_->frame()->is_used(RegisterAllocator::ToNumber(target)) &&
      count(target) == 1)  {
    cgen_->frame()->Spill(target);
    ASSERT(!is_used(RegisterAllocator::ToNumber(target)));
    return Result(target);
  }
  // Otherwise (if it's referenced outside the frame) we cannot allocate it.
  return Result();
}


} }  // namespace v8::internal