class RubyVM::RJIT::Context

# File ruby_vm/rjit/context.rb, line 26
  def initialize(
    stack_size:   0,
    sp_offset:    0,
    chain_depth:  0,
    local_types:  [Type::Unknown] * MAX_LOCAL_TYPES,
    temp_types:   [Type::Unknown] * MAX_TEMP_TYPES,
    self_type:    Type::Unknown,
    temp_mapping: [MapToStack] * MAX_TEMP_TYPES
  ) = super

  # Deep dup by default for safety
  def dup
    ctx = super
    ctx.local_types = ctx.local_types.dup
    ctx.temp_types = ctx.temp_types.dup
    ctx.temp_mapping = ctx.temp_mapping.dup
    ctx
  end

  # Create a new Context instance with a given stack_size and sp_offset adjusted
  # accordingly. This is useful when you want to virtually rewind a stack_size for
  # generating a side exit while considering past sp_offset changes on gen_save_sp.
  def with_stack_size(stack_size)
    ctx = self.dup
    ctx.sp_offset -= ctx.stack_size - stack_size
    ctx.stack_size = stack_size
    ctx
  end

  def stack_opnd(depth_from_top)
    [SP, C.VALUE.size * (self.sp_offset - 1 - depth_from_top)]
  end

  def sp_opnd(offset_bytes = 0)
    [SP, (C.VALUE.size * self.sp_offset) + offset_bytes]
  end

  # Push one new value on the temp stack with an explicit mapping
  # Return a pointer to the new stack top
  def stack_push_mapping(mapping_temp_type)
    stack_size = self.stack_size

    # Keep track of the type and mapping of the value
    if stack_size < MAX_TEMP_TYPES
      mapping, temp_type = mapping_temp_type
      self.temp_mapping[stack_size] = mapping
      self.temp_types[stack_size] = temp_type

      case mapping
      in MapToLocal[idx]
        assert(idx < MAX_LOCAL_TYPES)
      else
      end
    end

    self.stack_size += 1
    self.sp_offset += 1

    return self.stack_opnd(0)
  end

  # Push one new value on the temp stack
  # Return a pointer to the new stack top
  def stack_push(val_type)
    return self.stack_push_mapping([MapToStack, val_type])
  end

  # Push the self value on the stack
  def stack_push_self
    return self.stack_push_mapping([MapToStack, Type::Unknown])
  end

  # Push a local variable on the stack
  def stack_push_local(local_idx)
    if local_idx >= MAX_LOCAL_TYPES
      return self.stack_push(Type::Unknown)
    end

    return self.stack_push_mapping([MapToLocal[local_idx], Type::Unknown])
  end

  # Pop N values off the stack
  # Return a pointer to the stack top before the pop operation
  def stack_pop(n = 1)
    assert(n <= self.stack_size)

    top = self.stack_opnd(0)

    # Clear the types of the popped values
    n.times do |i|
      idx = self.stack_size - i - 1

      if idx < MAX_TEMP_TYPES
        self.temp_types[idx] = Type::Unknown
        self.temp_mapping[idx] = MapToStack
      end
    end

    self.stack_size -= n
    self.sp_offset -= n

    return top
  end

  def shift_stack(argc)
    assert(argc < self.stack_size)

    method_name_index = self.stack_size - argc - 1

    (method_name_index...(self.stack_size - 1)).each do |i|
      if i + 1 < MAX_TEMP_TYPES
        self.temp_types[i] = self.temp_types[i + 1]
        self.temp_mapping[i] = self.temp_mapping[i + 1]
      end
    end
    self.stack_pop(1)
  end

  # Get the type of an instruction operand
  def get_opnd_type(opnd)
    case opnd
    in SelfOpnd
      self.self_type
    in StackOpnd[idx]
      assert(idx < self.stack_size)
      stack_idx = self.stack_size - 1 - idx

      # If outside of tracked range, do nothing
      if stack_idx >= MAX_TEMP_TYPES
        return Type::Unknown
      end

      mapping = self.temp_mapping[stack_idx]

      case mapping
      in MapToSelf
        self.self_type
      in MapToStack
        self.temp_types[self.stack_size - 1 - idx]
      in MapToLocal[idx]
        assert(idx < MAX_LOCAL_TYPES)
        self.local_types[idx]
      end
    end
  end

  # Get the currently tracked type for a local variable
  def get_local_type(idx)
    self.local_types[idx] || Type::Unknown
  end

  # Upgrade (or "learn") the type of an instruction operand
  # This value must be compatible and at least as specific as the previously known type.
  # If this value originated from self, or an lvar, the learned type will be
  # propagated back to its source.
  def upgrade_opnd_type(opnd, opnd_type)
    case opnd
    in SelfOpnd
      self.self_type = self.self_type.upgrade(opnd_type)
    in StackOpnd[idx]
      assert(idx < self.stack_size)
      stack_idx = self.stack_size - 1 - idx

      # If outside of tracked range, do nothing
      if stack_idx >= MAX_TEMP_TYPES
        return
      end

      mapping = self.temp_mapping[stack_idx]

      case mapping
      in MapToSelf
        self.self_type = self.self_type.upgrade(opnd_type)
      in MapToStack
        self.temp_types[stack_idx] = self.temp_types[stack_idx].upgrade(opnd_type)
      in MapToLocal[idx]
        assert(idx < MAX_LOCAL_TYPES)
        self.local_types[idx] = self.local_types[idx].upgrade(opnd_type)
      end
    end
  end

  # Get both the type and mapping (where the value originates) of an operand.
  # This is can be used with stack_push_mapping or set_opnd_mapping to copy
  # a stack value's type while maintaining the mapping.
  def get_opnd_mapping(opnd)
    opnd_type = self.get_opnd_type(opnd)

    case opnd
    in SelfOpnd
      return [MapToSelf, opnd_type]
    in StackOpnd[idx]
      assert(idx < self.stack_size)
      stack_idx = self.stack_size - 1 - idx

      if stack_idx < MAX_TEMP_TYPES
        return [self.temp_mapping[stack_idx], opnd_type]
      else
        # We can't know the source of this stack operand, so we assume it is
        # a stack-only temporary. type will be UNKNOWN
        assert(opnd_type == Type::Unknown)
        return [MapToStack, opnd_type]
      end
    end
  end

  # Overwrite both the type and mapping of a stack operand.
  def set_opnd_mapping(opnd, mapping_opnd_type)
    case opnd
    in SelfOpnd
      raise 'self always maps to self'
    in StackOpnd[idx]
      assert(idx < self.stack_size)
      stack_idx = self.stack_size - 1 - idx

      # If outside of tracked range, do nothing
      if stack_idx >= MAX_TEMP_TYPES
        return
      end

      mapping, opnd_type = mapping_opnd_type
      self.temp_mapping[stack_idx] = mapping

      # Only used when mapping == MAP_STACK
      self.temp_types[stack_idx] = opnd_type
    end
  end

  # Set the type of a local variable
  def set_local_type(local_idx, local_type)
    if local_idx >= MAX_LOCAL_TYPES
      return
    end

    # If any values on the stack map to this local we must detach them
    MAX_TEMP_TYPES.times do |stack_idx|
      case self.temp_mapping[stack_idx]
      in MapToStack
        # noop
      in MapToSelf
        # noop
      in MapToLocal[idx]
        if idx == local_idx
          self.temp_types[stack_idx] = self.local_types[idx]
          self.temp_mapping[stack_idx] = MapToStack
        else
          # noop
        end
      end
    end

    self.local_types[local_idx] = local_type
  end

  # Erase local variable type information
  # eg: because of a call we can't track
  def clear_local_types
    # When clearing local types we must detach any stack mappings to those
    # locals. Even if local values may have changed, stack values will not.
    MAX_TEMP_TYPES.times do |stack_idx|
      case self.temp_mapping[stack_idx]
      in MapToStack
        # noop
      in MapToSelf
        # noop
      in MapToLocal[local_idx]
        self.temp_types[stack_idx] = self.local_types[local_idx]
        self.temp_mapping[stack_idx] = MapToStack
      end
    end

    # Clear the local types
    self.local_types = [Type::Unknown] * MAX_LOCAL_TYPES
  end

  # Compute a difference score for two context objects
  def diff(dst)
    # Self is the source context (at the end of the predecessor)
    src = self

    # Can only lookup the first version in the chain
    if dst.chain_depth != 0
      return TypeDiff::Incompatible
    end

    # Blocks with depth > 0 always produce new versions
    # Sidechains cannot overlap
    if src.chain_depth != 0
      return TypeDiff::Incompatible
    end

    if dst.stack_size != src.stack_size
      return TypeDiff::Incompatible
    end

    if dst.sp_offset != src.sp_offset
      return TypeDiff::Incompatible
    end

    # Difference sum
    diff = 0

    # Check the type of self
    diff += case src.self_type.diff(dst.self_type)
    in TypeDiff::Compatible[diff] then diff
    in TypeDiff::Incompatible then return TypeDiff::Incompatible
    end

    # For each local type we track
    src.local_types.size.times do |i|
      t_src = src.local_types[i]
      t_dst = dst.local_types[i]
      diff += case t_src.diff(t_dst)
      in TypeDiff::Compatible[diff] then diff
      in TypeDiff::Incompatible then return TypeDiff::Incompatible
      end
    end

    # For each value on the temp stack
    src.stack_size.times do |i|
      src_mapping, src_type = src.get_opnd_mapping(StackOpnd[i])
      dst_mapping, dst_type = dst.get_opnd_mapping(StackOpnd[i])

      # If the two mappings aren't the same
      if src_mapping != dst_mapping
        if dst_mapping == MapToStack
          # We can safely drop information about the source of the temp
          # stack operand.
          diff += 1
        else
          return TypeDiff::Incompatible
        end
      end

      diff += case src_type.diff(dst_type)
      in TypeDiff::Compatible[diff] then diff
      in TypeDiff::Incompatible then return TypeDiff::Incompatible
      end
    end

    return TypeDiff::Compatible[diff]
  end

  private

  def assert(cond)
    unless cond
      raise "'#{cond.inspect}' was not true"
    end
  end
end

# File ruby_vm/rjit/context.rb, line 371
def assert(cond)
  unless cond
    raise "'#{cond.inspect}' was not true"
  end
end

# File ruby_vm/rjit/context.rb, line 282
def clear_local_types
  # When clearing local types we must detach any stack mappings to those
  # locals. Even if local values may have changed, stack values will not.
  MAX_TEMP_TYPES.times do |stack_idx|
    case self.temp_mapping[stack_idx]
    in MapToStack
      # noop
    in MapToSelf
      # noop
    in MapToLocal[local_idx]
      self.temp_types[stack_idx] = self.local_types[local_idx]
      self.temp_mapping[stack_idx] = MapToStack
    end
  end

  # Clear the local types
  self.local_types = [Type::Unknown] * MAX_LOCAL_TYPES
end

# File ruby_vm/rjit/context.rb, line 302
def diff(dst)
  # Self is the source context (at the end of the predecessor)
  src = self

  # Can only lookup the first version in the chain
  if dst.chain_depth != 0
    return TypeDiff::Incompatible
  end

  # Blocks with depth > 0 always produce new versions
  # Sidechains cannot overlap
  if src.chain_depth != 0
    return TypeDiff::Incompatible
  end

  if dst.stack_size != src.stack_size
    return TypeDiff::Incompatible
  end

  if dst.sp_offset != src.sp_offset
    return TypeDiff::Incompatible
  end

  # Difference sum
  diff = 0

  # Check the type of self
  diff += case src.self_type.diff(dst.self_type)
  in TypeDiff::Compatible[diff] then diff
  in TypeDiff::Incompatible then return TypeDiff::Incompatible
  end

  # For each local type we track
  src.local_types.size.times do |i|
    t_src = src.local_types[i]
    t_dst = dst.local_types[i]
    diff += case t_src.diff(t_dst)
    in TypeDiff::Compatible[diff] then diff
    in TypeDiff::Incompatible then return TypeDiff::Incompatible
    end
  end

  # For each value on the temp stack
  src.stack_size.times do |i|
    src_mapping, src_type = src.get_opnd_mapping(StackOpnd[i])
    dst_mapping, dst_type = dst.get_opnd_mapping(StackOpnd[i])

    # If the two mappings aren't the same
    if src_mapping != dst_mapping
      if dst_mapping == MapToStack
        # We can safely drop information about the source of the temp
        # stack operand.
        diff += 1
      else
        return TypeDiff::Incompatible
      end
    end

    diff += case src_type.diff(dst_type)
    in TypeDiff::Compatible[diff] then diff
    in TypeDiff::Incompatible then return TypeDiff::Incompatible
    end
  end

  return TypeDiff::Compatible[diff]
end

# File ruby_vm/rjit/context.rb, line 37
def dup
  ctx = super
  ctx.local_types = ctx.local_types.dup
  ctx.temp_types = ctx.temp_types.dup
  ctx.temp_mapping = ctx.temp_mapping.dup
  ctx
end

# File ruby_vm/rjit/context.rb, line 173
def get_local_type(idx)
  self.local_types[idx] || Type::Unknown
end

# File ruby_vm/rjit/context.rb, line 211
def get_opnd_mapping(opnd)
  opnd_type = self.get_opnd_type(opnd)

  case opnd
  in SelfOpnd
    return [MapToSelf, opnd_type]
  in StackOpnd[idx]
    assert(idx < self.stack_size)
    stack_idx = self.stack_size - 1 - idx

    if stack_idx < MAX_TEMP_TYPES
      return [self.temp_mapping[stack_idx], opnd_type]
    else
      # We can't know the source of this stack operand, so we assume it is
      # a stack-only temporary. type will be UNKNOWN
      assert(opnd_type == Type::Unknown)
      return [MapToStack, opnd_type]
    end
  end
end

# File ruby_vm/rjit/context.rb, line 145
def get_opnd_type(opnd)
  case opnd
  in SelfOpnd
    self.self_type
  in StackOpnd[idx]
    assert(idx < self.stack_size)
    stack_idx = self.stack_size - 1 - idx

    # If outside of tracked range, do nothing
    if stack_idx >= MAX_TEMP_TYPES
      return Type::Unknown
    end

    mapping = self.temp_mapping[stack_idx]

    case mapping
    in MapToSelf
      self.self_type
    in MapToStack
      self.temp_types[self.stack_size - 1 - idx]
    in MapToLocal[idx]
      assert(idx < MAX_LOCAL_TYPES)
      self.local_types[idx]
    end
  end
end

# File ruby_vm/rjit/context.rb, line 255
def set_local_type(local_idx, local_type)
  if local_idx >= MAX_LOCAL_TYPES
    return
  end

  # If any values on the stack map to this local we must detach them
  MAX_TEMP_TYPES.times do |stack_idx|
    case self.temp_mapping[stack_idx]
    in MapToStack
      # noop
    in MapToSelf
      # noop
    in MapToLocal[idx]
      if idx == local_idx
        self.temp_types[stack_idx] = self.local_types[idx]
        self.temp_mapping[stack_idx] = MapToStack
      else
        # noop
      end
    end
  end

  self.local_types[local_idx] = local_type
end

# File ruby_vm/rjit/context.rb, line 233
def set_opnd_mapping(opnd, mapping_opnd_type)
  case opnd
  in SelfOpnd
    raise 'self always maps to self'
  in StackOpnd[idx]
    assert(idx < self.stack_size)
    stack_idx = self.stack_size - 1 - idx

    # If outside of tracked range, do nothing
    if stack_idx >= MAX_TEMP_TYPES
      return
    end

    mapping, opnd_type = mapping_opnd_type
    self.temp_mapping[stack_idx] = mapping

    # Only used when mapping == MAP_STACK
    self.temp_types[stack_idx] = opnd_type
  end
end

# File ruby_vm/rjit/context.rb, line 130
def shift_stack(argc)
  assert(argc < self.stack_size)

  method_name_index = self.stack_size - argc - 1

  (method_name_index...(self.stack_size - 1)).each do |i|
    if i + 1 < MAX_TEMP_TYPES
      self.temp_types[i] = self.temp_types[i + 1]
      self.temp_mapping[i] = self.temp_mapping[i + 1]
    end
  end
  self.stack_pop(1)
end

# File ruby_vm/rjit/context.rb, line 59
def sp_opnd(offset_bytes = 0)
  [SP, (C.VALUE.size * self.sp_offset) + offset_bytes]
end

# File ruby_vm/rjit/context.rb, line 55
def stack_opnd(depth_from_top)
  [SP, C.VALUE.size * (self.sp_offset - 1 - depth_from_top)]
end

# File ruby_vm/rjit/context.rb, line 109
def stack_pop(n = 1)
  assert(n <= self.stack_size)

  top = self.stack_opnd(0)

  # Clear the types of the popped values
  n.times do |i|
    idx = self.stack_size - i - 1

    if idx < MAX_TEMP_TYPES
      self.temp_types[idx] = Type::Unknown
      self.temp_mapping[idx] = MapToStack
    end
  end

  self.stack_size -= n
  self.sp_offset -= n

  return top
end

# File ruby_vm/rjit/context.rb, line 89
def stack_push(val_type)
  return self.stack_push_mapping([MapToStack, val_type])
end

# File ruby_vm/rjit/context.rb, line 99
def stack_push_local(local_idx)
  if local_idx >= MAX_LOCAL_TYPES
    return self.stack_push(Type::Unknown)
  end

  return self.stack_push_mapping([MapToLocal[local_idx], Type::Unknown])
end

# File ruby_vm/rjit/context.rb, line 65
def stack_push_mapping(mapping_temp_type)
  stack_size = self.stack_size

  # Keep track of the type and mapping of the value
  if stack_size < MAX_TEMP_TYPES
    mapping, temp_type = mapping_temp_type
    self.temp_mapping[stack_size] = mapping
    self.temp_types[stack_size] = temp_type

    case mapping
    in MapToLocal[idx]
      assert(idx < MAX_LOCAL_TYPES)
    else
    end
  end

  self.stack_size += 1
  self.sp_offset += 1

  return self.stack_opnd(0)
end

# File ruby_vm/rjit/context.rb, line 94
def stack_push_self
  return self.stack_push_mapping([MapToStack, Type::Unknown])
end

# File ruby_vm/rjit/context.rb, line 181
def upgrade_opnd_type(opnd, opnd_type)
  case opnd
  in SelfOpnd
    self.self_type = self.self_type.upgrade(opnd_type)
  in StackOpnd[idx]
    assert(idx < self.stack_size)
    stack_idx = self.stack_size - 1 - idx

    # If outside of tracked range, do nothing
    if stack_idx >= MAX_TEMP_TYPES
      return
    end

    mapping = self.temp_mapping[stack_idx]

    case mapping
    in MapToSelf
      self.self_type = self.self_type.upgrade(opnd_type)
    in MapToStack
      self.temp_types[stack_idx] = self.temp_types[stack_idx].upgrade(opnd_type)
    in MapToLocal[idx]
      assert(idx < MAX_LOCAL_TYPES)
      self.local_types[idx] = self.local_types[idx].upgrade(opnd_type)
    end
  end
end

# File ruby_vm/rjit/context.rb, line 48
def with_stack_size(stack_size)
  ctx = self.dup
  ctx.sp_offset -= ctx.stack_size - stack_size
  ctx.stack_size = stack_size
  ctx
end