Class: Laser::Analysis::ControlFlow::GraphBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/laser/analysis/control_flow/cfg_builder.rb

Overview

This class builds a control flow graph. The algorithm used is derived from Robert Morgan's "Building an Optimizing Compiler".

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (GraphBuilder) initialize(sexp, formals = [], scope = Scope::GlobalScope)

A new instance of GraphBuilder



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 10

def initialize(sexp, formals=[], scope=Scope::GlobalScope)
  @sexp = sexp
  @formals = formals
  @graph = @enter = @exit = nil
  @scope_stack = [scope]
  @self_stack = []
  @temporary_counter = 0
  @temporary_table = Hash.new do |hash, keys|
    @temporary_counter += 1
    hash[keys] = Bindings::TemporaryBinding.new("%t#{@temporary_counter}", nil)
  end
end

Instance Attribute Details

- (Object) current_block (readonly)

Returns the value of attribute current_block



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def current_block
  @current_block
end

- (Object) enter (readonly)

Returns the value of attribute enter



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def enter
  @enter
end

- (Object) exit (readonly)

Returns the value of attribute exit



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def exit
  @exit
end

- (Object) graph (readonly)

Returns the value of attribute graph



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def graph
  @graph
end

- (Object) self_register (readonly)

Returns the value of attribute self_register



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 8

def self_register
  @self_register
end

- (Object) sexp (readonly)

Returns the value of attribute sexp



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def sexp
  @sexp
end

- (Object) temporary_counter (readonly)

Returns the value of attribute temporary_counter



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 7

def temporary_counter
  @temporary_counter
end

Instance Method Details

- (Object) build 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 23

def build
  initialize_graph
  @current_node = @sexp
  @self_register = Bindings::TemporaryBinding.new('self', current_scope.self_ptr)
  build_prologue
  result = walk_node @sexp, value: true
  if @sexp.type == :program
    uncond_instruct @current_return
  else
    return_uncond_jump_instruct result
  end
  
  @graph.prune_totally_useless_blocks
  @graph
end

- (Object) build_block_with_jump(target = nil, name = nil)

Creates a new block that jumps to the given target upon completion. Very useful for building branches.



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 262

def build_block_with_jump(target = nil, name = nil)
  new_block = name ? create_block(name) : create_block
  with_current_basic_block(new_block) do
    yield
    uncond_instruct target if target
  end
  new_block
end

- (Object) build_exception_blocks 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 102

def build_exception_blocks
  @return_register = create_temporary('t#return_value')
  @graph.final_return    = create_temporary('t#final_return')
  @exception_register    = create_temporary('t#exception_value')
  @graph.final_exception = create_temporary('t#exit_exception')
  @current_return = create_block(ControlFlowGraph::RETURN_POSTDOMINATOR_NAME)
  @current_rescue = create_block(ControlFlowGraph::EXCEPTION_POSTDOMINATOR_NAME)
  @current_yield_fail = create_block(ControlFlowGraph::YIELD_POSTDOMINATOR_NAME)
  joined = create_block(ControlFlowGraph::FAILURE_POSTDOMINATOR_NAME)
  with_current_basic_block(@current_rescue) do
    uncond_instruct joined, flags: RGL::ControlFlowGraph::EDGE_ABNORMAL
  end
  with_current_basic_block(@current_yield_fail) do
    uncond_instruct joined, flags: RGL::ControlFlowGraph::EDGE_ABNORMAL
  end
  with_current_basic_block(joined) do
    copy_instruct(@graph.final_exception, @exception_register)
    add_instruction(:raise, @graph.final_exception)
    uncond_instruct @exit, flags: RGL::ControlFlowGraph::EDGE_ABNORMAL, jump_instruct: false
  end
  with_current_basic_block(@current_return) do
    copy_instruct(@graph.final_return, @return_register)
    add_instruction(:return, @graph.final_return)
    uncond_instruct @exit, jump_instruct: false
  end
end

- (Object) build_formal_args(formals, opts = {}) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 179

def build_formal_args(formals, opts={})
  formals.each { |formal| current_scope.add_binding!(formal) }

  nb_formals = formals.last.is_block? ? formals[0..-2] : formals
  has_rest  = rest_arg = nb_formals.find(&:is_rest?)
  min_arity = nb_formals.count(&:is_positional?)
  optionals = nb_formals.select(&:is_optional?)
  num_optionals = optionals.size
  min_nonrest_arity = min_arity + num_optionals
  # zero dynamic args = easy and more efficient case
  if !rest_arg && optionals.empty?
    copy_positionals(nb_formals)
  else
    # pre-dynamic positionals
    cur_arity = call_instruct(ClassRegistry['Laser#Magic'].binding,
        :current_arity, value: true, raise: false)
    pre_dynamic_positional = nb_formals.take_while(&:is_positional?)
    num_pre_dynamics = pre_dynamic_positional.size
    copy_positionals(pre_dynamic_positional)
    # optional args
    previous_optional_block = nil
    optionals.each_with_index do |argument, index|
      max_arity_indicating_missing = const_instruct(index + min_arity)
      has_arg, no_arg = create_blocks 2
      if previous_optional_block
        with_current_basic_block(previous_optional_block) do
          uncond_instruct no_arg
        end
      end
      cond_result = call_instruct(cur_arity, :<, max_arity_indicating_missing,
                                  value: true, raise: false)
      cond_instruct cond_result, no_arg, has_arg
      
      start_block no_arg
      arg_value = walk_node(argument.default_value_sexp, value: true)
      copy_instruct(argument, arg_value)
      previous_optional_block = @current_block
      
      start_block has_arg
      copy_instruct(argument, formal_arg_at(const_instruct(index + num_pre_dynamics)))
    end
    
    optionals_done = create_block
    # rest args
    if has_rest
      rest_start = const_instruct(num_pre_dynamics + num_optionals)
      rest_size = call_instruct(cur_arity, :-, const_instruct(min_nonrest_arity), value: true, raise: false)
      copy_instruct(rest_arg, formal_arg_range(rest_start, rest_size))
    end
    uncond_instruct optionals_done

    if previous_optional_block
      with_current_basic_block(previous_optional_block) do
        # at this point, if there was a rest arg, it's empty.
        if has_rest
          empty_rest = call_instruct(ClassRegistry['Array'].binding, :[], value: true, raise: false)
          copy_instruct(rest_arg, empty_rest)
        end
        uncond_instruct optionals_done
      end
    end
    start_block optionals_done

    # post-dynamic conditionals
    post_dynamic_positional = nb_formals[num_pre_dynamics..-1].select(&:is_positional?)
    post_dynamic_start = call_instruct(cur_arity, :-,
        const_instruct(post_dynamic_positional.size), value: true, raise: false)
    copy_positionals_with_offset(post_dynamic_positional, post_dynamic_start)
  end
  block_arg = formals.find(&:is_block?)
  if block_arg
    if opts[:block_arg]
      the_block = opts[:block_arg]
    else
      the_block = call_instruct(ClassRegistry['Laser#Magic'].binding,
          :current_block, value: true, raise: false)
    end
    copy_instruct(block_arg, the_block)
  end
end

- (Object) build_prologue 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 134

def build_prologue
  uncond_instruct create_block
  if @sexp.type == :program
    push_self(Scope::GlobalScope.self_ptr)
  else
    push_self(query_self)
  end
  reset_visibility_stack
  build_exception_blocks
  if @sexp.type != :program
    dynamic_context = ClosedScope.new(current_scope, current_self)
    @scope_stack = [dynamic_context]
    @block_arg = call_instruct(ClassRegistry['Laser#Magic'].binding,
        :current_block, value: true, raise: false)
    @block_arg.name = 't#current_block'
    @graph.block_register = @block_arg
    reobserve_current_exception
    build_formal_args(@formals, block_arg: @block_arg) unless @formals.empty?
  end
end

- (Object) copy_positionals(args) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 165

def copy_positionals(args)
  args.each_with_index do |pos, idx|
    copy_instruct(pos, formal_arg_at(const_instruct(idx)))
  end
end

- (Object) copy_positionals_with_offset(args, offset) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 171

def copy_positionals_with_offset(args, offset)
  args.each_with_index do |pos, idx|
    dynamic_idx = idx.zero? ? offset : call_instruct(const_instruct(idx), :+, offset,
        value: true, raise: false)
    copy_instruct(pos, formal_arg_at(dynamic_idx))
  end
end

- (Object) current_namespace 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 39

def current_namespace
  scope = current_scope
  scope = scope.parent if @scope_stack.size == 1 && @sexp.type != :program
  scope.lexical_target
end

- (Object) current_scope 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 49

def current_scope
  @scope_stack.last
end

- (Object) current_self 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 69

def current_self
  @self_stack.last
end

- (Object) formal_arg_at(idx) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 160

def formal_arg_at(idx)
  call_instruct(ClassRegistry['Laser#Magic'].binding, :current_argument, idx,
      value: true, raise: false)
end

- (Object) formal_arg_range(start, size) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 155

def formal_arg_range(start, size)
  call_instruct(ClassRegistry['Laser#Magic'].binding, :current_argument_range,
      start, size, value: true, raise: false)
end

- (Object) novalue_walk(node)

Walks the node expecting that the expression's return value will be discarded. Since everything is an expression in Ruby, knowing when to ignore return values is nice.



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 461

def novalue_walk(node)
  with_current_node(node) do
    case node.type
    when :void_stmt
      # Do nothing.
    when :massign
      lhs, rhs = node.children
      multiple_assign_instruct(lhs, rhs, value: false)
    when :opassign
      lhs, op, rhs = node.children
      op = op.expanded_identifier[0..-2].to_sym
      if lhs.type == :field
        receiver = walk_node lhs[1], value: true
        method_name = lhs[3].expanded_identifier
        # Receiver is ONLY EVALUATED ONCE
        # (on ruby 1.9.2p136 (2010-12-25 revision 30365) [x86_64-darwin10.6.0])
        current_val = call_instruct(receiver, method_name.to_sym, block: false, value: true)
        if op == :||"
          false_block, after = create_blocks 2
          cond_instruct(current_val, after, false_block)

          start_block false_block
          rhs_value = walk_node rhs, value: true
          call_instruct(receiver, "#{method_name}=".to_sym, rhs_value, block: false, value: false)
          uncond_instruct after
        
          start_block after
        elsif op == :&&"
          true_block, after = create_blocks 2
          cond_instruct(current_val, true_block, after)

          start_block true_block
          rhs_value = walk_node rhs, value: true
          call_instruct(receiver, "#{method_name}=".to_sym, rhs_value, block: false, value: false)
          uncond_instruct after
        
          start_block after
        else
          rhs_value = walk_node rhs, value: true
          temp_result = call_instruct(current_val, op, rhs_value, block: false, value: true)
          call_instruct(receiver, "#{method_name}=".to_sym, temp_result, block: false, value: false)
        end
      # TODO(adgar): aref_field
      else
        result = binary_instruct(lhs, op, rhs, value: true)
        single_assign_instruct(lhs, result)
      end
    when :case
      after = create_block
      argument, body = node.children
      argument_value = walk_node argument, value: true
    
      while body && body.type == :when
        when_opts, when_body, body = body.children
        when_body_block = create_block
        when_opts.each do |opt|
          after_fail = create_block
          condition_result = call_instruct(walk_node(opt, value: true), :===, argument_value, value: true)
          cond_instruct(condition_result, when_body_block, after_fail)
          start_block after_fail
        end
        all_fail = @current_block

        start_block when_body_block
        walk_body when_body, value: false
        uncond_instruct after
      
        start_block all_fail
      end
      if body && body.type == :else
        walk_body body[1], value: false
      end
      uncond_instruct after
    when :var_ref
      nil
    when :for
      lhs, receiver, body = node.children
      receiver_value = walk_node receiver, value: true
      if Symbol === lhs[0]
        # field or var_ref/const_ref
        case lhs.type
        when :field
          # TODO(adgar): generate calls
        else
          # just get the value
          arg_bindings = [lhs.binding]
          call_method_with_block(receiver_value, :each, [], arg_bindings, body, value: false)
        end
      else
        # TODO(adgar): multiple assign
      end
    when :string_embexpr
      node[1].each { |elt| walk_node(elt, value: false) }
    when :@CHAR, :@tstring_content, :@int, :@float, :@regexp_end, :symbol,
         :@label, :symbol_literal, :defined
      # do nothing
    when :string_literal
      content_nodes = node[1].children
      content_nodes.each do |node|
        walk_node node, value: false
      end
    when :xstring_literal
      body = build_string_instruct(node[1])
      call_instruct(self_register, :`, body, value: false)
    when :regexp_literal
      node[1].each { |part| walk_node node, value: false }
    when :dyna_symbol
      content_nodes = node[1].children
      content_nodes.each { |node| walk_node node, value: false }
    when :array
      receiver = ClassRegistry['Array'].binding
      generic_call_instruct(receiver, :[], node[1], false, value: false)
    when :hash
      if node[1]
        walk_node node[1], value: false
      else
        const_instruct({}, value: false)
      end
    when :assoclist_from_args, :bare_assoc_hash
      pairs = node[1]
      key_value_paired = pairs.map {|a, b| [walk_node(a, value: true), walk_node(b, value: true)] }.flatten
      receiver = ClassRegistry['Hash'].binding
      call_instruct(receiver, :[], *key_value_paired, block: false, value: false, raise: false)
    else
      raise ArgumentError.new("Unknown AST node type #{node.type.inspect}")
    end
  end
end

- (Object) observe_just_raised_exception 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 96

def observe_just_raised_exception
  cur_exception = call_instruct(ClassRegistry['Laser#Magic'].binding,
      :get_just_raised_exception, value: true, raise: false)
  copy_instruct(@exception_register, cur_exception)
end

- (Object) pop_scope 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 53

def pop_scope
  @scope_stack.pop
end

- (Object) pop_self 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 73

def pop_self
  @self_stack.pop
  copy_instruct(@self_register, current_self)
end

- (Object) push_scope(scope) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 45

def push_scope(scope)
  @scope_stack.push scope
end

- (Object) push_self(obj) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 64

def push_self(obj)
  copy_instruct(@self_register, obj)
  @self_stack.push obj
end

- (Object) query_self 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 85

def query_self
  call_instruct(ClassRegistry['Laser#Magic'].binding,
      :current_self, value: true, raise: false)
end

- (Object) reobserve_current_exception 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 90

def reobserve_current_exception
  cur_exception = call_instruct(ClassRegistry['Laser#Magic'].binding,
      :current_exception, value: true, raise: false)
  copy_instruct(@exception_register, cur_exception)
end

- (Object) reset_visibility_stack 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 129

def reset_visibility_stack
  initial = call_instruct(ClassRegistry['Array'].binding, :[], const_instruct(:private), value: true, raise: false)
  copy_instruct(Bootstrap::VISIBILITY_STACK, initial)
end

- (Object) value_walk(node)

Walks the node with the expectation that the return value will be used.



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 591

def value_walk(node)
  with_current_node(node) do
    case node.type
    when :opassign
      lhs, op, rhs = node.children
      op = op.expanded_identifier[0..-2].to_sym
      if lhs.type == :field
        receiver = walk_node lhs[1], value: true
        method_name = lhs[3].expanded_identifier
        # Receiver is ONLY EVALUATED ONCE
        # (on ruby 1.9.2p136 (2010-12-25 revision 30365) [x86_64-darwin10.6.0])
        current_val = call_instruct(receiver, method_name.to_sym, block: false, value: true)
        if op == :||"
          result = create_temporary
          true_block, false_block, after = create_blocks 3
          cond_instruct(current_val, true_block, false_block)

          start_block true_block
          copy_instruct result, current_val
          uncond_instruct after

          start_block false_block
          rhs_value = walk_node rhs, value: true
          call_instruct(receiver, "#{method_name}=".to_sym, rhs_value, block: false, value: false)
          copy_instruct result, rhs_value
          uncond_instruct after
        
          start_block after
          result
        elsif op == :&&"
          result = create_temporary
          true_block, false_block, after = create_blocks 3
          cond_instruct(current_val, true_block, false_block)

          start_block true_block
          rhs_value = walk_node rhs, value: true
          call_instruct(receiver, "#{method_name}=".to_sym, rhs_value, block: false, value: false)
          copy_instruct result, rhs_value
          uncond_instruct after

          start_block false_block
          copy_instruct result, current_val
          uncond_instruct after
        
          start_block after
          result
        else
          rhs_value = walk_node rhs, value: true
          temp_result = call_instruct(current_val, op, rhs_value, block: false, value: true)
          call_instruct(receiver, "#{method_name}=".to_sym, temp_result, block: false, value: false)
          temp_result
        end
      # TODO(adgar): aref_field
      else
        result = binary_instruct(lhs, op, rhs, value: true)
        single_assign_instruct(lhs, result)
        result
      end
    when :var_field
      variable_instruct(node)
    when :var_ref
      if node[1].type == :@const
        const_lookup(node[1].expanded_identifier)
      elsif node[1].type == :@ident || node[1].expanded_identifier == 'self'
        variable_instruct(node)
      elsif node[1].type == :@kw
        const_instruct(node.constant_value)
      elsif node[1].type == :@ivar
        call_instruct(current_self, :instance_variable_get,
            const_instruct(node.expanded_identifier), value: true, ignore_privacy: true)
      elsif node[1].type == :@gvar
        call_instruct(ClassRegistry['Laser#Magic'].binding, :get_global,
            const_instruct(node.expanded_identifier), raise: false, value: true)
      end
    when :top_const_ref
      const = node[1]
      ident = const_instruct(const.expanded_identifier)
      call_instruct(ClassRegistry['Object'].binding,
          :const_get, ident, value: true)
    when :for
      lhs, receiver, body = node.children
      receiver_value = walk_node receiver, value: true
      if Symbol === lhs[0]
        # field or var_ref/const_ref
        case lhs.type
        when :field
          # call
        else
          # just get the value
          arg_bindings = [lhs.binding]
          call_method_with_block(receiver_value, :each, [], arg_bindings, body, value: true)
        end
      # TODO(adgar): aref_field
      else
        # TODO(adgar): multiple assign
      end
    when :case
      after = create_block
      result = create_temporary
      argument, body = node.children
      argument_value = walk_node argument, value: true
    
      while body && body.type == :when
        when_opts, when_body, body = body.children
        when_body_block = create_block
        when_opts.each do |opt|
          after_fail = create_block
          condition_result = call_instruct(walk_node(opt, value: true), :===, argument_value, value: true)
          cond_instruct(condition_result, when_body_block, after_fail)
          start_block after_fail
        end
        all_fail = @current_block

        start_block when_body_block
        when_body_result = walk_body when_body, value: true
        copy_instruct(result, when_body_result)
        uncond_instruct after
      
        start_block all_fail
      end
      if body.nil?
        copy_instruct(result, nil)
        uncond_instruct after
      elsif body.type == :else
        else_body_result = walk_body body[1], value: true
        copy_instruct(result, else_body_result)
        uncond_instruct after
      end
      
      start_block after
      result
    when :@CHAR, :@tstring_content, :@int, :@float, :@regexp_end, :symbol,
         :@label, :symbol_literal
      const_instruct(node.constant_value)
    when :string_literal
      content_nodes = node[1].children
      build_string_instruct(content_nodes)
    when :string_embexpr
      final = walk_body node[1], value: true
      call_instruct(final, :to_s, value: true)
    when :xstring_literal
      body = build_string_instruct(node[1])
      call_instruct(self_register, :`, body, value: true)
    when :regexp_literal
      body = build_string_instruct(node[1])
      options = const_instruct(node[2].constant_value)
      receiver = ClassRegistry['Regexp'].binding
      call_instruct(receiver, :new, body, options, value: true)
    when :dyna_symbol
      content_nodes = node[1].children
      string_version = build_string_instruct(content_nodes)
      call_instruct(string_version, :to_sym, value: true, raise: false)
    when :array
      receiver = ClassRegistry['Array'].binding
      generic_call_instruct(receiver, :[], node[1], false, value: true)
    when :hash
      if node[1]
        walk_node node[1], value: true
      else
        const_instruct({})
      end
    when :assoclist_from_args, :bare_assoc_hash
      pairs = node[1].map { |_, k, v| [k, v] }
      key_value_paired = pairs.map {|a, b| [walk_node(a, value: true), walk_node(b, value: true)] }.flatten
      receiver = ClassRegistry['Hash'].binding
      call_instruct(receiver, :[], *key_value_paired, block: false, value: true)
    when :defined
      defined_op_instruct(node[1])
    else
      raise ArgumentError.new("Unknown AST node type #{node.type.inspect}")
    end
  end
end

- (Object) walk_node(node, opts = {})

Walks the node differently based on whether the value is needed.



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 290

def walk_node(node, opts={})
  with_current_node(node) do
    case node.type
    when :bodystmt
      bodystmt_walk node
    when :class
      class_name, superclass, body = node.children
      class_instruct(class_name, superclass, body, opts)
    when :module
      module_name, body = node.children
      module_instruct(module_name, body, opts)
    when :sclass
      receiver, body = node.children
      singleton_class_instruct receiver, body, opts
    when :def
      name, args, body = node.children
      name = const_instruct(name.expanded_identifier.to_sym)
      parsed_args = Signature.arg_list_for_arglist(args)
      def_opts =  opts.merge(line_number: node.line_number)
      def_instruct(current_namespace, name, parsed_args, body, def_opts)
    when :defs
      recv, _, name, args, body = node.children
      name = const_instruct(name.expanded_identifier.to_sym)
      receiver = walk_node(recv, value: true)
      singleton = call_instruct(receiver, :singleton_class, value: true)
      parsed_args = Signature.arg_list_for_arglist(args)
      def_opts =  opts.merge(line_number: node.line_number)
      def_instruct(singleton, name, parsed_args, body, def_opts)
    when :alias
      lhs, rhs = node.children
      lhs_val = const_instruct(lhs[1].expanded_identifier.to_sym)
      rhs_val = const_instruct(rhs[1].expanded_identifier.to_sym)
      call_instruct(current_namespace, :alias_method, lhs_val, rhs_val,
                    value: false, ignore_privacy: true)
    when :undef
      undeffed = node.children.first
      undeffed.each do |method|
        method_name = const_instruct(method[1].expanded_identifier.to_sym)
        call_instruct(current_namespace, :undef_method, method_name,
            value: false, raise: true)
      end
      nil
    when :assign
      lhs, rhs = node.children
      single_assign_instruct(lhs, rhs, opts)
    when :massign
      lhs, rhs = node.children
      multiple_assign_instruct(lhs, rhs, opts)
    when :begin
      walk_node node[1], opts
    when :paren
      walk_body node[1], opts
    when :while
      condition, body = node.children
      while_instruct(condition, body, opts)
    when :while_mod
      condition, body_stmt = node.children
      while_instruct(condition, [body_stmt], opts)
    when :until
      condition, body = node.children
      until_instruct(condition, body, opts)
    when :until_mod
      condition, body_stmt = node.children
      until_instruct(condition, [body_stmt], opts)
    when :if
      if_instruct(node, false, opts)
    when :unless
      condition, body, else_block = node.children
      unless_instruct(condition, body, else_block, opts)
    when :if_mod
      if_instruct(node, true, opts)
    when :unless_mod
      condition, body = node.children
      unless_instruct(condition, [body], nil, opts)
    when :rescue_mod
      rescue_expr, guarded_expr = node.children
      rescue_mod_instruct(rescue_expr, guarded_expr, opts)
    when :unary
      op, receiver = node.children
      receiver = walk_node(receiver, value: true)
      call_instruct(receiver, op, opts)
    when :binary
      # If someone makes an overloaded operator that mutates something....
      # we have to run it (maybe), even if we hate them.
      lhs, op, rhs = node.children
      binary_instruct(lhs, op, rhs, opts)
    when :ifop
      cond, if_true, if_false = node.children
      ternary_instruct(cond, if_true, if_false, opts)
    when :const_path_ref
      lhs, const = node.children
      lhs_value = walk_node lhs, value: true
      ident = const_instruct(const.expanded_identifier)
      call_instruct(lhs_value, :const_get, ident, opts)
    when :call, :command, :command_call, :aref, :method_add_arg, :vcall
      issue_call node, opts
    when :method_add_block
      # need: the receiver, the method name, the arguments, and the block body
      method_call = node.method_call
      receiver = if method_call.receiver_node
                 then walk_node(method_call.receiver_node, value: true)
                 else self_instruct
                 end
      arg_node = method_call.arg_node
      arg_node = arg_node[1] if arg_node && arg_node.type == :arg_paren
      block_arg_bindings = node[2][1] ? Signature.arg_list_for_arglist(node[2][1][1]) : []
      body_sexp = node[2][2]
      case node[1].type
      when :super
        arg_node = arg_node[1] if arg_node.type == :args_add_block
        call_method_with_block(
            receiver, method_call.method_name, arg_node,
            block_arg_bindings, body_sexp, opts)
      when :zsuper
        call_zsuper_with_block(node[1], block_arg_bindings, body_sexp, opts)
      else
        opts = opts.merge(ignore_privacy: true) if method_call.implicit_receiver?
        call_method_with_block(
            receiver, method_call.method_name, arg_node, block_arg_bindings, body_sexp, opts)
      end
    when :super
      issue_super_call(node)
    when :zsuper
      # TODO(adgar): blocks in args & style
      block = rb_check_convert_type(@block_arg, ClassRegistry['Proc'].binding, :to_proc)
      invoke_super_with_block(*compute_zsuper_arguments, block, opts)
    when :yield
      yield_instruct(node[1], opts)
    when :yield0
      yield_instruct(nil, opts)
    when :return
      return_instruct node
      const_instruct(nil) if opts[:value]
    when :return0
      return0_instruct
      const_instruct(nil) if opts[:value]
    when :break
      break_instruct(node[1])
      const_instruct(nil) if opts[:value]
    when :next
      next_instruct(node[1])
      const_instruct(nil) if opts[:value]
    when :redo
      redo_instruct
      const_instruct(nil) if opts[:value]
    when :void_stmt
      const_instruct(nil) if opts[:value]
    when :program
      uncond_instruct create_block
      walk_body node[1], value: false
    when :dot3
      start, stop = node.children
      start_val = walk_node(start, value: true)
      stop_val = walk_node(stop, value: true)
      true_val = const_instruct(true)
      call_instruct(ClassRegistry['Range'].binding, :new, start_val, stop_val, true_val, opts)
    when :dot2
      start, stop = node.children
      start_val = walk_node(start, value: true)
      stop_val = walk_node(stop, value: true)
      false_val = const_instruct(false)
      call_instruct(ClassRegistry['Range'].binding, :new, start_val, stop_val, false_val, opts)
    else
      opts[:value] ? value_walk(node) : novalue_walk(node)
    end
  end
end

- (Object) with_current_basic_block(basic_block)

yields with the current basic block set to the provided basic block. useful for quickly adding an edge without directly touching the graph object.



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 274

def with_current_basic_block(basic_block)
  old_block, @current_block = @current_block, basic_block
  yield
ensure
  @current_block = old_block
end

- (Object) with_current_node(node) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 281

def with_current_node(node)
  old_node, @current_node = @current_node, node
  @current_node.scope = current_scope
  yield
ensure
  @current_node = old_node
end

- (Object) with_scope(scope) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 57

def with_scope(scope)
  push_scope scope
  yield
ensure
  pop_scope
end

- (Object) with_self(namespace) 



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# File 'lib/laser/analysis/control_flow/cfg_builder.rb', line 78

def with_self(namespace)
  push_self namespace
  yield
ensure
  pop_self
end