Class: Furnace::AVM2::Transform::ASTBuild

Inherits:
Object
  • Object
show all
Defined in:
lib/furnace-avm2/transform/ast_build.rb

Overview

I’m not exactly proud of this code, but it works… for now. I really should rework it if I want to expect it to work good.

Constant Summary collapse

CONDITIONAL_OPERATORS = 
[ :if_eq,  :if_false, :if_true,      :if_ge,        :if_gt,
:if_le,  :if_lt,    :if_ne,        :if_nge,       :if_ngt,
:if_nle, :if_nlt,   :if_strict_eq, :if_strict_ne, :if_true ]
PURE_OPERATORS = 
[ :integer, :double, :string, :false, :true, :nan, :undefined, :null,
:find_property_strict ]
PRE_POST_OPERATORS = 
[ :increment, :increment_i, :decrement, :decrement_i ]
SHORT_ASSIGN_OPERATORS = 
[ :add, :add_i, :subtract, :subtract_i, :multiply, :multiply_i,
:divide, :modulo,
:set_local, :set_local_0, :set_local_1, :set_local_2, :set_local_3,
:new_catch, :new_activation,
:next_value ]
LocalIncDecInnerMatcher = 
AST::Matcher.new do
  [ either[*Furnace::AVM2::Transform::ASTBuild::PRE_POST_OPERATORS],
    either[
      [:convert, any,
        [:get_local, any]],
      [:get_local, any],
    ]
  ]
end

Instance Method Summary collapse

Constructor Details

#initialize(options) ⇒ ASTBuild

Returns a new instance of ASTBuild.



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 21

def initialize(options)
  @validate = options[:validate] || false
  @verbose  = options[:verbose]  || false

  #@verbose = true
end

Instance Method Details

#consume(count) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 28

def consume(count)
  if count == 0
    []
  elsif count <= @stack.size
    @stack.slice!(-count..-1)
  else
    raise "cannot consume #{count}: stack underflow with #{@stack.size}"
  end
end

#emit(node) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 42

def emit(node)
  if @verbose
    puts "emitted:"
    puts node.to_sexp(1)
  end

  @ast.children.push node
end

#expand_conditionals ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 86

def expand_conditionals
  expressions = []

  while @stack.any? && CONDITIONAL_OPERATORS.include?(@stack.last.type)
    conditional, = consume(1)

    jump_node = AST::Node.new(:jump_if, [
      true,
      conditional.metadata[:offset],
      conditional
    ], label: conditional.metadata[:label])

    expressions.unshift jump_node
  end

  expressions.each do |expr|
    emit(expr)
  end
end

#extend_complex_expr(valid_types, expected_depth = nil) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 55

def extend_complex_expr(valid_types, expected_depth=nil)
  expr, current = consume(2)

  if @validate
    if !valid_types.include?(expr.type)
      raise "invalid complex expr: #{expr.type} not in #{valid_types}"
    elsif expected_depth && expr.children.count != expected_depth
      raise "invalid complex expr: depth #{expr.children.count} != #{expected_depth}"
    end
  end

  expr.children << current
  produce(expr)
end

#finalize_complex_expr(opcode, worklist, valid_types, expected_depth = nil, wrap_to = nil) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 70

def finalize_complex_expr(opcode, worklist, valid_types, expected_depth=nil, wrap_to=nil)
  while worklist.last == opcode.offset
    extend_complex_expr(valid_types, expected_depth)

    if wrap_to
      node, *prepend = *wrap_to

      expr, = consume(1)
      expr = AST::Node.new(node, [*prepend, expr])
      produce(expr)
    end

    worklist.pop
  end
end

#produce(what) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 38

def produce(what)
  @stack.push what
end

#transform(code, body) ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 116

def transform(code, body)
  @stack = []
  @ast   = AST::Node.new(:root)

  dup         = nil
  spurious    = 0

  in_shortcut = false
  shortjump   = []
  ternary     = []

  current_handler = nil
  current_finally = nil

  finallies   = {}
  body.exceptions.each_with_index do |exception, index|
    first, second = exception, body.exceptions[index + 1]
    next unless second

    if first.from_offset == second.from_offset &&
          second.to_offset > first.to_offset &&
          first.target_offset > second.from_offset &&
          first.target_offset < second.to_offset &&
          first.to.is_a?(ABC::AS3Jump) &&
          first.to.target.is_a?(ABC::AS3PushByte)
      entry    = first.to.target.next.target
      epilogue = nil

      cursor = entry.next
      while cursor
        if cursor.is_a?(ABC::AS3LookupSwitch) &&
              cursor.body.default_offset == 8 &&
              cursor.body.case_count == 0
          epilogue = cursor
          break
        end

        cursor = cursor.next
      end

      raise "cannot find finally epilogue" if epilogue.nil?

      finallies[first.to_offset] = {
        first_catch:      first,
        second_catch:     second,
        skip_intervals:   [ first.target_offset...second.target_offset,
                            (second.target_offset + 4)...entry.offset ],
        begin_offset:     first.to.offset,
        entry_offset:     entry.offset,
        epilogue_offset:  epilogue.offset,
        end_offset:       epilogue.offset + epilogue.byte_length,
      }
    end
  end

  exceptions  = {}
  body.exceptions.each_with_index do |exception, index|
    next if finallies.find { |k,f| f[:first_catch] == exception }
    exceptions[exception.target_offset] = exception
  end

  code.each do |opcode|
    if @verbose
      puts "================================"
      puts "stack: #{@stack.inspect}"
      puts "shortjump: #{shortjump.inspect} ternary: #{ternary.inspect}"
      puts "opcode: #{opcode.inspect}"
    end

    finalize_complex_expr(opcode, ternary, CONDITIONAL_OPERATORS, nil, [:ternary_if, false])
    finalize_complex_expr(opcode, shortjump, [ :and, :or ], 1)

    if finallies.has_key? opcode.offset
      current_finally = finallies[opcode.offset]
    end

    if current_finally
      if current_finally[:begin_offset] == opcode.offset
        puts "FINALLY: begin" if @verbose
        emit(AST::Node.new(:jump, [ current_finally[:end_offset] ], label: opcode.offset))
        next
      elsif current_finally[:skip_intervals].find { |si| si.include? opcode.offset }
        puts "FINALLY: skip" if @verbose
        next
      elsif current_finally[:epilogue_offset] == opcode.offset
        puts "FINALLY: epilogue" if @verbose
        emit(AST::Node.new(:nop, [], label: opcode.offset))
        @stack.clear
        next
      end
    end

    if exceptions.has_key? opcode.offset
      exception = exceptions[opcode.offset]

      current_handler  = exception
      if exception.variable
        produce(AST::Node.new(:exception_variable, [ exception.variable.to_astlet ]))
      else
        produce(AST::Node.new(:exception_variable))
      end
    end

    if dup == 1 && (opcode.is_a?(ABC::AS3CoerceB) ||
            opcode.is_a?(ABC::AS3IfTrue) || opcode.is_a?(ABC::AS3IfFalse))
      in_shortcut  = true
      dup          = false
    end

    if in_shortcut
      if opcode.is_a?(ABC::AS3IfTrue)
        type = :or
      elsif opcode.is_a?(ABC::AS3IfFalse)
        type = :and
      elsif opcode.is_a?(ABC::AS3CoerceB)
        next
      elsif opcode.is_a?(ABC::AS3Pop)
        in_shortcut = false
        next
      elsif opcode.is_a?(ABC::AS3Jump) && opcode.body.jump_offset == 0
        # nop
        next
      else
        raise "invalid shortcut"
      end

      node = AST::Node.new(type, [], label: opcode.offset)
      node.children = consume(1)
      produce(node)

      shortjump.push opcode.target_offset
    elsif opcode.is_a?(ABC::AS3Swap)
      first, second = @stack.pop, @stack.pop
      @stack.push first, second
    elsif opcode.is_a?(ABC::AS3Dup)
      node = @stack.last

      if PURE_OPERATORS.include?(node.type) ||
            (node.type == :get_local && node.children.first == 0)
        dup_node = node.dup
        dup_node.metadata[:label] = opcode.offset
        produce(dup_node)
      else
        dup ||= 0
        dup  += 1
      end
    elsif opcode.is_a?(ABC::AS3Jump)
      if opcode.body.jump_offset == 0
        node = AST::Node.new(:nop, [], label: opcode.offset)
        emit(node)
      elsif opcode.target.is_a? ABC::AS3Throw
        node = AST::Node.new(:throw, [ consume(1) ], label: opcode.offset)
        emit(node)
      elsif @stack.any? && !CONDITIONAL_OPERATORS.include?(@stack.last.type)
        extend_complex_expr(CONDITIONAL_OPERATORS)

        ternary.push opcode.target_offset
      else
        expand_conditionals()

        node = AST::Node.new(opcode.ast_type, opcode.parameters, label: opcode.offset)
        emit(node)
      end
    elsif opcode.is_a?(ABC::ControlTransferOpcode)
      node = AST::Node.new(opcode.ast_type, [], label: opcode.offset)
      node.metadata[:offset] = opcode.target_offset
      node.children = consume(opcode.consumes)
      produce(node)
    else
      node = AST::Node.new(opcode.ast_type, [], label: opcode.offset)

      if dup == 1
        top_opcode, = consume(1)
        found = true

        if PRE_POST_OPERATORS.include?(top_opcode.type)
          top_opcode.update(:"pre_#{top_opcode.type}")
        elsif PRE_POST_OPERATORS.include?(node.type)
          node.update(:"post_#{node.type}")
        elsif SHORT_ASSIGN_OPERATORS.include? top_opcode.type
          # just push it through
        else
          found = false
        end

        if found
          produce(AST::Node.new(:unemit))
          dup = false
        end

        produce(top_opcode)
      end

      if dup
        spurious += 1

        save_node = AST::Node.new(:set_local, [ -spurious, *consume(1) ])
        expand_conditionals()
        emit(save_node)

        (1 + dup).times do
          load_node = AST::Node.new(:get_local, [ -spurious ])
          produce(load_node)
        end

        dup = false
      end

      parameters = consume(opcode.consumes)
      if opcode.consumes_context
        context = opcode.context(consume(opcode.consumes_context))
      end

      node.children.concat context if context
      node.children.concat opcode.parameters
      node.children.concat parameters

      # All opcodes which produce 2 results--that is, dup and swap--
      # are already handled at the top.
      if opcode.produces == 0
        # This was a fallthrough assignment.
        if @stack.any? && @stack.last.type == :unemit
          consume(1) # dump unemit
          produce(node)
          next
        end

        expand_conditionals()

        emit(node)
      elsif opcode.produces == 1
        produce(node)
      end
    end
  end

  if @stack.any?
    raise "nonempty stack on exit"
  end

  [ @ast.normalize_hierarchy!, body, finallies.values ]
end

#unemit ⇒ Object 



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# File 'lib/furnace-avm2/transform/ast_build.rb', line 51

def unemit
  @ast.children.delete(-1)
end