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[*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.



21
22
23
24
25
26
 
# 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 



28
29
30
31
32
33
34
35
36
 
# 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 



42
43
44
45
46
47
48
49
 
# 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 



86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
 
# 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 



55
56
57
58
59
60
61
62
63
64
65
66
67
68
 
# 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 



70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
 
# 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 



38
39
40
 
# File 'lib/furnace-avm2/transform/ast_build.rb', line 38

def produce(what)
  @stack.push what
end

#transform(code, body) ⇒ Object 



116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
 
# 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()

        # Spec does not require stack to be empty upon encountering return.
        # If there's something left, it should have been here.
        if opcode.is_a? ABC::FunctionReturnOpcode
          while @stack.any?
            emit(*consume(1))
          end
        end

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

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

#unemit ⇒ Object 



51
52
53
 
# File 'lib/furnace-avm2/transform/ast_build.rb', line 51

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