Several more code output optimizations done.
This commit is contained in:
Jennifer Taylor
parent
44b3628a85
commit
eddb8dc208
@ -1057,7 +1057,7 @@ class BitVector:
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class ByteCodeDecompiler(VerboseOutput):
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def __init__(self, bytecode: ByteCode, optimize: bool = False) -> None:
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def __init__(self, bytecode: ByteCode, optimize: bool = True) -> None:
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super().__init__()
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self.bytecode = bytecode
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@ -3015,6 +3015,89 @@ class ByteCodeDecompiler(VerboseOutput):
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return statements
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def __remove_goto_return(self, statements: Sequence[Statement]) -> Tuple[List[Statement], bool]:
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# Go through and find labels that point at returns, convert any gotos pointing
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# at them to returns.
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def find_labels(statements: Sequence[Statement], next_statement: Optional[Statement]) -> Set[int]:
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labels: Set[int] = set()
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for i in range(len(statements)):
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cur_statement = statements[i]
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next_statement = statements[i + 1] if (i < len(statements) - 1) else next_statement
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if (
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isinstance(cur_statement, DefineLabelStatement) and
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isinstance(next_statement, NullReturnStatement)
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):
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labels.add(cur_statement.location)
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elif isinstance(cur_statement, DoWhileStatement):
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labels.update(find_labels(cur_statement.body, next_statement))
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elif isinstance(cur_statement, IfStatement):
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labels.update(find_labels(cur_statement.true_statements, next_statement))
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labels.update(find_labels(cur_statement.false_statements, next_statement))
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return labels
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labels = find_labels(statements, None)
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updated: bool = False
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def update_gotos(statement: Statement) -> Statement:
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nonlocal updated
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if isinstance(statement, GotoStatement):
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if statement.location in labels:
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return NullReturnStatement()
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updated = True
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return statement
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statements = self.__walk(statements, update_gotos)
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return statements, updated
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def __eliminate_useless_returns(self, statements: Sequence[Statement]) -> Tuple[List[Statement], bool]:
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# Go through and find returns that are on the "last" line. Basically, any
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# return statement where the next return statement is another return statement
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# or the end of a function.
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def find_returns(statements: Sequence[Statement], next_statement: Statement) -> Set[NullReturnStatement]:
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returns: Set[NullReturnStatement] = set()
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for i in range(len(statements)):
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cur_statement = statements[i]
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next_statement = statements[i + 1] if (i < len(statements) - 1) else next_statement
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if (
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isinstance(cur_statement, NullReturnStatement) and
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isinstance(next_statement, NullReturnStatement)
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):
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returns.add(cur_statement)
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elif isinstance(cur_statement, DoWhileStatement):
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returns.update(find_returns(cur_statement.body, next_statement))
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elif isinstance(cur_statement, IfStatement):
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returns.update(find_returns(cur_statement.true_statements, next_statement))
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returns.update(find_returns(cur_statement.false_statements, next_statement))
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return returns
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# Instead of an empty next statement, make up a return so we catch anything
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# without needing multiple conditionals above.
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returns = find_returns(statements, NullReturnStatement())
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updated: bool = False
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def remove_returns(statement: Statement) -> Statement:
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nonlocal updated
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for removable in returns:
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if removable is statement:
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updated = True
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return None
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return statement
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statements = self.__walk(statements, remove_returns)
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return statements, updated
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def __remove_useless_gotos(self, statements: Sequence[Statement]) -> Tuple[List[Statement], bool]:
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# Go through and find gotos that point at the very next line and remove them.
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# This can happen due to the way we analyze if statements.
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@ -3092,33 +3175,49 @@ class ByteCodeDecompiler(VerboseOutput):
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return self.__walk(statements, remove_label), changed
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def __eliminate_useless_control_flows(self, statements: Sequence[Statement]) -> List[Statement]:
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def __eliminate_useless_continues(self, statements: Sequence[Statement]) -> Tuple[List[Statement], bool]:
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# Go through and find continue statements on the last line of a do-while.
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changed: bool = False
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def remove_continue(statement: Statement) -> Optional[Statement]:
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nonlocal changed
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if isinstance(statement, DoWhileStatement):
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if statement.body and isinstance(statement.body[-1], ContinueStatement):
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changed = True
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statement.body.pop()
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return statement
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statements = self.__walk(statements, remove_continue)
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if isinstance(statements[-1], NullReturnStatement):
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return statements[:-1]
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return statements
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return statements, changed
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def __swap_empty_ifs(self, statements: Sequence[Statement]) -> List[Statement]:
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# Go through and find continue statements on the last line of a do-while.
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changed: bool = False
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def swap_empty_ifs(statement: Statement) -> Optional[Statement]:
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nonlocal changed
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if isinstance(statement, IfStatement):
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if statement.false_statements and (not statement.true_statements):
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# Swap this, invert the conditional
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changed = True
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return IfStatement(
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statement.cond.invert(),
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statement.false_statements,
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statement.true_statements,
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)
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elif (not statement.true_statements) and (not statement.false_statements):
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# Drop the if, it has no body.
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changed = True
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return None
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return statement
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return self.__walk(statements, swap_empty_ifs)
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while True:
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changed = False
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statements = self.__walk(statements, swap_empty_ifs)
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if not changed:
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return statements
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def __verify_balanced_labels(self, statements: Sequence[Statement]) -> None:
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gotos: Set[int] = set()
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@ -3199,12 +3298,25 @@ class ByteCodeDecompiler(VerboseOutput):
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# Now, let's do some clean-up passes.
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if self.optimize:
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statements = self.__collapse_identical_labels(statements)
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statements = self.__eliminate_useless_control_flows(statements)
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while True:
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statements, changed1 = self.__eliminate_unused_labels(statements)
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statements, changed2 = self.__remove_useless_gotos(statements)
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any_changed = False
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if not changed1 and not changed2:
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statements, changed = self.__eliminate_useless_continues(statements)
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any_changed = any_changed or changed
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statements, changed = self.__eliminate_unused_labels(statements)
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any_changed = any_changed or changed
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statements, changed = self.__remove_useless_gotos(statements)
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any_changed = any_changed or changed
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statements, changed = self.__remove_goto_return(statements)
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any_changed = any_changed or changed
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statements, changed = self.__eliminate_useless_returns(statements)
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any_changed = any_changed or changed
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if not any_changed:
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break
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statements = self.__swap_empty_ifs(statements)
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@ -663,9 +663,7 @@ class TestAFPDecompile(ExtendedTestCase):
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AP2Action(104, AP2Action.PLAY),
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])
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statements = self.__call_decompile(bytecode)
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# TODO: The output should be optimized to remove redundant return statements.
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self.assertEqual(self.__equiv(statements), ["if (True) {\n builtin_StartPlaying()\n return\n} else {\n builtin_StopPlaying()\n return\n}"])
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self.assertEqual(self.__equiv(statements), ["if (True) {\n builtin_StartPlaying()\n} else {\n builtin_StopPlaying()\n}"])
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def test_if_handling_diamond_return_to_end(self) -> None:
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# If true-false diamond case but the cases never converge.
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@ -747,9 +745,7 @@ class TestAFPDecompile(ExtendedTestCase):
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AP2Action(105, AP2Action.END),
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])
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statements = self.__call_decompile(bytecode)
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# TODO: The output should be optimized to remove redundant return statements.
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self.assertEqual(self.__equiv(statements), ["if (True) {\n builtin_StartPlaying()\n return\n} else {\n builtin_StopPlaying()\n return\n}"])
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self.assertEqual(self.__equiv(statements), ["if (True) {\n builtin_StartPlaying()\n} else {\n builtin_StopPlaying()\n}"])
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def test_if_handling_or(self) -> None:
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# Two ifs that together make an or (if register == 1 or register == 3)
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