Merge pull request #29 from vitek/unreachable_code

Unreachable code removal

Cython/Compiler/Main.py

@@ -109,6 +109,7 @@ class Context(object):
         from ParseTreeTransforms import ExpandInplaceOperators, ParallelRangeTransform
         from TypeInference import MarkAssignments, MarkOverflowingArithmetic
         from ParseTreeTransforms import AlignFunctionDefinitions, GilCheck
+        from ParseTreeTransforms import RemoveUnreachableCode
         from AnalysedTreeTransforms import AutoTestDictTransform
         from AutoDocTransforms import EmbedSignature
         from Optimize import FlattenInListTransform, SwitchTransform, IterationTransform
@@ -138,6 +139,7 @@ class Context(object):
             ParallelRangeTransform(self),
             MarkClosureVisitor(self),
             _align_function_definitions,
+            RemoveUnreachableCode(self),
             ConstantFolding(),
             FlattenInListTransform(),
             WithTransform(self),

Cython/Compiler/Nodes.py

@@ -128,6 +128,7 @@ class Node(object):
 
     is_name = 0
     is_literal = 0
+    is_terminator = 0
     temps = None
 
     # All descandants should set child_attrs to a list of the attributes
@@ -4049,6 +4050,7 @@ class PassStatNode(StatNode):
 class BreakStatNode(StatNode):
 
     child_attrs = []
+    is_terminator = True
 
     def analyse_expressions(self, env):
         pass
@@ -4063,6 +4065,7 @@ class BreakStatNode(StatNode):
 class ContinueStatNode(StatNode):
 
     child_attrs = []
+    is_terminator = True
 
     def analyse_expressions(self, env):
         pass
@@ -4083,6 +4086,7 @@ class ReturnStatNode(StatNode):
     #  return_type   PyrexType
 
     child_attrs = ["value"]
+    is_terminator = True
 
     def analyse_expressions(self, env):
         return_type = env.return_type
@@ -4156,6 +4160,7 @@ class RaiseStatNode(StatNode):
     #  cause       ExprNode or None
 
     child_attrs = ["exc_type", "exc_value", "exc_tb", "cause"]
+    is_terminator = True
 
     def analyse_expressions(self, env):
         if self.exc_type:
@@ -4250,6 +4255,7 @@ class RaiseStatNode(StatNode):
 class ReraiseStatNode(StatNode):
 
     child_attrs = []
+    is_terminator = True
 
     def analyse_expressions(self, env):
         env.use_utility_code(restore_exception_utility_code)

Cython/Compiler/Options.py

@@ -94,6 +94,10 @@ directive_defaults = {
 
     'warn': None,
     'warn.undeclared': False,
+    'warn.unreachable': True,
+
+# remove unreachable code
+    'remove_unreachable': True,
 
 # test support
     'test_assert_path_exists' : [],

Cython/Compiler/ParseTreeTransforms.py

@@ -1666,6 +1666,43 @@ class AlignFunctionDefinitions(CythonTransform):
         return node
 
 
+class RemoveUnreachableCode(CythonTransform):
+    def visit_Node(self, node):
+        self.visitchildren(node)
+        return node
+
+    def visit_StatListNode(self, node):
+        if not self.current_directives['remove_unreachable']:
+            return node
+        self.visitchildren(node)
+        for idx, stat in enumerate(node.stats):
+            idx += 1
+            if stat.is_terminator:
+                if idx < len(node.stats):
+                    if self.current_directives['warn.unreachable']:
+                        warning(node.stats[idx].pos, "Unreachable code", 2)
+                    node.stats = node.stats[:idx]
+                node.is_terminator = True
+                break
+        return node
+
+    def visit_IfClauseNode(self, node):
+        self.visitchildren(node)
+        if node.body.is_terminator:
+            node.is_terminator = True
+        return node
+
+    def visit_IfStatNode(self, node):
+        self.visitchildren(node)
+        if node.else_clause and node.else_clause.is_terminator:
+            for clause in node.if_clauses:
+                if not clause.is_terminator:
+                    break
+            else:
+                node.is_terminator = True
+        return node
+
+
 class YieldNodeCollector(TreeVisitor):
 
     def __init__(self):

tests/errors/break_outside_loop.pyx

+# cython: remove_unreachable=False
 # mode: error
 
 break
@@ -27,11 +28,11 @@ def bool_result():
 
 
 _ERRORS = u'''
-3:0: break statement not inside loop
-6:4: break statement not inside loop
-9:4: break statement not inside loop
-12:4: break statement not inside loop
-17:5: break statement not inside loop
-21:4: break statement not inside loop
-23:4: break statement not inside loop
+4:0: break statement not inside loop
+7:4: break statement not inside loop
+10:4: break statement not inside loop
+13:4: break statement not inside loop
+18:5: break statement not inside loop
+22:4: break statement not inside loop
+24:4: break statement not inside loop
 '''

tests/errors/continue_outside_loop.pyx

+# cython: remove_unreachable=False
 # mode: error
 
 continue
@@ -26,11 +27,11 @@ def bool_result():
     return True
 
 _ERRORS = u'''
-3:0: continue statement not inside loop
-6:4: continue statement not inside loop
-9:4: continue statement not inside loop
-12:4: continue statement not inside loop
-17:5: continue statement not inside loop
-21:4: continue statement not inside loop
-23:4: continue statement not inside loop
+4:0: continue statement not inside loop
+7:4: continue statement not inside loop
+10:4: continue statement not inside loop
+13:4: continue statement not inside loop
+18:5: continue statement not inside loop
+22:4: continue statement not inside loop
+24:4: continue statement not inside loop
 '''

tests/errors/e_return.pyx

+# cython: remove_unreachable=False
 # mode: error
 
 cdef void g():
@@ -9,7 +10,7 @@ cdef int h():
 	return # error
 	return p # error
 _ERRORS = u"""
-5:17: Return with value in void function
-9:1: Return value required
-10:17: Cannot assign type 'int *' to 'int'
+6:17: Return with value in void function
+10:1: Return value required
+11:17: Cannot assign type 'int *' to 'int'
 """

tests/errors/e_while.pyx

+# cython: remove_unreachable=False
 # mode: error
 
 def f(a, b):
@@ -5,6 +6,6 @@ def f(a, b):
 	break # error
 	continue # error
 _ERRORS = u"""
-5:1: break statement not inside loop
-6:1: continue statement not inside loop
+6:1: break statement not inside loop
+7:1: continue statement not inside loop
 """

tests/errors/nogil.pyx

+# cython: remove_unreachable=False
 # mode: error
 
 cdef object f(object x) nogil:
@@ -92,71 +93,71 @@ def bare_pyvar_name(object x):
 # except these: 29, 34, 44, 56, 58, 60, 62-64
 
 _ERRORS = u"""
-3:5: Function with Python return type cannot be declared nogil
-6:5: Function declared nogil has Python locals or temporaries
-8:6: Assignment of Python object not allowed without gil
-11:5: Discarding owned Python object not allowed without gil
-13:5: Function with Python return type cannot be declared nogil
-17:5: Calling gil-requiring function not allowed without gil
-26:9: Calling gil-requiring function not allowed without gil
-28:12: Assignment of Python object not allowed without gil
-30:8: Discarding owned Python object not allowed without gil
-30:16: Constructing complex number not allowed without gil
-32:8: Backquote expression not allowed without gil
-32:8: Discarding owned Python object not allowed without gil
-32:9: Operation not allowed without gil
-33:15: Assignment of Python object not allowed without gil
-33:15: Operation not allowed without gil
-33:15: Python import not allowed without gil
-34:8: Operation not allowed without gil
-34:13: Python import not allowed without gil
-34:25: Constructing Python list not allowed without gil
-34:25: Operation not allowed without gil
-35:17: Iterating over Python object not allowed without gil
-37:11: Discarding owned Python object not allowed without gil
-37:11: Indexing Python object not allowed without gil
+4:5: Function with Python return type cannot be declared nogil
+7:5: Function declared nogil has Python locals or temporaries
+9:6: Assignment of Python object not allowed without gil
+12:5: Discarding owned Python object not allowed without gil
+14:5: Function with Python return type cannot be declared nogil
+18:5: Calling gil-requiring function not allowed without gil
+27:9: Calling gil-requiring function not allowed without gil
+29:12: Assignment of Python object not allowed without gil
+31:8: Discarding owned Python object not allowed without gil
+31:16: Constructing complex number not allowed without gil
+33:8: Backquote expression not allowed without gil
+33:8: Discarding owned Python object not allowed without gil
+33:9: Operation not allowed without gil
+34:15: Assignment of Python object not allowed without gil
+34:15: Operation not allowed without gil
+34:15: Python import not allowed without gil
+35:8: Operation not allowed without gil
+35:13: Python import not allowed without gil
+35:25: Constructing Python list not allowed without gil
+35:25: Operation not allowed without gil
+36:17: Iterating over Python object not allowed without gil
 38:11: Discarding owned Python object not allowed without gil
-38:11: Slicing Python object not allowed without gil
-39:11: Constructing Python slice object not allowed without gil
+38:11: Indexing Python object not allowed without gil
 39:11: Discarding owned Python object not allowed without gil
-39:11: Indexing Python object not allowed without gil
-39:13: Converting to Python object not allowed without gil
-39:15: Converting to Python object not allowed without gil
-39:17: Converting to Python object not allowed without gil
-40:11: Accessing Python attribute not allowed without gil
+39:11: Slicing Python object not allowed without gil
+40:11: Constructing Python slice object not allowed without gil
 40:11: Discarding owned Python object not allowed without gil
-41:9: Constructing Python tuple not allowed without gil
-41:9: Discarding owned Python object not allowed without gil
-42:8: Constructing Python list not allowed without gil
-42:8: Discarding owned Python object not allowed without gil
-43:8: Constructing Python dict not allowed without gil
+40:11: Indexing Python object not allowed without gil
+40:13: Converting to Python object not allowed without gil
+40:15: Converting to Python object not allowed without gil
+40:17: Converting to Python object not allowed without gil
+41:11: Accessing Python attribute not allowed without gil
+41:11: Discarding owned Python object not allowed without gil
+42:9: Constructing Python tuple not allowed without gil
+42:9: Discarding owned Python object not allowed without gil
+43:8: Constructing Python list not allowed without gil
 43:8: Discarding owned Python object not allowed without gil
-44:12: Discarding owned Python object not allowed without gil
-44:12: Truth-testing Python object not allowed without gil
-45:13: Python type test not allowed without gil
-47:10: Discarding owned Python object not allowed without gil
-47:10: Operation not allowed without gil
-48:8: Discarding owned Python object not allowed without gil
-48:8: Operation not allowed without gil
-49:10: Assignment of Python object not allowed without gil
-49:14: Assignment of Python object not allowed without gil
-50:9: Assignment of Python object not allowed without gil
-50:13: Assignment of Python object not allowed without gil
-50:16: Creating temporary Python reference not allowed without gil
-50:19: Creating temporary Python reference not allowed without gil
-51:11: Assignment of Python object not allowed without gil
-51:11: Indexing Python object not allowed without gil
-52:11: Accessing Python attribute not allowed without gil
+44:8: Constructing Python dict not allowed without gil
+44:8: Discarding owned Python object not allowed without gil
+45:12: Discarding owned Python object not allowed without gil
+45:12: Truth-testing Python object not allowed without gil
+46:13: Python type test not allowed without gil
+48:10: Discarding owned Python object not allowed without gil
+48:10: Operation not allowed without gil
+49:8: Discarding owned Python object not allowed without gil
+49:8: Operation not allowed without gil
+50:10: Assignment of Python object not allowed without gil
+50:14: Assignment of Python object not allowed without gil
+51:9: Assignment of Python object not allowed without gil
+51:13: Assignment of Python object not allowed without gil
+51:16: Creating temporary Python reference not allowed without gil
+51:19: Creating temporary Python reference not allowed without gil
 52:11: Assignment of Python object not allowed without gil
-53:8: Constructing Python tuple not allowed without gil
-53:8: Python print statement not allowed without gil
-54:8: Deleting Python object not allowed without gil
-55:8: Returning Python object not allowed without gil
-56:8: Raising exception not allowed without gil
-57:14: Truth-testing Python object not allowed without gil
-59:17: Truth-testing Python object not allowed without gil
-61:8: For-loop using object bounds or target not allowed without gil
-63:8: Try-except statement not allowed without gil
-67:8: Try-finally statement not allowed without gil
-84:8: For-loop using object bounds or target not allowed without gil
+52:11: Indexing Python object not allowed without gil
+53:11: Accessing Python attribute not allowed without gil
+53:11: Assignment of Python object not allowed without gil
+54:8: Constructing Python tuple not allowed without gil
+54:8: Python print statement not allowed without gil
+55:8: Deleting Python object not allowed without gil
+56:8: Returning Python object not allowed without gil
+57:8: Raising exception not allowed without gil
+58:14: Truth-testing Python object not allowed without gil
+60:17: Truth-testing Python object not allowed without gil
+62:8: For-loop using object bounds or target not allowed without gil
+64:8: Try-except statement not allowed without gil
+68:8: Try-finally statement not allowed without gil
+85:8: For-loop using object bounds or target not allowed without gil
 """

tests/errors/return_outside_function_T135.pyx

+# cython: remove_unreachable=False
 # ticket: 135
 # mode: error
 
@@ -31,13 +32,13 @@ else:
 
 
 _ERRORS = u'''
-7:0: Return not inside a function body
-10:4: Return not inside a function body
-13:4: Return not inside a function body
-15:5: Return not inside a function body
-18:5: Return not inside a function body
-22:4: Return not inside a function body
-25:4: Return not inside a function body
-28:4: Return not inside a function body
-30:4: Return not inside a function body
+8:0: Return not inside a function body
+11:4: Return not inside a function body
+14:4: Return not inside a function body
+16:5: Return not inside a function body
+19:5: Return not inside a function body
+23:4: Return not inside a function body
+26:4: Return not inside a function body
+29:4: Return not inside a function body
+31:4: Return not inside a function body
 '''

tests/errors/w_unreachable.pyx

+# mode: error
+# tag: werror
+
+def simple_return():
+    return
+    print 'Where am I?'
+
+def simple_loops(*args):
+    for i in args:
+        continue
+        print 'Never be here'
+
+    while True:
+        break
+        print 'Never be here'
+
+def conditional(a, b):
+    if a:
+        return 1
+    elif b:
+        return 2
+    else:
+        return 3
+    print 'oops'
+
+_ERRORS = """
+6:4: Unreachable code
+11:8: Unreachable code
+15:8: Unreachable code
+24:4: Unreachable code
+"""