RemoveUnreachableCode transform and is_terminator Node flag

Cython/Compiler/Nodes.py

@@ -129,6 +129,7 @@ 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
@@ -4050,6 +4051,7 @@ class PassStatNode(StatNode):
 class BreakStatNode(StatNode):
 
     child_attrs = []
+    is_terminator = True
 
     def analyse_expressions(self, env):
         pass
@@ -4064,6 +4066,7 @@ class BreakStatNode(StatNode):
 class ContinueStatNode(StatNode):
 
     child_attrs = []
+    is_terminator = True
 
     def analyse_expressions(self, env):
         pass
@@ -4084,6 +4087,7 @@ class ReturnStatNode(StatNode):
     #  return_type   PyrexType
 
     child_attrs = ["value"]
+    is_terminator = True
 
     def analyse_expressions(self, env):
         return_type = env.return_type
@@ -4157,6 +4161,7 @@ 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:
@@ -4251,6 +4256,7 @@ 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/ParseTreeTransforms.py

@@ -1407,6 +1407,43 @@ 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):