Fix try/finally:while:try compilation

When we have a trys inside a loop then we want to make sure any
finallys are executed by break and continue inside this try. But
this shouldn't pull finallys defined outside the loop in to the
loop. This change resets the `outer_final` attribute when
visiting for and while loops so that this doesn't happen.

Signed-off-by: Michael Birtwell <michael.birtwell@oxionics.com>

artiq/compiler/transforms/artiq_ir_generator.py

@@ -468,6 +468,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             self.append(ir.BranchIf(cond, if_true, tail), block=head)
 
     def visit_While(self, node):
+        old_outer_final, self.outer_final = self.outer_final, None
         try:
             head = self.add_block("while.head")
             self.append(ir.Branch(head))
@@ -487,6 +488,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
         finally:
             self.break_target = old_break
             self.continue_target = old_continue
+            self.outer_final = old_outer_final
 
         if any(node.orelse):
             else_tail = self.add_block("while.else")
@@ -561,6 +563,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             assert False
 
     def visit_ForT(self, node):
+        old_outer_final, self.outer_final = self.outer_final, None
         try:
             iterable = self.visit(node.iter)
             length = self.iterable_len(iterable)
@@ -598,6 +601,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
         finally:
             self.break_target = old_break
             self.continue_target = old_continue
+            self.outer_final = old_outer_final
 
         if any(node.orelse):
             else_tail = self.add_block("for.else")
@@ -783,8 +787,18 @@ class ARTIQIRGenerator(algorithm.Visitor):
             old_unwind, self.unwind_target = self.unwind_target, final_dispatcher
 
         if any(node.finalbody):
+            # if we have a while:try/finally continue must execute finally
+            # before continuing the while
             redirect = final_branch
         elif self.outer_final is not None:
+            # If we have while:try/finally:try then we need to execute that finally
+            # before the continuing the while
+            # If we have try/finally:while:try then we should just continue the
+            # while without having to execute the finally until later
+            # If we have try/finally:while:try/finally:try we should execute
+            # one but not the other
+            # This is achieved by reseting self.outer_final in while and for
+            # loops
             redirect = self.outer_final
         else:
             redirect = lambda dest, proxy: proxy.append(ir.Branch(dest))