compiler: Fix break/continue targets in loop else blocks

Previously, they would still target the respective labels in the
just-exited loop.

Signed-off-by: David Nadlinger <code@klickverbot.at>

artiq/compiler/transforms/artiq_ir_generator.py

@@ -452,6 +452,9 @@ class ARTIQIRGenerator(algorithm.Visitor):
             self.current_block = body
             self.visit(node.body)
             post_body = self.current_block
+        finally:
+            self.break_target = old_break
+            self.continue_target = old_continue
 
         if any(node.orelse):
             else_tail = self.add_block("while.else")
@@ -472,9 +475,6 @@ class ARTIQIRGenerator(algorithm.Visitor):
         if not post_body.is_terminated():
             post_body.append(ir.Branch(head))
         break_block.append(ir.Branch(tail))
-        finally:
-            self.break_target = old_break
-            self.continue_target = old_continue
 
     def iterable_len(self, value, typ=_size_type):
         if builtins.is_listish(value.type):
@@ -541,6 +541,9 @@ class ARTIQIRGenerator(algorithm.Visitor):
                 self.current_assign = None
             self.visit(node.body)
             post_body = self.current_block
+        finally:
+            self.break_target = old_break
+            self.continue_target = old_continue
 
         if any(node.orelse):
             else_tail = self.add_block("for.else")
@@ -564,9 +567,6 @@ class ARTIQIRGenerator(algorithm.Visitor):
         if not post_body.is_terminated():
             post_body.append(ir.Branch(continue_block))
         break_block.append(ir.Branch(tail))
-        finally:
-            self.break_target = old_break
-            self.continue_target = old_continue
 
     def visit_Break(self, node):
         self.append(ir.Branch(self.break_target))

artiq/test/lit/integration/for.py

@@ -27,3 +27,27 @@ for x in range(10):
     assert False
 else:
     assert False
+
+# Verify continue target is reset in else block.
+cond = False
+while True:
+    if cond:
+        break
+    cond = True
+    for _ in range(1):
+        pass
+    else:
+        continue
+    assert False
+else:
+    assert False
+
+# Verify for target is reset in else block.
+while True:
+    for _ in range(1):
+        pass
+    else:
+        break
+    assert False
+else:
+    assert False

artiq/test/lit/integration/while.py

@@ -29,3 +29,27 @@ while cond:
     cond = False
     continue
     assert False
+
+# Verify continue target is reset in else block.
+cond = False
+while True:
+    if cond:
+        break
+    cond = True
+    while False:
+        assert False
+    else:
+        continue
+    assert False
+else:
+    assert False
+
+# Verify break target is reset in else block.
+while True:
+    while False:
+        assert False
+    else:
+        break
+    assert False
+else:
+    assert False