transforms/unroll_loop: do not unroll breakable loops

artiq/transforms/unroll_loops.py

@@ -14,6 +14,24 @@ def _count_stmts(node):
         return 1
 
 
+def _loop_breakable(node):
+    if isinstance(node, ast.Break):
+        return 1
+    elif isinstance(node, ast.Return):
+        return 2
+    elif isinstance(node, list):
+        return max(map(_loop_breakable, node), default=0)
+    elif isinstance(node, ast.If):
+        return max(_loop_breakable(node.body), _loop_breakable(node.orelse))
+    elif isinstance(node, (ast.For, ast.While)):
+        bb = _loop_breakable(node.body)
+        if bb == 1:
+            bb = 0
+        return max(bb, _loop_breakable(node.orelse))
+    else:
+        return 0
+
+
 class _LoopUnroller(ast.NodeTransformer):
     def __init__(self, limit):
         self.limit = limit
@@ -26,8 +44,8 @@ class _LoopUnroller(ast.NodeTransformer):
             return node
         l_it = len(it)
         if l_it:
-            n = l_it*_count_stmts(node.body)
+            if (not _loop_breakable(node.body)
-            if n < self.limit:
+                    and l_it*_count_stmts(node.body) < self.limit):
                 replacement = []
                 for i in it:
                     if not isinstance(i, int):