[Dynamic-to-Static] Remove unnecessary variables of the arguments in true_func/false_func (#28722)

python/paddle/fluid/dygraph/dygraph_to_static/ifelse_transformer.py

@@ -245,23 +245,51 @@ def get_name_ids(nodes, end_node=None):
     return name_visitor.name_ids
 
 
-def parse_cond_args(var_ids_dict, return_ids=None, ctx=gast.Load):
+def parse_cond_args(parent_ids_dict,
+                    var_ids_dict,
+                    modified_ids_dict=None,
+                    ctx=gast.Load):
     """
     Find out the ast.Name.id list of input by analyzing node's AST information.
     """
 
-    name_ids = [
+    # 1. filter the var fit the ctx
+    arg_name_ids = [
         var_id for var_id, var_ctx in six.iteritems(var_ids_dict)
         if isinstance(var_ctx[0], ctx)
     ]
-    if return_ids:
-        new_args = set(return_ids) - set(name_ids)
-        name_ids.extend(list(new_args))
-    name_ids.sort()
+
+    # 2. args should contain modified var ids in if-body or else-body
+    #  case:
+    #
+    #   ```
+    #   if b < 1:
+    #     z = y
+    #   else:
+    #     z = x
+    #   ```
+    #
+    #   In the above case, `z` should be in the args of cond()
+    if modified_ids_dict:
+        arg_name_ids = set(arg_name_ids) | set(modified_ids_dict)
+
+    # 3. args should not contain the vars not in parent ids
+    #  case :
+    #
+    #   ```
+    #   x = 1
+    #   if x > y:
+    #     z = [v for v in range(i)]
+    #   ```
+    #
+    #   In the above case, `v` should not be in the args of cond()
+    arg_name_ids = list(set(arg_name_ids) & set(parent_ids_dict))
+
+    arg_name_ids.sort()
     args = [
         gast.Name(
             id=name_id, ctx=gast.Load(), annotation=None, type_comment=None)
-        for name_id in name_ids
+        for name_id in arg_name_ids
     ]
     arguments = gast.arguments(
         args=args,
@@ -444,12 +472,14 @@ def transform_if_else(node, root):
     true_func_node = create_funcDef_node(
         node.body,
         name=unique_name.generate(TRUE_FUNC_PREFIX),
-        input_args=parse_cond_args(body_name_ids, modified_name_ids),
+        input_args=parse_cond_args(parent_name_ids, body_name_ids,
+                                   modified_name_ids),
         return_name_ids=return_name_ids)
     false_func_node = create_funcDef_node(
         node.orelse,
         name=unique_name.generate(FALSE_FUNC_PREFIX),
-        input_args=parse_cond_args(orelse_name_ids, modified_name_ids),
+        input_args=parse_cond_args(parent_name_ids, orelse_name_ids,
+                                   modified_name_ids),
         return_name_ids=return_name_ids)
     return create_new_vars_in_parent_stmts, true_func_node, false_func_node, return_name_ids
 

python/paddle/fluid/tests/unittests/dygraph_to_static/ifelse_simple_func.py

@@ -14,6 +14,7 @@
 
 from __future__ import print_function
 
+import paddle
 import paddle.fluid as fluid
 
 
@@ -99,6 +100,16 @@ def dyfunc_with_if_else3(x):
     return x
 
 
+def dyfunc_with_if_else_with_list_geneator(x):
+    if 10 > 5:
+        y = paddle.add_n(
+            [paddle.full(
+                shape=[2], fill_value=v) for v in range(5)])
+    else:
+        y = x
+    return y
+
+
 def nested_if_else(x_v):
     batch_size = 16
     feat_size = x_v.shape[-1]

python/paddle/fluid/tests/unittests/dygraph_to_static/test_ifelse.py

@@ -69,6 +69,12 @@ class TestDygraphIfElse3(TestDygraphIfElse):
         self.dyfunc = dyfunc_with_if_else3
 
 
+class TestDygraphIfElseWithListGenerator(TestDygraphIfElse):
+    def setUp(self):
+        self.x = np.random.random([10, 16]).astype('float32')
+        self.dyfunc = dyfunc_with_if_else_with_list_geneator
+
+
 class TestDygraphNestedIfElse(TestDygraphIfElse):
     def setUp(self):
         self.x = np.random.random([10, 16]).astype('float32')