[pypy-commit] pypy speedup-list-comprehension: redo the reasonable part

[fijal]

Author: Maciej Fijalkowski <fijall at gmail.com>
Branch: speedup-list-comprehension
Changeset: r52828:45a68e50a262
Date: 2012-02-23 19:34 -0700
http://bitbucket.org/pypy/pypy/changeset/45a68e50a262/

Log:	redo the reasonable part

diff --git a/pypy/interpreter/astcompiler/codegen.py b/pypy/interpreter/astcompiler/codegen.py
--- a/pypy/interpreter/astcompiler/codegen.py
+++ b/pypy/interpreter/astcompiler/codegen.py
@@ -965,7 +965,7 @@
         self.emit_op_arg(ops.CALL_METHOD, (kwarg_count << 8) | arg_count)
         return True
 
-    def _listcomp_generator(self, gens, gen_index, elt, outermost=False):
+    def _listcomp_generator(self, gens, gen_index, elt, single=False):
         start = self.new_block()
         skip = self.new_block()
         if_cleanup = self.new_block()
@@ -973,8 +973,8 @@
         gen = gens[gen_index]
         assert isinstance(gen, ast.comprehension)
         gen.iter.walkabout(self)
-        if outermost:
-            self.emit_op(ops.BUILD_LIST_FROM_ARG)
+        if single:
+            self.emit_op_arg(ops.BUILD_LIST_FROM_ARG, 0)
         self.emit_op(ops.GET_ITER)
         self.use_next_block(start)
         self.emit_jump(ops.FOR_ITER, anchor)
@@ -1000,7 +1000,12 @@
 
     def visit_ListComp(self, lc):
         self.update_position(lc.lineno)
-        self._listcomp_generator(lc.generators, 0, lc.elt, outermost=True)
+        if len(lc.generators) != 1 or lc.generators[0].ifs:
+            single = False
+            self.emit_op_arg(ops.BUILD_LIST, 0)
+        else:
+            single = True
+        self._listcomp_generator(lc.generators, 0, lc.elt, single=single)
 
     def _comp_generator(self, node, generators, gen_index):
         start = self.new_block()