[pypy-commit] pypy default: When a key in a celldict is set with it's current value, don't create a level of indirection, or mutate the version. This shows up for the attributes of all MixedModules (including __builtins__!).

[alex_gaynor]

Author: Alex Gaynor <alex.gaynor at gmail.com>
Branch: 
Changeset: r47019:a9ad422cdb38
Date: 2011-09-02 08:54 -0400
http://bitbucket.org/pypy/pypy/changeset/a9ad422cdb38/

Log:	When a key in a celldict is set with it's current value, don't
	create a level of indirection, or mutate the version. This shows up
	for the attributes of all MixedModules (including __builtins__!).

diff --git a/pypy/module/pypyjit/test_pypy_c/test_globals.py b/pypy/module/pypyjit/test_pypy_c/test_globals.py
--- a/pypy/module/pypyjit/test_pypy_c/test_globals.py
+++ b/pypy/module/pypyjit/test_pypy_c/test_globals.py
@@ -23,6 +23,4 @@
             guard_not_invalidated(descr=...)
             p19 = getfield_gc(ConstPtr(p17), descr=<GcPtrFieldDescr .*W_DictMultiObject.inst_strategy .*>)
             guard_value(p19, ConstPtr(ptr20), descr=...)
-            p22 = getfield_gc(ConstPtr(ptr21), descr=<GcPtrFieldDescr .*ModuleCell.inst_w_value .*>)
-            guard_nonnull(p22, descr=...)
-        """)
+        """)
\ No newline at end of file
diff --git a/pypy/objspace/std/celldict.py b/pypy/objspace/std/celldict.py
--- a/pypy/objspace/std/celldict.py
+++ b/pypy/objspace/std/celldict.py
@@ -65,6 +65,10 @@
         if isinstance(cell, ModuleCell):
             cell.w_value = w_value
             return
+        # If the new value and the current value are the same, don't create a
+        # level of indirection, or mutate are version.
+        if self.space.is_w(w_value, cell):
+            return
         if cell is not None:
             w_value = ModuleCell(w_value)
         self.mutated()
diff --git a/pypy/objspace/std/test/test_celldict.py b/pypy/objspace/std/test/test_celldict.py
--- a/pypy/objspace/std/test/test_celldict.py
+++ b/pypy/objspace/std/test/test_celldict.py
@@ -39,6 +39,20 @@
         assert d.getitem("a") is None
         assert d.strategy.getdictvalue_no_unwrapping(d, "a") is None
 
+    def test_same_key_set_twice(self):
+        strategy = ModuleDictStrategy(space)
+        storage = strategy.get_empty_storage()
+        d = W_DictMultiObject(space, strategy, storage)
+
+        v1 = strategy.version
+        x = object()
+        d.setitem("a", x)
+        v2 = strategy.version
+        assert v1 is not v2
+        d.setitem("a", x)
+        v3 = strategy.version
+        assert v2 is v3
+
 class AppTestModuleDict(object):
     def setup_class(cls):
         cls.space = gettestobjspace(**{"objspace.std.withcelldict": True})