Give meaning to the oparg for BUILD_MAP: estimated size of the dictionary.
Allows dictionaries to be pre-sized (upto 255 elements) saving time lost
to re-sizes with their attendant mallocs and re-insertions.
Has zero effect on small dictionaries (5 elements or fewer), a slight
benefit for dicts upto 22 elements (because they had to resize once
anyway), and more benefit for dicts upto 255 elements (saving multiple
resizes during the build-up and reducing the number of collisions on
the first insertions). Beyond 255 elements, there is no addional benefit.
diff --git a/Misc/NEWS b/Misc/NEWS
index 1599ade..40e9e6a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,10 @@
Core and builtins
-----------------
+- Compiler now generates simpler and faster code for dictionary literals.
+ The oparg for BUILD_MAP now indicates an estimated dictionary size.
+ There is a new opcode, STORE_MAP, for adding entries to the dictionary.
+
- Issue #1638: %zd configure test fails on Linux
- Issue #1620: New property decorator syntax was modifying the decorator