[pypy-commit] pypy default: Expand a bit more the comment

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r54552:d9b5f8a7d8fe
Date: 2012-04-19 19:46 +0200
http://bitbucket.org/pypy/pypy/changeset/d9b5f8a7d8fe/

Log:	Expand a bit more the comment

diff --git a/pypy/jit/backend/x86/assembler.py b/pypy/jit/backend/x86/assembler.py
--- a/pypy/jit/backend/x86/assembler.py
+++ b/pypy/jit/backend/x86/assembler.py
@@ -1656,8 +1656,11 @@
         else:
             # XXX hard-coded assumption: to go from an object to its class
             # we use the following algorithm:
-            #   - read the typeid from mem(locs[0]), i.e. at offset 0
-            #   - keep the lower half-word read there
+            #   - read the typeid from mem(locs[0]), i.e. at offset 0;
+            #     this is a complete word (N=4 bytes on 32-bit, N=8 on
+            #     64-bits)
+            #   - keep the lower half of what is read there (i.e.
+            #     truncate to an unsigned 'N / 2' bytes value)
             #   - multiply by 4 (on 32-bits only) and use it as an
             #     offset in type_info_group
             #   - add 16/32 bytes, to go past the TYPE_INFO structure