Amend last note.

1 files changed, 16 insertions, 0 deletions

diff --git a/notes/260929-color-bits.md b/notes/260929-color-bits.md
index 47dfcef..cd8b898 100644
--- a/notes/260929-color-bits.md
+++ b/notes/260929-color-bits.md
@@ -274,3 +274,19 @@ for coloring:
 
 * Black allocation sets the Grey and Black bits on freshly returned
   pointers, using the current values of the global mask variables.
+
+Oh, and by the way, having metadata bits on object pointers means you
+need to mask them off when comparing pointers:
+
+    equal(p1, p2) = (p1 & ~COLOR_BITS) == (p2 & ~COLOR_BITS)
+
+Probably not a big deal.
+
+Unpacking a NaN-packed pointer shouldn't need to do anything special;
+you just don't mind the GC bits.
+
+If we add static typing, it's more annoying, since we need to strip
+off bits on every dereference.  However, AArch64 has Top Byte Ignore.
+Intel and AMD are lagging far behind, but seem to have started adding
+similar features, like Intel LAM48/LAM57 and AMD UAI.  Hopefully, by
+the time Zisp is implemented, these will be universally available!