585670 - Look into a smarter hash function for pointer and integer values

Status: NEW

(Core :: XPCOM, defect)

Description

[Zack Weinberg (:zwol)]

nsHashKeys.h has helper classes for hash tables indexed by pointers and integers (http://mxr.mozilla.org/mozilla-central/source/xpcom/glue/nsHashKeys.h#141 et seq).  These use an identity or near-identity hash function, which is suboptimal - we're likely to be hashing consecutive integers or closely-spaced pointer values.  It might be worth experimenting with the "integer hash functions" on these pages, to see if we get better collision behavior.

http://www.concentric.net/~Ttwang/tech/inthash.htm
http://burtleburtle.net/bob/hash/integer.html

(I don't know if we actually have any such hash tables that are perf-critical, though.)