Bad hpc hash function

[Lennart]

In the hpc module Trace.Hpc.Util there is the following code:

instance (HpcHash a,HpcHash b) => HpcHash (a,b) where
  toHash (a,b) = toHash a * 33 `hxor` toHash b

This is bad and I can only presume that what was actually intended was

instance (HpcHash a,HpcHash b) => HpcHash (a,b) where
  toHash (a,b) = (toHash a * 33) `hxor` toHash b

Otherwise a hash of 0 for a will result in a total hash of 0.

[simonmar]

Ok, I'll push the fix. Thanks.

[simonmar]

commit 4d661848575009bbcf3fe8e1f7c69da12f1d3a8e
Author: Simon Marlow <marlowsd@gmail.com>
Date:   Tue Mar 20 12:12:06 2012 +0000

    fix bug in instance HpcHash (a,b) (GHC ticket #5944)

[pcapriotti]

Merged as ffd12b9a17dfdffef8ca4dd215e5c081d9b082fa.