[issue22501] Optimise PyLong division by 1 or -1

[Stefan Behnel]

New submission from Stefan Behnel:

The attached patch adds fast paths for PyLong division by 1 and -1, as well as dividing 0 by something. This was found helpful for fractions normalisation, as the GCD that is divided by can often be |1|, but firing up the whole division machinery for this eats a lot of CPU cycles for nothing.

There are currently two test failures in test_long.py because dividing a huge number by 1 or -1 no longer raises an OverflowError. This is a behavioural change, but I find it acceptable. If others agree, I'll fix the tests and submit a new patch.

----------
components: Interpreter Core
files: div_by_1_fast_path.patch
keywords: patch
messages: 227590
nosy: mark.dickinson, pitrou, scoder, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Optimise PyLong division by 1 or -1
type: performance
versions: Python 3.5
Added file: http://bugs.python.org/file36729/div_by_1_fast_path.patch

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue22501>
_______________________________________