Hi Toni, On 6 November 2014 10:00, Armin Rigo <ar...@tunes.org> wrote: > gcc seems to perform this optimization for divide-by-constant where > the constant is exactly a finite power of two that is not a denormal. > These are the cases where the result is exactly the same. We could do > it too.
In short, what is needed is: - first check that the optimization you want to do is exact; trying it out on "gcc -O2 -S" without any "-ffast-math" flags is a good way to know. - if it is, then it's a matter of writing some simple code in rpython/jit/metainterp/optimizeopt/rewrite.py. Search for "float_mul" here; it will turn for example "f0 * -1.0" into a "float_neg" operation, with the comment that it is an exact optimization. - don't forget, start by adding a test to test/test_optimizebasic.py (search for "float_mul(-1.0, f0)" and add it nearby). You might find out that hacking the PyPy JIT at this level is rather easy :-) A bientôt, Armin. _______________________________________________ pypy-dev mailing list pypy-dev@python.org https://mail.python.org/mailman/listinfo/pypy-dev
