On Tue, Apr 19, 2016 at 1:35 PM, Richard Biener <richard.guent...@gmail.com> wrote: > On Mon, Feb 29, 2016 at 11:53 AM, kugan > <kugan.vivekanandara...@linaro.org> wrote: >>> >>> Err. I think the way you implement that in reassoc is ad-hoc and not >>> related to reassoc at all. >>> >>> In fact what reassoc is missing is to handle >>> >>> -y * z * (-w) * x -> y * x * w * x >>> >>> thus optimize negates as if they were additional * -1 entries in a >>> multiplication chain. And >>> then optimize a single remaining * -1 in the result chain to a negate. >>> >>> Then match.pd handles x + (-y) -> x - y (independent of -frounding-math >>> btw). >>> >>> So no, this isn't ok as-is, IMHO you want to expand the multiplication ops >>> chain >>> pulling in the * -1 ops (if single-use, of course). >>> >> >> I agree. Here is the updated patch along what you suggested. Does this look >> better ? > > It looks better but I think you want to do factor_out_negate_expr before the > first qsort/optimize_ops_list call to catch -1. * z * (-w) which also means > you > want to simply append a -1. to the ops list rather than adjusting the result > with a negate stmt. > > You also need to guard all this with ! HONOR_SNANS (type) && (! > HONOR_SIGNED_ZEROS (type) > || ! COMPLEX_FLOAT_TYPE_P (type)) (see match.pd pattern transforming x > * -1. to -x).
And please add at least one testcase. Richard. > Richard. > >> Thanks, >> Kugan
