Re: [PATCH] Factor out division by squares and remove division around comparisons (1/2)

[Jackson Woodruff <jackson dot woodruff at foss dot arm dot com>]

And have now attached that patch.

Jackson


On 08/10/2017 03:09 PM, Jackson Woodruff wrote:
> Hi all,
>
> The patch implements the division opitmizations discussed in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026 .
>
> The implemented change differs slightly from the
> proposed one in that we re-associate:
>
>     C / x comparison 0.0 -> x comparison' 0.0
>
> Where C is any constant and comparison' is changed as
> appropriate if C is negative.
>
> The implementations also removes the division from:
>
>     x / C comparison 0.0 -> x comparison' 0.0
>
> Where again, comparison' is changed as appropriate if C is
> negative.
>
> We also change the association of
>
>      x / (y * C) -> (x / C) / y
>
> If C is a constant. All of the above require
> -funsafe-math-optimizations.
>
> We also change:
>
>   x / (- y) -> (-x) / y
>
> Which requires -fno-trapping-math.
>
> Bootstrapped and regtested (with part 2 of this patch) on aarch64.
>
> OK for trunk?
>
> (Apologies if the recipients in the 'to' field received this twice,
> I accidentally sent this from an email gcc-patches doesn't accept)
>
> Jackson
>
> gcc/
>
> 2017-08-03  Jackson Woodruff  <jackson.woodruff@arm.com>
>
>     PR 71026/tree-optimization
>     * match.pd: New patterns.
>
>
> gcc/testsuite
>
> 2017-08-03  Jackson Woodruff  <jackson.woodruff@arm.com>
>
>     PR 71026/tree-optimization
>     * gcc.dg/associate_comparison_1.c: New.
>     * gcc.dg/associate_division_2.c: New.

Attachment: patchfile-1
Description: Text document