Re: [PATCH GCC]Improve bound information in loop niter analysis

["Bin.Cheng" <amker.cheng@gmail.com>]

Ping.

Thanks,
bin

On Tue, Jul 28, 2015 at 5:36 PM, Bin Cheng <bin.cheng@arm.com> wrote:
> Hi,
> Loop niter computes inaccurate bound information for different loops.  This
> patch is to improve it by using loop initial condition in
> determine_value_range.  Generally, loop niter is computed by subtracting
> start var from end var in loop exit condition.  Moreover, loop bound is
> computed using value range information of both start and end variables.
> Basic idea of this patch is to check if loop initial condition implies more
> range information for both start/end variables.  If yes, we refine range
> information and use that to compute loop bound.
> With this improvement, more accurate loop bound information is computed for
> test cases added by this patch.
>
> Is it OK?
>
> Thanks,
> bin
>
> 2015-07-28  Bin Cheng  <bin.cheng@arm.com>
>
>         * tree-ssa-loop-niter.c (refine_value_range_using_guard): New.
>         (determine_value_range): Call refine_value_range_using_guard for
>         each loop initial condition to improve value range.
>
> gcc/testsuite/ChangeLog
> 2015-07-28  Bin Cheng  <bin.cheng@arm.com>
>
>         * gcc.dg/tree-ssa/loop-bound-1.c: New test.
>         * gcc.dg/tree-ssa/loop-bound-3.c: New test.
>         * gcc.dg/tree-ssa/loop-bound-5.c: New test.