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Date: Thu, 13 Aug 2015 08:58:00 -0000
Message-ID: <CAHFci2-WeuRfCUtD79Quj7g8qkGLwQiW3q--5wkD+7Bvv2mBnw@mail.gmail.com>
Subject: Re: [PATCH GCC]Improve loop bound info by simplifying conversions in iv base
From: "Bin.Cheng" <amker.cheng@gmail.com>
To: Bin Cheng <bin.cheng@arm.com>
Cc: gcc-patches List <gcc-patches@gcc.gnu.org>
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Ping.

Thanks,
bin

On Tue, Jul 28, 2015 at 5:38 PM, Bin Cheng <bin.cheng@arm.com> wrote:
> Hi,
> For now, SCEV may compute iv base in the form of "(signed T)((unsigned
> T)base + step))".  This complicates other optimizations/analysis depending
> on SCEV because it's hard to dive into type conversions.  For many cases,
> such type conversions can be simplified with additional range information
> implied by loop initial conditions.  This patch does such simplification.
> With simplified iv base, loop niter analysis can compute more accurate bound
> information since sensible value range can be derived for "base+step".  For
> example, accurate loop bound&may_be_zero information is computed for cases
> added by this patch.
> The code is actually borrowed from loop_exits_before_overflow.  Moreover,
> with simplified iv base, the second case handled in that function now
> becomes the first case.  I didn't remove that part of code because it may(?)
> still be visited in scev analysis itself and simple_iv isn't an interface
> for that.
>
> Is it OK?
>
> Thanks,
> bin
>
> 2015-07-28  Bin Cheng  <bin.cheng@arm.com>
>
>         * tree-ssa-loop-niter.c (tree_simplify_using_condition): Export
>         the interface.
>         * tree-ssa-loop-niter.h (tree_simplify_using_condition): Declare.
>         * tree-scalar-evolution.c (simple_iv): Simplify type conversions
>         in iv base using loop initial conditions.
>
> gcc/testsuite/ChangeLog
> 2015-07-28  Bin Cheng  <bin.cheng@arm.com>
>
>         * gcc.dg/tree-ssa/loop-bound-2.c: New test.
>         * gcc.dg/tree-ssa/loop-bound-4.c: New test.
>         * gcc.dg/tree-ssa/loop-bound-6.c: New test.