Re: [PATCH GCC][rework]Improve loop bound info by simplifying conversions in iv base

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

Ping.

On Thu, Aug 27, 2015 at 5:41 PM, Bin Cheng <bin.cheng@arm.com> wrote:
> Hi,
> This is a rework for
> https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02335.html, with review
> comments addressed.  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.  This kind of 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 moved from loop_exits_before_overflow.  After this
> patch, the corresponding code in loop_exits_before_overflow will be never
> executed, so I removed that part code.  The patch also includes some code
> format changes.
>
> Bootstrap and test on x86_64.  Is it OK?
>
> Thanks,
> bin
>
> 2015-08-27  Bin Cheng  <bin.cheng@arm.com>
>
>         * tree-ssa-loop-niter.c (tree_simplify_using_condition_1): Support
>         new parameter.
>         (tree_simplify_using_condition): Ditto.
>         (simplify_using_initial_conditions): Ditto.
>         (loop_exits_before_overflow): Pass new argument to function
>         simplify_using_initial_conditions.  Remove case for type conversions
>         simplification.
>         * tree-ssa-loop-niter.h (simplify_using_initial_conditions): New
>         parameter.
>         * tree-scalar-evolution.c (simple_iv): Simplify type conversions
>         in iv base using loop initial conditions.
>
> gcc/testsuite/ChangeLog
> 2015-08-27  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.