[PATCH PR70715]Expand simple operations in IV.base and check if it's the control_IV

[Christophe Lyon]

On 22 April 2016 at 17:38, Bin.Cheng <amker.cheng@gmail.com> wrote:
> On Fri, Apr 22, 2016 at 4:26 PM, Christophe Lyon
> <christophe.lyon@linaro.org> wrote:
>> On 21 April 2016 at 11:03, Richard Biener <richard.guenther@gmail.com> wrote:
>>> On Wed, Apr 20, 2016 at 5:08 PM, Bin Cheng <Bin.Cheng@arm.com> wrote:
>>>> Hi,
>>>> As reported in PR70715, GCC failed to prove no-overflows of IV(&p[n]) for simple example like:
>>>> int
>>>> foo (char *p, unsigned n)
>>>> {
>>>>   while(n--)
>>>>     {
>>>>       p[n]='A';
>>>>     }
>>>>   return 0;
>>>> }
>>>> Actually, code has already been added to handle this form loops when fixing PR68529.  Problem with this case is loop niter analyzer records control_IV with its base expanded by calling expand_simple_operations.  This patch simply adds code expanding BASE before we check its equality against control_IV.base.  In the long run, we might want to remove the use of expand_simple_operations.
>>>>
>>>> Bootstrap and test on x86_64.  Is it OK?
>>>
>>
>> Hi Bin,
>>
>> On ARM and AArch64 bare-metal toolchains, this causes
>>
>> FAIL: gcc.dg/tree-ssa/minmax-2.c scan-tree-dump optimized "__builtin_fmin"
> Hi Christophe,
> As Kyrill pointed out, it doesn't look likely.  The case doesn't even
> have a loop for the patch to apply?
>

Ha, you are right, sorry for the noise.

I've had a lot of infrastructure problems these days with many build
failures, introducing noise in the results :(

Christophe

> Thanks,
> bin
>>
>> Christophe
>>
>>> Ok.
>>>
>>> Richard.
>>>
>>>> Thanks,
>>>> bin
>>>>
>>>>
>>>> 2016-04-20  Bin Cheng  <bin.cheng@arm.com>
>>>>
>>>>         PR tree-optimization/70715
>>>>         * tree-ssa-loop-niter.c (loop_exits_before_overflow): Check equality
>>>>         after expanding BASE using expand_simple_operations.