Re: Fold some equal to and not equal to patterns in match.pd

[Kyrill Tkachov <kyrylo.tkachov@arm.com>]

On 21/07/15 10:26, pinskia@gmail.com wrote:
>
>
>
>> On Jul 21, 2015, at 2:15 AM, Hurugalawadi, Naveen <Naveen.Hurugalawadi@caviumnetworks.com> wrote:
>>
>> Hi,
>>
>> Please find attached the patch which performs following patterns folding
>> in match.pd:-
>>
>> a ==/!= a p+ b to b ==/!= 0.
>> a << N ==/!= 0 to a&(-1>>N) ==/!= 0.
>> a * N ==/!= 0 where N is a power of 2 to a & (-1<<N2) ==/!= 0 where N2 is log2 of N.
>>
>> Please review the same and let us know if its okay?
> I should note this shows up in perlbmk in spec 2006.

Yes, I see it triggering there for aarch64, but I also see some undesired effects,
for example in gcc:
     lsl    x24, x24, 3
     cbz    x24, .L1194

now becomes:
     and    x0, x24, 2305843009213693951
     lsl    x24, x24, 3
     cbz    x0, .L1194

> Thanks,
> Andrew
>
>> Regression Tested on X86_64.
>>
>> On Behalf of Andrew Pinski.
>>
>> Thanks,
>>
>> gcc/testsuite/ChangeLog:
>>
>> 2015-01-21  Andrew Pinski  <apinski@cavium.com>
>>
>>     * testsuite/gcc.dg/tree-ssa/compare-shiftmult-1.c: New testcase.
>>     * testsuite/gcc.dg/tree-ssa/compare_pointers-1.c: New testcase.
>>
>> gcc/ChangeLog:
>>
>> 2015-01-21  Andrew Pinski  <apinski@cavium.com>
>>
>>     * match.pd (define_predicates): Add integer_pow2p.
>>     Add pattern for folding of a ==/!= a p+ b to b ==/!= 0.
>>     (unsigned_integral_valued_p): New match.
>>     Add pattern for folding of a<<N ==/!= 0 to a&(-1>>N) ==/!= 0.
>>     Add pattern for folding of a*N ==/!= 0 where N is a power of 2
>>     to a&(-1<<N2) ==/!= 0 where N2 is log2 of N.
>> <gcc_match.patch>