Re: [PATCH][simplify-rtx] (GTU (PLUS a C) (C - 1)) --> (LTU a -C)

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

On 16/09/16 11:45, Bernd Schmidt wrote:
> On 09/16/2016 10:40 AM, Kyrill Tkachov wrote:
>>
>> 2016-09-16  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>     * simplify-rtx.c (simplify_relational_operation_1): Add transformation
>>     (GTU (PLUS a C) (C - 1)) --> (LTU a -C).
>>
>> 2016-09-16  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>     * gcc.target/aarch64/gtu_to_ltu_cmp_1.c: New test.
>
> Ok. Don't know if you want to add more variants of the input code to the testcase to make sure they're all covered.
>

Thanks.
I'm having trouble writing testcases for variations of the original testcase as GCC really really wants to convert
everything to a comparison against 1 at RTL level, so only the x == -2 || x == -1 condition seems to trigger this.
However, testcases of the form:
unsigned int
foo (unsigned int a, unsigned int b)
{
   return (a + 10) > 9;
}

seem to trigger it, so I can add some of this form. However, these will be optimised by a match.pd version
of this transformation that I'm working on.

Kyrill

>
> Bernd