Here is a slight respin.
The important parts are the same, just the expander now uses the slightly shorter
arm_gen_compare_reg and the rtx costs hunk is moved under an explicit case MOD.

Note, the tests still require patch 1/3 that does this for aarch64 that I hope to post
a respinned version of soon.

Ok after the prerequisite goes in?

Thanks,
Kyrill


2015-08-10  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * config/arm/arm.md (*subsi3_compare0): Rename to...
     (subsi3_compare0): ... This.
     (*arm_andsi3_insn): Rename to...
     (arm_andsi3_insn): ... This.
     (modsi3): New define_expand.
     * config/arm/arm.c (arm_new_rtx_costs, MOD case): Handle case
     when operand is power of 2.


2015-08-10  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * gcc.target/aarch64/mod_2.x: New file.
     * gcc.target/aarch64/mod_256.x: Likewise.
     * gcc.target/arm/mod_2.c: New test.
     * gcc.target/arm/mod_256.c: Likewise.
     * gcc.target/aarch64/mod_2.c: Likewise.
     * gcc.target/aarch64/mod_256.c: Likewise.



On 31/07/15 09:20, Kyrill Tkachov wrote:
> Ping.
>
> https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02037.html
> Thanks,
> Kyrill
>
> On 24/07/15 11:55, Kyrill Tkachov wrote:
>> Hi all,
>>
>> This third patch implements the same algorithm as patch 1/3 but for arm.
>> That is, for X % N where N is a power of 2 we do:
>>
>>     rsbs    r1, r0, #0
>>     and     r0, r0, #(N - 1)
>>     and     r1, r1, #(N - 1)
>>     rsbpl   r0, r1, #0
>>
>> For the special case where N is 2 we do the shorter:
>>      cmp     r0, #0
>>      and     r0, r0, #1
>>      rsblt   r0, r0, #0
>>
>> Note that for the final conditional negate we expand to an IF_THEN_ELSE of a NEG
>> rather than a cond_exec rtx because the lra dataflow analysis doesn't always deal
>> with cond_execs correctly. The splitters fixed in patch 2/3 then break it into a
>> cond_exec after reload, so it all works out.
>>
>> Bootstrapped and tested on arm, with both ARM and Thumb2 states.
>>
>> Tests are added and shared with aarch64.
>>
>> Ok for trunk?
>>
>> Thanks,
>> Kyrill
>>
>> 2015-07-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>        * config/arm/arm.md (*subsi3_compare0): Rename to...
>>        (subsi3_compare0): ... This.
>>        (*arm_andsi3_insn): Rename to...
>>        (arm_andsi3_insn): ... This.
>>        (modsi3): New define_expand.
>>        * config/arm/arm.c (arm_new_rtx_costs, MOD case): Handle case
>>        operand is power of 2.
>>
>>
>> 2015-07-24  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
>>
>>        * gcc.target/aarch64/mod_2.x: New file.
>>        * gcc.target/aarch64/mod_256.x: Likewise.
>>        * gcc.target/arm/mod_2.c: New test.
>>        * gcc.target/arm/mod_256.c: Likewise.
>>        * gcc.target/aarch64/mod_2.c: Likewise.
>>        * gcc.target/aarch64/mod_256.c: Likewise.