From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: Marcus Shawcroft <marcus.shawcroft@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
James Greenhalgh <james.greenhalgh@arm.com>
Subject: Re: [PATCH][AArch64] Use SUBS for parallel subtraction and comparison with immediate
Date: Fri, 02 Jun 2017 10:39:00 -0000 [thread overview]
Message-ID: <59314046.2060409@foss.arm.com> (raw)
In-Reply-To: <5914399D.9080606@foss.arm.com>
Ping.
Thanks,
Kyrill
On 11/05/17 11:14, Kyrill Tkachov wrote:
> Ping.
>
> https://gcc.gnu.org/ml/gcc-patches/2017-04/msg00932.html
>
> Thanks,
> Kyrill
>
> On 21/04/17 09:20, Kyrill Tkachov wrote:
>> Hi all,
>>
>> Our sub<mode>3_compare1 pattern is not enough to catch cases where we subtract an immediate
>> and compare against in PARALLEL. This is due to the RTL canonicalisation rules that require
>> subtractions of immediate IMM be represented as (plus x -IMM).
>> So we need a bit of trickery to catch those cases and this patch does that.
>> It adds a new define_insn to match the plus-negatable-immediate in parallel with a comparison
>> and a peephole that will bring the two together when possible.
>> Otherwise it's pretty straightforward.
>>
>> The testcase in the patch now generates a single SUBS-immediate instead of a SUB followed by a CMP.
>>
>> Bootstrapped and tested on aarch64-none-linux-gnu.
>>
>> Ok for GCC 8?
>>
>> Thanks,
>> Kyrill
>>
>> 2017-04-21 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
>>
>> * config/aarch64/aarch64.md (sub<mode>3_compare1_imm): New define_insn.
>> (peephole2): New peephole2 to emit the above.
>> * config/aarch64/predicates.md (aarch64_sub_immediate): New predicate.
>>
>> 2017-04-21 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
>>
>> * gcc.target/aarch64/subs_compare_2.c: New test.
>>
>
next prev parent reply other threads:[~2017-06-02 10:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-21 8:39 Kyrill Tkachov
2017-05-11 10:15 ` Kyrill Tkachov
2017-06-02 10:39 ` Kyrill Tkachov [this message]
2017-06-02 14:02 ` James Greenhalgh
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