RE: [EXT] Re: [dpdk-dev] [PATCH v2] eal/arm: remove CASP constraints for GCC

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>On Mon, Nov 8, 2021 at 8:15 AM Ruifeng Wang
><Ruifeng.Wang@arm.com> wrote:
>>
>> > -----Original Message-----
>> > From: pbhagavatula@marvell.com <pbhagavatula@marvell.com>
>> > Sent: Friday, November 5, 2021 4:57 PM
>> > To: Ruifeng Wang <Ruifeng.Wang@arm.com>;
>david.marchand@redhat.com;
>> > jerinj@marvell.com
>> > Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@marvell.com>
>> > Subject: [dpdk-dev] [PATCH v2] eal/arm: remove CASP constraints
>for GCC
>> >
>> > From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> >
>> > GCC now assigns even register pairs for CASP, the fix has also been
>> > backported to all stable releases of older GCC versions.
>> > Removing the manual register allocation allows GCC to inline the
>functions
>> > and pick optimal registers for performing CASP.
>> >
>> > Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> Acked-by: Ruifeng Wang <ruifeng.wang@arm.com>
>
>Patch lgtm but it is late for merging in 21.11.
>
>It is in EAL, and is an optimisation of the 128 bits cas operation on ARM.
>This is used by the stack library and mempool.
>There might be other impacts I did not think of.
>
>
>Do you have links to bugs or commits for the mentionned fix on gcc
>side?

Here is the gcc git commit that fixes this.

https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=563cc649beaf11d707c422e5f4e9e5cdacb818c3

>This will help when we get reports from users with compilers without
>the fix.
>
>
>Thanks.
>
>--
>David Marchand