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Re: [PATCH, i386]: Do not limit the cost of moves to/from XMM register to minimum 8.
- From: Hongtao Liu <crazylht at gmail dot com>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Date: Fri, 30 Aug 2019 08:10:26 +0800
- Subject: Re: [PATCH, i386]: Do not limit the cost of moves to/from XMM register to minimum 8.
- References: <CAFULd4ZOgSxG5sn2Y7Rbpn8mcykO29mV_LenpKK+KuAte-0m_g@mail.gmail.com>
On Fri, Aug 30, 2019 at 2:09 AM Uros Bizjak <ubizjak@gmail.com> wrote:
>
> 2019-08-28 Uroš Bizjak <ubizjak@gmail.com>
>
> * config/i386/i386.c (ix86_register_move_cost): Do not
> limit the cost of moves to/from XMM register to minimum 8.
>
> Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
>
> Actually committed as r274994 with the wrong ChangeLog.
>
> Uros.
There is 11% regression in 548.exchange_r of SPEC2017.
Reason for the regression:
For 548.exchange_r, a lot of movements between gpr and xmm are
generated as expected,
and it reduced clocksticks by 3%.
But however maybe too many xmm registers are used,
a frequency reduction issue is triggered(average frequency reduced by 13%).
So totally it takes more time.
--
BR,
Hongtao