From: Andrew Pinski <pinskia@gmail.com>
To: Jim Wilson <jim.wilson@linaro.org>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
Jim Wilson <wilson@tuliptree.org>
Subject: Re: [PATCH, AArch64] Disable reg offset in quad-word store for Falkor.
Date: Fri, 22 Sep 2017 17:59:00 -0000 [thread overview]
Message-ID: <CA+=Sn1=Noh74J+Y0j40GRxT9ZBCr+6UeTr3biftfdgaG96hXmg@mail.gmail.com> (raw)
In-Reply-To: <CABXYE2WyDADSL_eDPKDKMj8iJcRQt9K-TbpXc7rVdKeVHp1rrg@mail.gmail.com>
On Fri, Sep 22, 2017 at 8:59 AM, Jim Wilson <jim.wilson@linaro.org> wrote:
> On Fri, Sep 22, 2017 at 8:49 AM, Jim Wilson <jim.wilson@linaro.org> wrote:
>> On Falkor, because of an idiosyncracy of how the pipelines are designed, a
>> quad-word store using a reg+reg addressing mode is almost twice as slow as an
>> add followed by a quad-word store with a single reg addressing mode. So we
>> get better performance if we disallow addressing modes using register offsets
>> with quad-word stores.
>
> This was tested with a bootstrap and make check of course. Also,
> gcc.c-torture/compile/20021212-1.c compiled with -O3 -mcpu=falkor
> makes a nice testcase to demonstrate that the patch works.
>
> OK?
Two overall comments:
* What about splitting register_offset into two different elements,
one for non 128bit modes and one for 128bit (and more; OI, etc.) modes
so you get better address generation right away for the simd load
cases rather than having LRA/reload having to reload the address into
a register.
* Maybe adding a testcase to the testsuite to show this change.
One extra comment:
* should we change the generic tuning to avoid reg+reg for 128bit modes?
Thanks,
Andrew
>
> Jim
next prev parent reply other threads:[~2017-09-22 17:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-22 15:49 Jim Wilson
2017-09-22 15:59 ` Jim Wilson
2017-09-22 17:59 ` Andrew Pinski [this message]
2017-09-22 18:39 ` Jim Wilson
2017-09-22 21:11 ` Andrew Pinski
2017-10-12 21:54 ` Jim Wilson
2017-10-31 3:40 ` Kugan Vivekanandarajah
2017-10-31 16:18 ` Jim Wilson
2017-11-01 22:59 ` Kugan Vivekanandarajah
2017-09-22 20:06 Wilco Dijkstra
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