From: Bill Schmidt <wschmidt@linux.ibm.com>
To: Michael Meissner <meissner@linux.ibm.com>,
gcc-patches@gcc.gnu.org,
Segher Boessenkool <segher@kernel.crashing.org>,
David Edelsohn <dje.gcc@gmail.com>,
Peter Bergner <bergner@linux.ibm.com>,
Will Schmidt <will_schmidt@vnet.ibm.com>,
HAO CHEN GUI <guihaoc@linux.ibm.com>
Subject: Re: [PATCH 0/3] Add zero cycle move support
Date: Mon, 22 Nov 2021 09:57:57 -0600 [thread overview]
Message-ID: <3a44458a-6682-0bde-0560-fcec5455c386@linux.ibm.com> (raw)
In-Reply-To: <YZe5llec+qA6YdtE@toto.the-meissners.org>
Hi!
On 11/19/21 8:49 AM, Michael Meissner wrote:
> The next set of 3 patches add zero cycle move support to the Power10. Zero
> cycle moves are where the move to LR/CTR/TAR register that is adjacent to the
> jump to LR/CTR/TAR register can be fused together.
>
> At the moment, these set of three patches add support for zero cycle moves for
> indirect jumps and switch tables using the CTR register. Potential zero cycle
> moves for doing returns are not currently handled.
>
> In looking at the code, I discovered that just using zero cycle moves isn't as
> helpful unless we can eliminate the add instruction before doing the jump. I
> also noticed that the various power10 fusion options are only done if
> -mcpu=power10. I added a patch to do the fusion for -mtune=power10 as well.
>
> I have done bootstraps and make check with these patches installed on both
> little endian power9 and little endian power10 systems. Can I install these
> patches?
>
> The following patches will be posted:
>
> 1) Patch to add zero cycle move for indirect jumps and switches.
>
> 2) Patch to enable p10 fusion for -mtune=power10 in addition to -mcpu=power10.
>
> 3) Patch to use absolute addresses for switch tables instead of relative
> addresses if zero cycle fusion is enabled.
>
For this last point, I had thought that the plan was to always switch over to
absolute addresses for switch tables, following the work that Hao Chen did in
this area. Am I misremembering? Hao Chen, can you please remind me where we
ended up here?
Thanks!
Bill
next prev parent reply other threads:[~2021-11-22 15:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-19 14:49 Michael Meissner
2021-11-19 14:53 ` [PATCH 1/3] Add power10 zero cycle moves for switches & indirect jumps Michael Meissner
2021-11-22 16:36 ` Bill Schmidt
2021-11-22 21:12 ` Michael Meissner
2021-12-13 17:10 ` Ping: " Michael Meissner
2021-11-19 14:55 ` [PATCH 2/3] Set power10 fusion if -mtune=power10 Michael Meissner
2021-11-22 16:06 ` Bill Schmidt
2021-11-22 21:13 ` Michael Meissner
2021-12-13 17:12 ` Ping: " Michael Meissner
2021-11-19 14:57 ` [PATCH 3/3] Use absolute switch table addresses for zero cycle moves Michael Meissner
2021-12-13 17:13 ` Ping: " Michael Meissner
2021-11-22 15:57 ` Bill Schmidt [this message]
2021-11-22 16:09 ` [PATCH 0/3] Add zero cycle move support David Edelsohn
2021-11-22 21:17 ` Michael Meissner
2021-11-23 3:41 ` HAO CHEN GUI
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