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Re: [PATCH], Remove power9 fusion support
- From: Mike Stump <mikestump at comcast dot net>
- To: Michael Meissner <meissner at linux dot ibm dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Segher Boessenkool <segher at kernel dot crashing dot org>, David Edelsohn <dje dot gcc at gmail dot com>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Date: Mon, 5 Nov 2018 08:12:38 -0800
- Subject: Re: [PATCH], Remove power9 fusion support
- References: <20181102183734.GA27589@ibm-toto.the-meissners.org>
On Nov 2, 2018, at 11:37 AM, Michael Meissner <meissner@linux.ibm.com> wrote:
>
> As I discussed in my 2018 Cauldron talk, the PowerPC GCC compiler supported a
> subset of the original design for fusion in the power9 hardware using peepholes
> to fuse together ADDIS instructions and floating point load/store operations.
>
> However, while fusion was part of the original power9 design, by the time the
> machine came out, the fusion support was no longer part of the architecture.
>
> This patch removes all of the so-called power9 fusion support for the GCC
> compiler. It leaves -mpower9-fusion as a deprecated switch
So, I'd just remove the flag support as well. Anyone that hits on it, will want to examine their code and have the opportunity to fix it.