From: Segher Boessenkool <segher@kernel.crashing.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH v1 4/5] powerpc/44x: Fix build failure with GCC 12 (unrecognized opcode: `wrteei')
Date: Mon, 11 Jul 2022 12:12:26 -0500 [thread overview]
Message-ID: <20220711171226.GG25951@gate.crashing.org> (raw)
In-Reply-To: <CAK8P3a33jf5CUpyzWmRHpoUDMWB7TqSw5afUW=rcmMVSK8BvRA@mail.gmail.com>
On Mon, Jul 11, 2022 at 05:05:04PM +0200, Arnd Bergmann wrote:
> Is there any value in building for -mcpu=440 or -mcpu=464 when targeting a 476?
The original 440 had a very short pipeline. Later IBM 4xx have a longer
pipeline. Getting this right (with -mtune=, or just with -mcpu=) is
important for performance. So, no?
> Maybe add another !PPC_47x dependency for the first two. Ideally we would also
> enforce that 440/464 based boards cannot be selected together with 476, though
> I guess that is a separate issue.
>
> Is there a practical difference between 440 and 464 when building kernels?
> gcc seems to treat them the same way, so maybe one option for both is enough
> here.
-mcpu= is used as the default for -mtune=, so that is always a
consideration. PPC464 is treated the same as PPC440 in binutils as
well, so I don't think there is any issue there.
Segher
next prev parent reply other threads:[~2022-07-11 17:15 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-11 14:19 [PATCH v1 1/5] powerpc/32: Do not allow selection of e5500 or e6500 CPUs on PPC32 Christophe Leroy
2022-07-11 14:19 ` [PATCH v1 2/5] powerpc/32: Don't always pass -mcpu=powerpc to the compiler Christophe Leroy
2022-07-11 16:50 ` Segher Boessenkool
2022-08-18 17:46 ` Pali Rohár
2022-08-20 10:55 ` Pali Rohár
2022-07-11 14:19 ` [PATCH v1 3/5] powerpc/405: Fix build failure with GCC 12 (unrecognized opcode: `wrteei') Christophe Leroy
2022-07-11 14:19 ` [PATCH v1 4/5] powerpc/44x: " Christophe Leroy
2022-07-11 15:05 ` Arnd Bergmann
2022-07-11 15:49 ` Christophe Leroy
2022-07-11 17:12 ` Segher Boessenkool [this message]
2022-07-11 14:19 ` [PATCH v1 5/5] powerpc/64e: " Christophe Leroy
2022-12-11 17:32 ` Pali Rohár
2022-12-12 7:36 ` Christophe Leroy
2022-12-12 10:27 ` Michael Ellerman
2022-07-11 16:39 ` [PATCH v1 1/5] powerpc/32: Do not allow selection of e5500 or e6500 CPUs on PPC32 Segher Boessenkool
2022-07-11 17:42 ` Christophe Leroy
2022-07-29 13:02 ` Michael Ellerman
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