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Re: [PATCH], Enable -mfloat128 by default on PowerPC VSX systems
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Michael Meissner <meissner at linux dot vnet dot ibm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, David Edelsohn <dje dot gcc at gmail dot com>, Bill Schmidt <wschmidt at linux dot vnet dot ibm dot com>
- Date: Fri, 18 Aug 2017 15:57:30 -0500
- Subject: Re: [PATCH], Enable -mfloat128 by default on PowerPC VSX systems
- Authentication-results: sourceware.org; auth=none
- References: <20170816225950.GA2292@ibm-tiger.the-meissners.org>
On Wed, Aug 16, 2017 at 06:59:50PM -0400, Michael Meissner wrote:
> This patch enables -mfloat128 to be the default on PowerPC Linux VSX systems.
>
> This patch depends on the libquadmatch/81848 patch being approved and
> installed:
> https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00977.html
That patch is still waiting, but I'll review this one already.
> I've checked this on a big endian power7 system (both 32-bit and 64-bit) and a
> little endian power8 system.
It may be good to test it on a system without VSX as well, if you can?
> +The default for @option{-mfloat128} is enabled on PowerPC Linux
> +systems using the VSX instruction set, and disabled on other systems.
> +
> +The VSX instruction set (@option{-mvsx}, @option{-mcpu=power7},
> +@option{-mcpu=power8}) must be enabled to use the IEEE 128-bit
> +floating point support. The IEEE 128-bit floating point support only
> +works on PowerPC Linux systems.
Maybe swap these two? More logical that way I think.
> +The default for @option{-mfloat128-hardware} is enabled on PowerPC
> +Linux systems using the ISA 3.0 instruction set, and disabled on other
> +systems.
You cannot enable it without ISA 3.0, it looks like it does not say that?
The patch looks fine (maybe improve the doc a bit), it's approved for
trunk. Thanks!
Segher