Date: Thu, 13 Jan 2005 16:26:51 -0800 From: "David O'Brien" <obrien@freebsd.org> To: David Gilbert <dgilbert@dclg.ca> Cc: freebsd-alpha@freebsd.org Subject: Re: processor type. Message-ID: <20050114002651.GD29445@dragon.nuxi.com> In-Reply-To: <16866.32790.398095.651691@canoe.dclg.ca> References: <16866.32790.398095.651691@canoe.dclg.ca>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, Jan 10, 2005 at 08:16:06AM -0500, David Gilbert wrote:
> I see in the compiler lines crawling by that gcc is asked to optimize
> for 'EV5' while being compatible with 'EV4'. My Alpha is an EV4 ---
> I'm wondering if I would see better performance with a different flag
> there, but the gcc manual doesn't even acknowledge the existance of
> the options that are in use, let alone the available options.
It doens't???
>From /usr/share/mk/bsd.cpu.mk:
. elif ${MACHINE_ARCH} == "alpha"
_CPUCFLAGS = -mcpu=ev4 -mtune=ev5
http://gcc.gnu.org/onlinedocs/gcc-3.4.3/gcc/DEC-Alpha-Options.html#DEC-Alpha-Options
clearly tells:
-mcpu=cpu_type
Set the instruction set and instruction scheduling parameters for
machine type cpu_type. You can specify either the EV style name or
the corresponding chip number. GCC supports scheduling parameters for
the EV4, EV5 and EV6 family of processors.
-mtune=cpu_type
Set only the instruction scheduling parameters for machine type
cpu_type. The instruction set is not changed.
That said, you should remove the -mtune=ev5 or change it to -mtune=ev4.
My guess is you won't notice a difference, but this this change will
produce the best code for your machine.
--
-- David (obrien@FreeBSD.org)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050114002651.GD29445>