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>
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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)
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