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Re: [RFC] Optimize swab operations on mips_r2 cpu

To: Franck <>
Subject: Re: [RFC] Optimize swab operations on mips_r2 cpu
From: Nigel Stephens <>
Date: Fri, 27 Jan 2006 13:45:51 +0000
Cc: "Kevin D. Kissell" <>,
In-reply-to: <>
Organization: MIPS Technologies
Original-recipient: rfc822;
References: <> <> <> <> <005101c6228c$6ebfb0a0$10eca8c0@grendel> <> <> <> <> <> <>
User-agent: Debian Thunderbird 1.0.2 (X11/20050817)

Franck wrote:

2006/1/26, Nigel Stephens <>:
You could, but why not stick with -march=4ksd if that's your CPU of
choice? It appears to result in  marginally smaller code even when using
-Os, and should have (slightly) better performance than a generic
mips32r2 kernel?

Just to avoid a new CPU_4KSD definition in the kernel code as
suggested by Kevin. Basically all mips32r2 specific code is the same
as 4ksd specific code (except the code that deals with SmartMIPS
extension). So it can use CONFIG_CPU_MIPS32_R2 macro.

Not that I'm a Linux hacker, but aren't those separate things? Can't you compile with -march=4ksd to get the CPU-specific compiler optimisations, but then use the more generic CONFIG_CPU_MIPSR2 and/or CONFIG_CPU_SMARTMIPS to select the appropriate code inside the kernel source (i.e. no need for CONFIG_CPU_4KSD)?


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