Messages in this thread | | | Date | Thu, 17 Apr 2003 10:32:02 -0400 | From | Jeff Garzik <> | Subject | Re: [BK+PATCH] remove __constant_memcpy |
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On Thu, Apr 17, 2003 at 02:17:16PM +0100, Alan Cox wrote: > On Iau, 2003-04-17 at 01:57, Jeff Garzik wrote: > > The patch below is the conservative, obvious patch. It only kicks in > > when __builtin_constant_p() is true, and it only applies to the i386 > > arch. > > You are assuming the compiler is smart about stuff - it doesnt know > SSE/MMX for page copies etc. For small copies it should alays win, but
Prior to my patch, __constant_memcpy was -already- only used for small, constant-size copies.
Therefore, my patch applied __builtin_memcpy only to small, constant-size copies. The existing kernel custom-memcpy code continued to perform as expected.
You and Linus both seem to think MMX/SSE/SSE2 is somehow in the equation, but I do not see that at all. I left those paths alone. Clarification/LART requested...
> isn't it best if so to use __builtin_memcpy without our existing > macros not just trust the compiler ?
hum, I didn't parse this at all: Use of __builtin_memcpy implies trusting the compiler :)
Maybe you meant s/without/with/ ?
Jeff
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