Messages in this thread | | | From | Michal Nazarewicz <> | Subject | Re: [PATCH 2/4] lib: vsprintf: Optimize division by 10000 | Date | Mon, 24 Sep 2012 14:41:32 +0200 |
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On Mon, Sep 24 2012, George Spelvin wrote: >> You are using a 64-bit multiply in a path that is designed for 32-bit >> processors, which makes me feel that it will be slower. > > Slower than the divide it's replacing?
OK, granted, it might be faster after all. ;) Still, I'd love to see some benchmark.
> The following 32-bit processors have 32x32->64-bit multiply: > > x86 > ARM (as of ARMv4 = ARM7TDMI, the lowest version in common use) > SPARCv7, SPARCv8
Didn't some SPARCs have 32x32->32 multiply? I remember reading some rant from a GMP developer about how SPARC is broken that way.
> MIPS32 > MC68020 > PA-RISC 1.1 (XMPYU) > avr32 > PowerPC (MULHWU) > VAX (EMUL)
> I could do some Kconfig hacking and make the code path > architecture-dependent. Do you think it's worth it?
Definitely not.
-- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo--[unhandled content-type:application/pgp-signature] | |