Re: [PATCH] 498+ days uptime

H. Peter Anvin (hpa@transmeta.com)
26 Aug 1998 07:37:34 GMT

Followup to: <35E316CB.A9E09B15@gmx.de>
By author: Edgar Toernig <froese@gmx.de>
In newsgroup: linux.dev.kernel
>
> But the worst thing is register usage. The x86 has very few registers
> and 64-bit arithmetic requires a lot. So, gcc has to generate a
> lot of code just to shuffle register contents. Nearly every 64-bit
> operator has to flush all registers to the stack and restore them
> later. And this makes a difference in execution time and memory
> usage...
>

Actually, on x86 64-bit arithmetric is quite cheap, because x86 with
its 8-bit CPU heritage has explicit support for multiword arithmetric
(adc, sbb, 64-bit mul/imul/div/idiv).

-hpa

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