Messages in this thread | | | From | Michal Nazarewicz <> | Subject | Re: [PATCH 2/3] lib: vsprintf: optimised put_dec() for 32-bit machines | Date | Fri, 06 Aug 2010 09:08:11 +0200 |
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Denys Vlasenko <vda.linux@googlemail.com> writes:
> On Friday 06 August 2010 00:38, Michal Nazarewicz wrote: >> The disadvantage is that the proposed function is 2.5-3.5 bigger. >> Those are not big functions though -- we are talking here about >> proposed function being below 512.
> It's a slippery slope. Here's where it ends: glibc > has memcpy() function which is "only" 8k of code or so. > I'm not joking.
I'm aware of that. I assume that someone more clever then me will decide whether to accept this patch or not. (Also we win a few bytes on put_dec_full() and put_dec_8bit()). :P
>> +#if BITS_PER_LONG == 64 >> + > ... >> +#else > ... >> +/* >> + * Based on code by Douglas W. Jones found at >> + * <http://www.cs.uiowa.edu/~jones/bcd/decimal.html#sixtyfour>. This >> + * performs no 64-bit division and hence should be faster on 32-bit >> + * machines then the version of the function above. >> + */ >> +static noinline_for_stack >> +char *put_dec(char *buf, unsigned long long n) >> +{ >> + uint32_t d3, d2, d1, q; >> + >> + if (!n) { >> + *buf++ = '0'; >> + return buf; >> + } >> + >> + d1 = (n >> 16) & 0xFFFF; >> + d2 = (n >> 32) & 0xFFFF; >> + d3 = (n >> 48) & 0xFFFF; > > Are you assuming that sizeof(long long) == 8, always?
Well... yes. C requires long long to be at least 64-bit and I don't see it being larger in any foreseeable feature. Wouldn't it be enough to put a static assert here?
-- Best regards, _ _ .o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michal "mina86" Nazarewicz (o o) ooo +--<mina86-tlen.pl>--<jid:mina86-jabber.org>--ooO--(_)--Ooo--
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