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SubjectRe: [PATCH 2/3] lib: vsprintf: optimised put_dec() for 32-bit machines
Date
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.



> +#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?

--
vda


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