Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit cb239d0a authored by George Spelvin's avatar George Spelvin Committed by Linus Torvalds
Browse files

lib: vsprintf: optimize put_dec_trunc8() 



If you're going to have a conditional branch after each 32x32->64-bit
multiply, might as well shrink the code and make it a loop.

This also avoids using the long multiply for small integers.

(This leaves the comments in a confusing state, but that's a separate
patch to make review easier.)

Signed-off-by: default avatarGeorge Spelvin <linux@horizon.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Rabin Vincent <rabin@rab.in>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2359172a

lib/vsprintf.c

+6 −16
Original line number Diff line number Diff line
@@ -174,22 +174,12 @@ char *put_dec_trunc8(char *buf, unsigned r) 
	unsigned q;



	/* Copy of previous function's body with added early returns */

	q      = (r * (uint64_t)0x1999999a) >> 32;

	*buf++ = (r - 10 * q) + '0'; /* 2 */

	if (q == 0)

		return buf;

	r      = (q * (uint64_t)0x1999999a) >> 32;

	*buf++ = (q - 10 * r) + '0'; /* 3 */

	if (r == 0)

		return buf;

	q      = (r * (uint64_t)0x1999999a) >> 32;

	*buf++ = (r - 10 * q) + '0'; /* 4 */

	if (q == 0)

		return buf;

	r      = (q * (uint64_t)0x1999999a) >> 32;

	*buf++ = (q - 10 * r) + '0'; /* 5 */

	if (r == 0)

		return buf;

	while (r >= 10000) {

		q = r + '0';

		r  = (r * (uint64_t)0x1999999a) >> 32;

		*buf++ = q - 10*r;

	}



	q      = (r * 0x199a) >> 16;

	*buf++ = (r - 10 * q)  + '0'; /* 6 */

	if (q == 0)