lib: vsprintf: optimize put_dec_trunc8() (cb239d0a) · Commits · 戴 / test

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:

George 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:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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 - 10r;
		}

		q = (r * 0x199a) >> 16;
		buf++ = (r - 10 q) + '0'; /* 6 */
		if (q == 0)

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