lib/vsprintf.c: improve put_dec_trunc8 slightly (675cf53c) · Commits · 戴 / test

I hadn't had enough coffee when I wrote this. Currently, the final increment of buf depends on the value loaded from the table, and causes gcc to emit a cmov immediately before the return. It is smarter to let it depend on r, since the increment can then be computed in parallel with the final load/store pair. It also shaves 16 bytes of .text. Signed-off-by:

Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:

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

Linus Torvalds <torvalds@linux-foundation.org>

lib/vsprintf.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -165,9 +165,9 @@ static const u16 decpair[100] = {

		/*
		* This will print a single '0' even if r == 0, since we would
		* immediately jump to out_r where two 0s would be written and one of
		* them then discarded. This is needed by ip4_string below. All other
		* callers pass a non-zero value of r.
		* immediately jump to out_r where two 0s would be written but only
		* one of them accounted for in buf. This is needed by ip4_string
		* below. All other callers pass a non-zero value of r.
		*/
		static noinline_for_stack
		char put_dec_trunc8(char buf, unsigned r)
		@@ -206,9 +206,7 @@ out_q:
		out_r:
		/* 1 <= r < 100 */
		((u16 )buf) = decpair[r];
		buf += 2;
		if (buf[-1] == '0')
		buf--;
		buf += r < 10 ? 1 : 2;
		return buf;
		}

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