lib/vsprintf.c: improve put_dec_trunc8 slightly

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 <[e-mail]>
Cc: Tejun Heo <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/vsprintf.c

···
 
 /*
  * 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)
···
 out_r:
 	/* 1 <= r < 100 */
 	*((u16 *)buf) = decpair[r];
-	buf += 2;
-	if (buf[-1] == '0')
-		buf--;
+	buf += r < 10 ? 1 : 2;
 	return buf;
 }