linux-kernel - [PATCH 4/4] lib/vsprintf.c: Another small hack

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Message-Id: <1424474479-25543-5-git-send-email-linux@rasmusvillemoes.dk>
Date:	Sat, 21 Feb 2015 00:21:19 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] lib/vsprintf.c: Another small hack

Making ZEROPAD == '0'-' ', we can eliminate a few more instructions.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 lib/vsprintf.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7a299d43987a..2753f9261115 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -341,10 +341,10 @@ int num_to_str(char *buf, int size, unsigned long long num)
 }
 
 #define SIGN	1		/* unsigned/signed, must be 1 */
-#define ZEROPAD	2		/* pad with zero */
+#define LEFT	2		/* left justified */
 #define PLUS	4		/* show plus */
 #define SPACE	8		/* space if plus */
-#define LEFT	16		/* left justified */
+#define ZEROPAD	16		/* pad with zero, must be 16 == '0' - ' ' */
 #define SMALL	32		/* use lowercase in hex (must be 32 == 0x20) */
 #define SPECIAL	64		/* prefix hex with "0x", octal with "0" */
 
@@ -467,7 +467,8 @@ char *number(char *buf, char *end, unsigned long long num,
 	}
 	/* zero or space padding */
 	if (!(spec.flags & LEFT)) {
-		char c = (spec.flags & ZEROPAD) ? '0' : ' ';
+		char c = ' ' + (spec.flags & ZEROPAD);
+		BUILD_BUG_ON(' ' + ZEROPAD != '0');
 		while (--spec.field_width >= 0) {
 			if (buf < end)
 				*buf = c;
-- 
2.1.3

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