Patchwork drivers/sbus/char: Micro-optimization in display7seg.c

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Submitter Rasmus Villemoes
Date June 19, 2014, 12:31 p.m.
Message ID <1403181112-12018-1-git-send-email-linux@rasmusvillemoes.dk>
Download mbox | patch
Permalink /patch/361855/
State Accepted
Delegated to: David Miller
Headers show

Comments

Rasmus Villemoes - June 19, 2014, 12:31 p.m.
Flipping a bit doesn't need four lines of code; and gcc seems to
actually generate two branches.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 drivers/sbus/char/display7seg.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
David Miller - July 22, 2014, 4:38 a.m.
From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Date: Thu, 19 Jun 2014 14:31:52 +0200

> Flipping a bit doesn't need four lines of code; and gcc seems to
> actually generate two branches.
> 
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>

Applied to sparc-next
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Patch

diff --git a/drivers/sbus/char/display7seg.c b/drivers/sbus/char/display7seg.c
index 7c71e7b..3221dff 100644
--- a/drivers/sbus/char/display7seg.c
+++ b/drivers/sbus/char/display7seg.c
@@ -143,10 +143,7 @@  static long d7s_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 	case D7SIOCTM:
 		/* toggle device mode-- flip display orientation */
-		if (regs & D7S_FLIP)
-			regs &= ~D7S_FLIP;
-		else
-			regs |= D7S_FLIP;
+		regs ^= D7S_FLIP;
 		writeb(regs, p->regs);
 		break;
 	}