linux-kernel - [PATCH 2/2] proc: use do-while in name_to

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Date:   Tue, 12 Sep 2017 22:52:13 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] proc: use do-while in name_to_int()

Gcc doesn't know that "len" is guaranteed to be >=1 by dcache and
generates standard while-loop prologue duplicating loop condition.

	add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-27 (-27)
	function                                     old     new   delta
	name_to_int                                  104      77     -27


Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---

 fs/proc/util.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/proc/util.c
+++ b/fs/proc/util.c
@@ -8,7 +8,7 @@ unsigned name_to_int(const struct qstr *qstr)
 
 	if (len > 1 && *name == '0')
 		goto out;
-	while (len-- > 0) {
+	do {
 		unsigned c = *name++ - '0';
 		if (c > 9)
 			goto out;
@@ -16,7 +16,7 @@ unsigned name_to_int(const struct qstr *qstr)
 			goto out;
 		n *= 10;
 		n += c;
-	}
+	} while (--len > 0);
 	return n;
 out:
 	return ~0U;