linux-kernel - [PATCH 2/3] find: micro-optimize for_each_{set,clear}

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Date:   Fri, 18 Jun 2021 12:57:34 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Marc Zyngier <maz@...nel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Alexey Klimov <aklimov@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, etnaviv@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-hwmon@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>
Subject: [PATCH 2/3] find: micro-optimize for_each_{set,clear}_bit()

The macros iterate thru all set/clear bits in a bitmap. They search a
first bit using find_first_bit(), and the rest bits using find_next_bit().

Since find_next_bit() is called shortly after find_first_bit(), we can
save few lines of I-cache by not using find_first_bit().

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 include/linux/find.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/find.h b/include/linux/find.h
index 4500e8ab93e2..ae9ed52b52b8 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -280,7 +280,7 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 #endif
 
 #define for_each_set_bit(bit, addr, size) \
-	for ((bit) = find_first_bit((addr), (size));		\
+	for ((bit) = find_next_bit((addr), (size), 0);		\
 	     (bit) < (size);					\
 	     (bit) = find_next_bit((addr), (size), (bit) + 1))
 
@@ -291,7 +291,7 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 	     (bit) = find_next_bit((addr), (size), (bit) + 1))
 
 #define for_each_clear_bit(bit, addr, size) \
-	for ((bit) = find_first_zero_bit((addr), (size));	\
+	for ((bit) = find_next_zero_bit((addr), (size), 0);	\
 	     (bit) < (size);					\
 	     (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
 
-- 
2.30.2