[117/147] find: micro-optimize for_each_{set,clear}_bit()

Commit Message

Andrew Morton Sept. 8, 2021, 2:59 a.m. UTC

From: Yury Norov <[e-mail]>
Subject: 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().

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Yury Norov <[e-mail]>
Tested-by: Wolfram Sang <[e-mail]>
Cc: Alexander Lobakin <[e-mail]>
Cc: Alexey Klimov <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: Dennis Zhou <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Ulf Hansson <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/find.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Patch

--- a/include/linux/find.h~find-micro-optimize-for_each_setclear_bit
+++ a/include/linux/find.h
@@ -280,7 +280,7 @@  unsigned long find_next_bit_le(const voi
 #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 voi
 	     (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))