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Subject[PATCH] lib: Avoid redundant sizeof checking in __bitmap_weight() calculation.
Date
Currently, during __bitmap_weight() calculation hweight_long() is used.
Inside a hweight_long() a check has been made to figure out whether a
hweight32() or hweight64() version to use.

However, it's unnecessary to do it in case of __bitmap_weight() calculation
inside the loop. We can detect whether to use hweight32() or hweight64()
upfront and call respective function directly. It also reduces the
vmlinux size.

Before the patch:
text data bss dec hex filename
12901332 7798930 14541816 35242078 219c05e vmlinux

After the patch:
text data bss dec hex filename
12901331 7798930 14541816 35242077 219c05d vmlinux

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Yury Norov <ynorov@caviumnetworks.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>

---
Patch was created against torvald's tree (commit 43ff2f4db9d0f764).

lib/bitmap.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index d8f0c09..552096f 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -241,10 +241,15 @@ EXPORT_SYMBOL(__bitmap_subset);
int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
{
unsigned int k, lim = bits/BITS_PER_LONG;
- int w = 0;
-
- for (k = 0; k < lim; k++)
- w += hweight_long(bitmap[k]);
+ int w = 0, is32 = sizeof(bitmap[0]) ? 1 : 0;
+
+ if (is32) {
+ for (k = 0; k < lim; k++)
+ w += hweight32(bitmap[k]);
+ } else {
+ for (k = 0; k < lim; k++)
+ w += hweight64(bitmap[k]);
+ }

if (bits % BITS_PER_LONG)
w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
--
2.9.3
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