[PATCH] x86_64: Optimize bitmap_weight for small bitmaps
Use inline code bitmaps <= BITS_PER_LONG in bitmap_weight. This
gives _much_ better code.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index d9ed279..dcc5de7 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -24,6 +24,9 @@
* The available bitmap operations and their rough meaning in the
* case that the bitmap is a single unsigned long are thus:
*
+ * Note that nbits should be always a compile time evaluable constant.
+ * Otherwise many inlines will generate horrible code.
+ *
* bitmap_zero(dst, nbits) *dst = 0UL
* bitmap_fill(dst, nbits) *dst = ~0UL
* bitmap_copy(dst, src, nbits) *dst = *src
@@ -244,6 +247,8 @@
static inline int bitmap_weight(const unsigned long *src, int nbits)
{
+ if (nbits <= BITS_PER_LONG)
+ return hweight_long(*src & BITMAP_LAST_WORD_MASK(nbits));
return __bitmap_weight(src, nbits);
}