This has a slight benefit for x86 and has no effect on other targets.
The benefit to x86 is it change the codegen for setting a node to
block from `mov %r0, %r1; or $RB_BLACK, %r1` to `lea RB_BLACK(%r0),
%r1` which saves an instructions.
In all other cases it just replace ALU with ALU (or -> and) which
perform the same on all machines I am aware of.
Total instructions in rbtree.o:
Before - 802
After - 782
so it saves about 20 `mov` instructions.
Signed-off-by: Noah Goldstein <[email protected]>
---
include/linux/rbtree_augmented.h | 4 ++--
lib/rbtree.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
index d1c53e9d8c75..7ee7ed5de722 100644
--- a/include/linux/rbtree_augmented.h
+++ b/include/linux/rbtree_augmented.h
@@ -156,13 +156,13 @@ RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \
static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
{
- rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
+ rb->__rb_parent_color = rb_color(rb) + (unsigned long)p;
}
static inline void rb_set_parent_color(struct rb_node *rb,
struct rb_node *p, int color)
{
- rb->__rb_parent_color = (unsigned long)p | color;
+ rb->__rb_parent_color = (unsigned long)p + color;
}
static inline void
diff --git a/lib/rbtree.c b/lib/rbtree.c
index c4ac5c2421f2..5114eda6309c 100644
--- a/lib/rbtree.c
+++ b/lib/rbtree.c
@@ -58,7 +58,7 @@
static inline void rb_set_black(struct rb_node *rb)
{
- rb->__rb_parent_color |= RB_BLACK;
+ rb->__rb_parent_color += RB_BLACK;
}
static inline struct rb_node *rb_red_parent(struct rb_node *red)
--
2.34.1