core/rbtree: optimize rb_erase()
See kernel commit 55a63998b8967615a15e2211ba0ff3a84a565824
----
Tfour 4 redundant if-conditions in function __rb_erase_color() in
lib/rbtree.c are removed.
In pseudo-source-code, the structure of the code is as follows:
if ((!A || B) && (!C || D)) {
.
.
.
} else {
if (!C || D) {//if this is true, it implies: (A == true) && (B == false)
if (A) {//hence this always evaluates to 'true'...
.
}
.
//at this point, C always becomes true, because of:
__rb_rotate_right/left();
//and:
other = parent->rb_right/left;
}
.
.
if (C) {//...and this too !
.
}
}
Signed-off-by: Wolfram Strepp <wstrepp@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
----
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/src/rbtree.c b/src/rbtree.c
index 9b7fe83..d1c2f6b 100644
--- a/src/rbtree.c
+++ b/src/rbtree.c
@@ -161,17 +161,14 @@
{
if (!other->rb_right || rb_is_black(other->rb_right))
{
- struct rb_node *o_left;
- if ((o_left = other->rb_left))
- rb_set_black(o_left);
+ rb_set_black(other->rb_left);
rb_set_red(other);
__rb_rotate_right(other, root);
other = parent->rb_right;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
- if (other->rb_right)
- rb_set_black(other->rb_right);
+ rb_set_black(other->rb_right);
__rb_rotate_left(parent, root);
node = root->rb_node;
break;
@@ -198,17 +195,14 @@
{
if (!other->rb_left || rb_is_black(other->rb_left))
{
- register struct rb_node *o_right;
- if ((o_right = other->rb_right))
- rb_set_black(o_right);
+ rb_set_black(other->rb_right);
rb_set_red(other);
__rb_rotate_left(other, root);
other = parent->rb_left;
}
rb_set_color(other, rb_color(parent));
rb_set_black(parent);
- if (other->rb_left)
- rb_set_black(other->rb_left);
+ rb_set_black(other->rb_left);
__rb_rotate_right(parent, root);
node = root->rb_node;
break;