Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 55a63998 authored by Wolfram Strepp's avatar Wolfram Strepp Committed by Linus Torvalds
Browse files

lib/rbtree.c: optimize rb_erase() 



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: default avatarWolfram Strepp <wstrepp@gmx.de>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 53d66608

lib/rbtree.c

+4 −10
Original line number Original line Diff line number Diff line
@@ -163,16 +163,13 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, 
			{

			{

				if (!other->rb_right || rb_is_black(other->rb_right))

				if (!other->rb_right || rb_is_black(other->rb_right))

				{

				{

					struct rb_node *o_left;

					rb_set_black(other->rb_left);

					if ((o_left = other->rb_left))

						rb_set_black(o_left);

					rb_set_red(other);

					rb_set_red(other);

					__rb_rotate_right(other, root);

					__rb_rotate_right(other, root);

					other = parent->rb_right;

					other = parent->rb_right;

				}

				}

				rb_set_color(other, rb_color(parent));

				rb_set_color(other, rb_color(parent));

				rb_set_black(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);

				__rb_rotate_left(parent, root);

				node = root->rb_node;

				node = root->rb_node;
@@ -200,16 +197,13 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, 
			{

			{

				if (!other->rb_left || rb_is_black(other->rb_left))

				if (!other->rb_left || rb_is_black(other->rb_left))

				{

				{

					register struct rb_node *o_right;

					rb_set_black(other->rb_right);

					if ((o_right = other->rb_right))

						rb_set_black(o_right);

					rb_set_red(other);

					rb_set_red(other);

					__rb_rotate_left(other, root);

					__rb_rotate_left(other, root);

					other = parent->rb_left;

					other = parent->rb_left;

				}

				}

				rb_set_color(other, rb_color(parent));

				rb_set_color(other, rb_color(parent));

				rb_set_black(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);

				__rb_rotate_right(parent, root);

				node = root->rb_node;

				node = root->rb_node;