lib/rbtree.c: optimize rb_erase() (55a63998) · Commits · 戴 / test

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>

lib/rbtree.c

+4 −10

Original line number	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))
		{
		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_rotate_left(parent, root);
		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))
		{
		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_rotate_right(parent, root);
		node = root->rb_node;

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