The patch titled
lib/rbtree.c: optimize rb_erase()
has been added to the -mm tree. Its filename is
lib-rbtreec-optimize-rb_erase.patch
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------------------------------------------------------
Subject: lib/rbtree.c: optimize rb_erase()
From: "Wolfram Strepp" <wstrepp@xxxxxx>
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@xxxxxx>
Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Andrea Arcangeli <andrea@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/rbtree.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
diff -puN lib/rbtree.c~lib-rbtreec-optimize-rb_erase lib/rbtree.c
--- a/lib/rbtree.c~lib-rbtreec-optimize-rb_erase
+++ a/lib/rbtree.c
@@ -163,17 +163,14 @@ static void __rb_erase_color(struct rb_n
{
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;
@@ -200,17 +197,14 @@ static void __rb_erase_color(struct rb_n
{
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;
_
Patches currently in -mm which might be from wstrepp@xxxxxx are
lib-rbtreec-optimize-rb_erase.patch
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