| Message ID | 20170617093253.3990-3-kpraveen.lkml@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, 2017-06-17 at 15:02 +0530, Praveen Kumar wrote: > 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> > [Linux commit 55a63998b8967615a15e2211ba0ff3a84a565824] > > Ported to Xen. > > Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com> > Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com> Dario
diff --git a/xen/common/rbtree.c b/xen/common/rbtree.c index d86b5f25c0..70cb15f1fe 100644 --- a/xen/common/rbtree.c +++ b/xen/common/rbtree.c @@ -162,17 +162,14 @@ 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_set_black(other->rb_right); __rb_rotate_left(parent, root); node = root->rb_node; break; @@ -199,17 +196,14 @@ 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_set_black(other->rb_left); __rb_rotate_right(parent, root); node = root->rb_node; break;
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> [Linux commit 55a63998b8967615a15e2211ba0ff3a84a565824] Ported to Xen. Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com> --- xen/common/rbtree.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-)