git: 0ee295149ae0 - stable/13 - rb_tree: drop needless tests from rb_next, rb_prev

The branch stable/13 has been updated by dougm:

URL: https://cgit.FreeBSD.org/src/commit/?id=0ee295149ae09a2e486c50dc4d91b433b139c616

commit 0ee295149ae09a2e486c50dc4d91b433b139c616
Author:     Doug Moore <dougm@FreeBSD.org>
AuthorDate: 2022-06-10 21:53:16 +0000
Commit:     Doug Moore <dougm@FreeBSD.org>
CommitDate: 2022-06-19 06:25:00 +0000

    rb_tree: drop needless tests from rb_next, rb_prev
    
    In RB_NEXT, when there is no RB_RIGHT node, the search must proceed
    through the parent node.
    
    There is code written to handle the case when the parent is non-NULL
    and the current element is the left child of that parent. If you
    assume that the current element is either the left child of its
    parent, or the right child of its parent, but not both, then this test
    is not necessary. Instead of assigning RB_PARENT(elm, field) to elm
    when elm == RB_LEFT, removing the test has the code assign
    RB_PARENT(elm, field) to elm when elm != RB_RIGHT. There's no need to
    examine the RB_LEFT field at all.
    
    This change removes that needless RB_LEFT test, and makes a similar
    change to the RB_PREV implementation.
    
    Reviewed by:    alc
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D35450
    
    (cherry picked from commit 36447829aee545ad9eafbfff3a783ee58cfb28fd)
---
 sys/sys/tree.h | 22 ++++++----------------
 1 file changed, 6 insertions(+), 16 deletions(-)

diff --git a/sys/sys/tree.h b/sys/sys/tree.h
index eb5f244d8a12..4cdd9548ba62 100644
--- a/sys/sys/tree.h
+++ b/sys/sys/tree.h
@@ -719,15 +719,10 @@ name##_RB_NEXT(struct type *elm)					\
 		while (RB_LEFT(elm, field))				\
 			elm = RB_LEFT(elm, field);			\
 	} else {							\
-		if (RB_PARENT(elm, field) &&				\
-		    (elm == RB_LEFT(RB_PARENT(elm, field), field)))	\
-			elm = RB_PARENT(elm, field);			\
-		else {							\
-			while (RB_PARENT(elm, field) &&			\
-			    (elm == RB_RIGHT(RB_PARENT(elm, field), field)))\
-				elm = RB_PARENT(elm, field);		\
+		while (RB_PARENT(elm, field) &&				\
+		    (elm == RB_RIGHT(RB_PARENT(elm, field), field)))	\
 			elm = RB_PARENT(elm, field);			\
-		}							\
+		elm = RB_PARENT(elm, field);				\
 	}								\
 	return (elm);							\
 }
@@ -742,15 +737,10 @@ name##_RB_PREV(struct type *elm)					\
 		while (RB_RIGHT(elm, field))				\
 			elm = RB_RIGHT(elm, field);			\
 	} else {							\
-		if (RB_PARENT(elm, field) &&				\
-		    (elm == RB_RIGHT(RB_PARENT(elm, field), field)))	\
-			elm = RB_PARENT(elm, field);			\
-		else {							\
-			while (RB_PARENT(elm, field) &&			\
-			    (elm == RB_LEFT(RB_PARENT(elm, field), field)))\
-				elm = RB_PARENT(elm, field);		\
+		while (RB_PARENT(elm, field) &&				\
+		    (elm == RB_LEFT(RB_PARENT(elm, field), field)))	\
 			elm = RB_PARENT(elm, field);			\
-		}							\
+		elm = RB_PARENT(elm, field);				\
 	}								\
 	return (elm);							\
 }