From 61c74fb66f1bef776923cbd5b2a62fb06b003f0c Mon Sep 17 00:00:00 2001
From: Doug Moore <dougm@FreeBSD.org>
Date: Sat, 25 Jun 2022 02:40:16 -0500
Subject: [PATCH] rb_tree: optimize tree rotation

The RB_ROTATE macros begin with fetching a field via a pointer. In
most cases, that value is one that has already been pulled into a
register, and the compiler cannot infer that. So, to eliminate those
needless fetches, have the caller of the RB_ROTATE macros present the
data in the third macro parameter, rather than having the macro fetch
it.

Differential Revision:	https://reviews.freebsd.org/D35520
---
 sys/sys/tree.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sys/sys/tree.h b/sys/sys/tree.h
index 0403288d1d68..fb0136a0c69a 100644
--- a/sys/sys/tree.h
+++ b/sys/sys/tree.h
@@ -380,7 +380,6 @@ struct {								\
 } while (/*CONSTCOND*/ 0)
 
 #define RB_ROTATE_LEFT(head, elm, tmp, field) do {			\
-	(tmp) = RB_RIGHT(elm, field);					\
 	if ((RB_RIGHT(elm, field) = RB_LEFT(tmp, field)) != NULL) {	\
 		RB_SET_PARENT(RB_RIGHT(elm, field), elm, field);	\
 	}								\
@@ -392,7 +391,6 @@ struct {								\
 } while (/*CONSTCOND*/ 0)
 
 #define RB_ROTATE_RIGHT(head, elm, tmp, field) do {			\
-	(tmp) = RB_LEFT(elm, field);					\
 	if ((RB_LEFT(elm, field) = RB_RIGHT(tmp, field)) != NULL) {	\
 		RB_SET_PARENT(RB_LEFT(elm, field), elm, field);		\
 	}								\
@@ -473,6 +471,7 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm)		\
 			}						\
 			RB_FLIP_RIGHT(parent, field);			\
 			if (RB_RED_RIGHT(parent, field)) {		\
+				child = elm;				\
 				elm = parent;				\
 				continue;				\
 			}						\
@@ -493,6 +492,7 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm)		\
 			}						\
 			RB_FLIP_LEFT(parent, field);			\
 			if (RB_RED_LEFT(parent, field)) {		\
+				child = elm;				\
 				elm = parent;				\
 				continue;				\
 			}						\
@@ -548,6 +548,7 @@ name##_RB_REMOVE_COLOR(struct name *head,				\
 				RB_FLIP_LEFT(parent, field);		\
 			else if (!RB_RED_RIGHT(sib, field)) {		\
 				RB_FLIP_LEFT(parent, field);		\
+				elm = RB_LEFT(sib, field);		\
 				RB_ROTATE_RIGHT(head, sib, elm, field);	\
 				if (RB_RED_RIGHT(elm, field))		\
 					RB_FLIP_LEFT(sib, field);	\
@@ -578,6 +579,7 @@ name##_RB_REMOVE_COLOR(struct name *head,				\
 				RB_FLIP_RIGHT(parent, field);		\
 			else if (!RB_RED_LEFT(sib, field)) {		\
 				RB_FLIP_RIGHT(parent, field);		\
+				elm = RB_RIGHT(sib, field);		\
 				RB_ROTATE_LEFT(head, sib, elm, field);	\
 				if (RB_RED_LEFT(elm, field))		\
 					RB_FLIP_RIGHT(sib, field);	\