From 9db2b545710ad398a9012094d33b7e8884013227 Mon Sep 17 00:00:00 2001
From: dougm <dougm@FreeBSD.org>
Date: Thu, 21 May 2020 05:34:02 +0000
Subject: [PATCH] For the case when RB_REMOVE requires a nontrivial

search to find the node to replace the one being removed, restructure to first
remove the replacement node and correct the parent pointers around it, and then
let the all-cases code at the end deal with the parent of the deleted node,
making it point to the replacement node. This removes one or two conditional
branches.

Reviewed by:	markj
Tested by:	pho
Differential Revision:	https://reviews.freebsd.org/D24845
---
 newlib/libc/include/sys/tree.h | 52 ++++++++++++++++------------------
 1 file changed, 24 insertions(+), 28 deletions(-)

diff --git a/newlib/libc/include/sys/tree.h b/newlib/libc/include/sys/tree.h
index 5c31ff2ea..b1e5e23a7 100644
--- a/newlib/libc/include/sys/tree.h
+++ b/newlib/libc/include/sys/tree.h
@@ -562,48 +562,44 @@ name##_RB_REMOVE_COLOR(struct name *head, struct type *parent, struct type *elm)
 attr struct type *							\
 name##_RB_REMOVE(struct name *head, struct type *elm)			\
 {									\
-	struct type *child, *parent, *old = elm;			\
+	struct type *child, *parent, *parent_old, *old = elm;		\
 	int color;							\
-	if (RB_LEFT(elm, field) == NULL)				\
-		child = RB_RIGHT(elm, field);				\
-	else if (RB_RIGHT(elm, field) == NULL)				\
-		child = RB_LEFT(elm, field);				\
-	else {								\
+	parent_old = parent = RB_PARENT(elm, field);			\
+	color = RB_COLOR(elm, field);					\
+	if (RB_LEFT(elm, field) == NULL) {				\
+		elm = child = RB_RIGHT(elm, field);			\
+		if (elm != NULL)					\
+			RB_PARENT(elm, field) = parent;			\
+	} else if (RB_RIGHT(elm, field) == NULL) {			\
+		elm = child = RB_LEFT(elm, field);			\
+		RB_PARENT(elm, field) = parent;				\
+	} else {							\
 		elm = RB_RIGHT(old, field);				\
 		if ((child = RB_LEFT(elm, field)) == NULL) {		\
 			child = RB_RIGHT(elm, field);			\
 			RB_RIGHT(old, field) = child;			\
-			RB_PARENT(elm, field) = elm;			\
+			parent = elm;					\
 		} else {						\
 			do						\
 				elm = child;				\
 			while ((child = RB_LEFT(elm, field)) != NULL);	\
 			child = RB_RIGHT(elm, field);			\
+			parent = RB_PARENT(elm, field);			\
+			RB_LEFT(parent, field) = child;			\
+			if (child != NULL)				\
+				RB_PARENT(child, field) = parent;	\
 			RB_PARENT(RB_RIGHT(old, field), field) = elm;	\
 		}							\
 		RB_PARENT(RB_LEFT(old, field), field) = elm;		\
-		parent = RB_PARENT(old, field);				\
-		if (parent != NULL) {					\
-			if (RB_LEFT(parent, field) == old)		\
-				RB_LEFT(parent, field) = elm;		\
-			else						\
-				RB_RIGHT(parent, field) = elm;		\
-		} else							\
-			RB_ROOT(head) = elm;				\
+		color = RB_COLOR(elm, field);				\
+		elm->field = old->field;				\
 	}								\
-	parent = RB_PARENT(elm, field);					\
-	color = RB_COLOR(elm, field);					\
-	if (child != NULL)						\
-		RB_PARENT(child, field) = parent;			\
-	if (parent != NULL) {						\
-		if (RB_LEFT(parent, field) == elm)			\
-			RB_LEFT(parent, field) = child;			\
-		else							\
-			RB_RIGHT(parent, field) = child;		\
-	} else								\
-		RB_ROOT(head) = child;					\
-	if (elm != old)							\
-		(elm)->field = (old)->field;				\
+	if (parent_old == NULL)						\
+		RB_ROOT(head) = elm;					\
+	else if (RB_LEFT(parent_old, field) == old)			\
+		RB_LEFT(parent_old, field) = elm;			\
+	else								\
+		RB_RIGHT(parent_old, field) = elm;			\
 	if (color == RB_BLACK)						\
 		name##_RB_REMOVE_COLOR(head, parent, child);		\
 	while (parent != NULL) {					\