From d03eaf36dc30bf41fc57f8de100c105f49063429 Mon Sep 17 00:00:00 2001
From: dougm <dougm@FreeBSD.org>
Date: Sat, 20 Jun 2020 20:25:39 +0000
Subject: [PATCH] In concluding RB_REMOVE_COLOR, in the case when

the sibling of the root of the too-short tree is black and at least one of the
children of that sibling is red, either one or two rotations finish the
rebalancing. In the case when both of the children are red, the current
implementation uses two rotations where only one is necessary. This change
removes that extra rotation, and in that case also removes a needless
black-to-red-to-black recoloring.

Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D25335
---
 newlib/libc/include/sys/tree.h | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/newlib/libc/include/sys/tree.h b/newlib/libc/include/sys/tree.h
index 372c001b9..2e1cc1eda 100644
--- a/newlib/libc/include/sys/tree.h
+++ b/newlib/libc/include/sys/tree.h
@@ -493,21 +493,19 @@ name##_RB_REMOVE_COLOR(struct name *head, struct type *parent)		\
 				RB_ROTATE_LEFT(head, parent, tmp, field);\
 				tmp = RB_RIGHT(parent, field);		\
 			}						\
-			if (RB_ISRED(RB_LEFT(tmp, field), field)) {	\
+			if (RB_ISRED(RB_RIGHT(tmp, field), field))	\
+				RB_COLOR(RB_RIGHT(tmp, field), field) = RB_BLACK; \
+			else if (RB_ISRED(RB_LEFT(tmp, field), field)) { \
 				struct type *oleft;			\
-				oleft = RB_LEFT(tmp, field);		\
-				RB_COLOR(oleft, field) = RB_BLACK;	\
-				RB_COLOR(tmp, field) = RB_RED;		\
 				RB_ROTATE_RIGHT(head, tmp, oleft, field); \
-				tmp = RB_RIGHT(parent, field);		\
-			} else if (!RB_ISRED(RB_RIGHT(tmp, field), field)) { \
+				RB_COLOR(oleft, field) = RB_BLACK;	\
+				tmp = oleft;				\
+			} else {					\
 				RB_COLOR(tmp, field) = RB_RED;		\
 				elm = parent;				\
 				parent = RB_PARENT(elm, field);		\
 				continue;				\
 			}						\
-			if (RB_ISRED(RB_RIGHT(tmp, field), field))	\
-				RB_COLOR(RB_RIGHT(tmp, field), field) = RB_BLACK; \
 			RB_COLOR(tmp, field) = RB_COLOR(parent, field);	\
 			RB_COLOR(parent, field) = RB_BLACK;		\
 			RB_ROTATE_LEFT(head, parent, tmp, field);	\
@@ -520,21 +518,19 @@ name##_RB_REMOVE_COLOR(struct name *head, struct type *parent)		\
 				RB_ROTATE_RIGHT(head, parent, tmp, field);\
 				tmp = RB_LEFT(parent, field);		\
 			}						\
-			if (RB_ISRED(RB_RIGHT(tmp, field), field)) {	\
+			if (RB_ISRED(RB_LEFT(tmp, field), field))	\
+				RB_COLOR(RB_LEFT(tmp, field), field) = RB_BLACK; \
+			else if (RB_ISRED(RB_RIGHT(tmp, field), field)) { \
 				struct type *oright;			\
-				oright = RB_RIGHT(tmp, field);		\
-				RB_COLOR(oright, field) = RB_BLACK;	\
-				RB_COLOR(tmp, field) = RB_RED;		\
 				RB_ROTATE_LEFT(head, tmp, oright, field); \
-				tmp = RB_LEFT(parent, field);		\
+				RB_COLOR(oright, field) = RB_BLACK;	\
+				tmp = oright;				\
 			} else if (!RB_ISRED(RB_LEFT(tmp, field), field)) { \
 				RB_COLOR(tmp, field) = RB_RED;		\
 				elm = parent;				\
 				parent = RB_PARENT(elm, field);		\
 				continue;				\
 			}						\
-			if (RB_ISRED(RB_LEFT(tmp, field), field))	\
-				RB_COLOR(RB_LEFT(tmp, field), field) = RB_BLACK; \
 			RB_COLOR(tmp, field) = RB_COLOR(parent, field);	\
 			RB_COLOR(parent, field) = RB_BLACK;		\
 			RB_ROTATE_RIGHT(head, parent, tmp, field);	\