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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
This commit is contained in:
dougm 2020-06-20 20:25:39 +00:00 committed by Sebastian Huber
parent 977a827d29
commit d03eaf36dc
1 changed files with 11 additions and 15 deletions
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26
newlib/libc/include/sys/tree.h
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@ -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); \