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For the case when RB_REMOVE requires a nontrivial search to find the

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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
This commit is contained in:
Doug Moore 2020-05-21 05:34:02 +00:00
parent a100c050eb
commit c807b9ec06
1 changed files with 24 additions and 28 deletions
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52
sys/sys/tree.h
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@ -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) { \