Commit b0687c11 authored by Noah Goldstein's avatar Noah Goldstein Committed by Andrew Morton
Browse files

lib/rbtree: use '+' instead of '|' for setting color. 

This has a slight benefit for x86 and has no effect on other targets.

The benefit to x86 is it change the codegen for setting a node to block
from `mov %r0, %r1; or $RB_BLACK, %r1` to `lea RB_BLACK(%r0), %r1` which
saves an instructions.

In all other cases it just replace ALU with ALU (or -> and) which
perform the same on all machines I am aware of.

Total instructions in rbtree.o:
    Before  - 802
    After   - 782

so it saves about 20 `mov` instructions.

Link: https://lkml.kernel.org/r/20230404221350.3806566-1-goldstein.w.n@gmail.com


Signed-off-by: default avatarNoah Goldstein <goldstein.w.n@gmail.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 1be2edb2

include/linux/rbtree_augmented.h

+2 −2
Original line number Diff line number Diff line
@@ -156,13 +156,13 @@ RB_DECLARE_CALLBACKS(RBSTATIC, RBNAME, \ 


static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)

{

	rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;

	rb->__rb_parent_color = rb_color(rb) + (unsigned long)p;

}



static inline void rb_set_parent_color(struct rb_node *rb,

				       struct rb_node *p, int color)

{

	rb->__rb_parent_color = (unsigned long)p | color;

	rb->__rb_parent_color = (unsigned long)p + color;

}



static inline void

lib/rbtree.c

+1 −1
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ 


static inline void rb_set_black(struct rb_node *rb)

{

	rb->__rb_parent_color |= RB_BLACK;

	rb->__rb_parent_color += RB_BLACK;

}



static inline struct rb_node *rb_red_parent(struct rb_node *red)