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

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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: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: Michel Lespinasse <michel@lespinasse.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Noah Goldstein
2023-04-04 17:13:51 -05:00
committed by Andrew Morton
parent 1be2edb25c
commit b0687c1119
2 changed files with 3 additions and 3 deletions
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2
lib/rbtree.c
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@@ -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)