+ lib-rbtree-use-instead-of-for-setting-color.patch added to mm-nonmm-unstable branch

+ lib-rbtree-use-instead-of-for-setting-color.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: lib/rbtree: use '+' instead of '|' for setting color.
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     lib-rbtree-use-instead-of-for-setting-color.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-rbtree-use-instead-of-for-setting-color.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Noah Goldstein <goldstein.w.n@gmail.com>
Subject: lib/rbtree: use '+' instead of '|' for setting color.
Date: Tue, 4 Apr 2023 17:13:51 -0500

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 <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rbtree_augmented.h |    4 ++--
 lib/rbtree.c                     |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/include/linux/rbtree_augmented.h~lib-rbtree-use-instead-of-for-setting-color
+++ a/include/linux/rbtree_augmented.h
@@ -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
--- a/lib/rbtree.c~lib-rbtree-use-instead-of-for-setting-color
+++ a/lib/rbtree.c
@@ -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)
_

Patches currently in -mm which might be from goldstein.w.n@gmail.com are

lib-rbtree-use-instead-of-for-setting-color.patch