[PATCH] rbtree

[PATCH] rbtree

[Érsek László]

Hi all,

this patch tries to remove those checks for 0 from
linux-2.4.19/lib/rbtree.c which are (I think) superfluous.

Laszlo Ersek


--- linux-2.4.19/lib/rbtree.c	Sat Aug  3 02:39:46 2002
+++ linux/lib/rbtree.c	Sun Nov 24 22:59:38 2002
@@ -159,17 +159,16 @@
 				if (!other->rb_right ||
 				    other->rb_right->rb_color == RB_BLACK)
 				{
-					register rb_node_t * o_left;
-					if ((o_left = other->rb_left))
-						o_left->rb_color = RB_BLACK;
+					/* unneeded check-for-0 removed */
+					other->rb_left->rb_color = RB_BLACK;
 					other->rb_color = RB_RED;
 					__rb_rotate_right(other, root);
 					other = parent->rb_right;
 				}
 				other->rb_color = parent->rb_color;
 				parent->rb_color = RB_BLACK;
-				if (other->rb_right)
-					other->rb_right->rb_color = RB_BLACK;
+				/* unneeded check-for-0 removed */
+				other->rb_right->rb_color = RB_BLACK;
 				__rb_rotate_left(parent, root);
 				node = root->rb_node;
 				break;
@@ -199,17 +198,16 @@
 				if (!other->rb_left ||
 				    other->rb_left->rb_color == RB_BLACK)
 				{
-					register rb_node_t * o_right;
-					if ((o_right = other->rb_right))
-						o_right->rb_color = RB_BLACK;
+					/* unneeded check-for-0 removed */
+					other->rb_right->rb_color = RB_BLACK;
 					other->rb_color = RB_RED;
 					__rb_rotate_left(other, root);
 					other = parent->rb_left;
 				}
 				other->rb_color = parent->rb_color;
 				parent->rb_color = RB_BLACK;
-				if (other->rb_left)
-					other->rb_left->rb_color = RB_BLACK;
+				/* unneeded check-for-0 removed */
+				other->rb_left->rb_color = RB_BLACK;
 				__rb_rotate_right(parent, root);
 				node = root->rb_node;
 				break;

RE: [PATCH] rbtree

[Folkert van Heusden]

Not trying to be negative and also really wondering this: won't
the compiler produce the same code for:
if (!variable)
and
if (variable == 0)
?

-----Oorspronkelijk bericht-----
Van: linux-kernel-owner@vger.kernel.org
[mailto:linux-kernel-owner@vger.kernel.org]Namens Ersek Laszlo
Verzonden: zondag 24 november 2002 23:41
Aan: linux-kernel@vger.kernel.org
Onderwerp: [PATCH] rbtree


Hi all,

this patch tries to remove those checks for 0 from
linux-2.4.19/lib/rbtree.c which are (I think) superfluous.

Laszlo Ersek


--- linux-2.4.19/lib/rbtree.c	Sat Aug  3 02:39:46 2002
+++ linux/lib/rbtree.c	Sun Nov 24 22:59:38 2002
@@ -159,17 +159,16 @@
 				if (!other->rb_right ||
 				    other->rb_right->rb_color == RB_BLACK)
 				{
-					register rb_node_t * o_left;
-					if ((o_left = other->rb_left))
-						o_left->rb_color = RB_BLACK;
+					/* unneeded check-for-0 removed */
+					other->rb_left->rb_color = RB_BLACK;
...

Re: [PATCH] rbtree

[Mike Black]

Mine produces the same code either way:
int
main()
{
   int i=0;
   if (i==0) {
       i++;
   }
}

gcc --version
2.95.3
   .file   "t1.c"
   .version    "01.01"
gcc2_compiled.:
.text
   .align 4
.globl main
   .type    main,@function
main:
   pushl %ebp
   movl %esp,%ebp
   subl $24,%esp
   movl $0,-4(%ebp)
   cmpl $0,-4(%ebp)
   jne .L3
   incl -4(%ebp)
.L3:
.L2:
   movl %ebp,%esp
   popl %ebp
   ret
.Lfe1:
   .size    main,.Lfe1-main
   .ident  "GCC: (GNU) 2.95.3 20010315 (release)"


----- Original Message ----- 
From: "Folkert van Heusden" <folkert@vanheusden.com>
To: "'Ersek Laszlo'" <erseklaszlo@chello.hu>; <linux-kernel@vger.kernel.org>
Sent: Monday, November 25, 2002 4:01 PM
Subject: RE: [PATCH] rbtree


> Not trying to be negative and also really wondering this: won't
> the compiler produce the same code for:
> if (!variable)
> and
> if (variable == 0)
> ?
> 
> -----Oorspronkelijk bericht-----
> Van: linux-kernel-owner@vger.kernel.org
> [mailto:linux-kernel-owner@vger.kernel.org]Namens Ersek Laszlo
> Verzonden: zondag 24 november 2002 23:41
> Aan: linux-kernel@vger.kernel.org
> Onderwerp: [PATCH] rbtree
> 
> 
> Hi all,
> 
> this patch tries to remove those checks for 0 from
> linux-2.4.19/lib/rbtree.c which are (I think) superfluous.
> 
> Laszlo Ersek
> 
> 
> --- linux-2.4.19/lib/rbtree.c Sat Aug  3 02:39:46 2002
> +++ linux/lib/rbtree.c Sun Nov 24 22:59:38 2002
> @@ -159,17 +159,16 @@
>   if (!other->rb_right ||
>       other->rb_right->rb_color == RB_BLACK)
>   {
> - register rb_node_t * o_left;
> - if ((o_left = other->rb_left))
> - o_left->rb_color = RB_BLACK;
> + /* unneeded check-for-0 removed */
> + other->rb_left->rb_color = RB_BLACK;
> ...
> -
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