Re: [Xen-devel] [PATCH 02/20] lib/rbtree.c: optimize rb_erase()

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Sat, 2017-06-17 at 15:02 +0530, Praveen Kumar wrote:
> Tfour 4 redundant if-conditions in function __rb_erase_color() in
> lib/rbtree.c are removed.
> 
> In pseudo-source-code, the structure of the code is as follows:
> 
> if ((!A || B) && (!C || D)) {
> .
> .
> .
> } else {
>               if (!C || D) {//if this is true, it implies: (A ==
> true) && (B == false)
>                               if (A) {//hence this always evaluates
> to 'true'...
>                                               .
>                               }
>                               .
>                               //at this point, C always becomes true,
> because of:
>                               __rb_rotate_right/left();
>                               //and:
>                               other = parent->rb_right/left;
>               }
>               .
>               .
>               if (C) {//...and this too !
>                               .
>               }
> }
> 
> Signed-off-by: Wolfram Strepp <wstrepp@xxxxxx>
> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Cc: Andrea Arcangeli <andrea@xxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> [Linux commit 55a63998b8967615a15e2211ba0ff3a84a565824]
> 
> Ported to Xen.
> 
> Signed-off-by: Praveen Kumar <kpraveen.lkml@xxxxxxxxx>
>
Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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