Re: [PATCH] Input:evdev - Fix to avoid the execution of same instruction in every iteration of for loop.
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2015-05-20 19:36:51
Also in:
lkml
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2015-05-20 19:36:51
Also in:
lkml
Hi Shailendra, On Thu, May 21, 2015 at 12:35:46AM +0530, Shailendra Verma wrote:
Here in for loop the instruction "len / sizeof(compat_long_t)" is used as a terminating condition which is executing (being computed) in every iteration of for loop. Below is the armv7-a architecture assembly code with similar for loop having the same instruction in condition.Note that the instruction "lsr r3, r3, #2" i.e Logical Shift Right on behalf of "len / sizeof(compat_long_t)" is getting executed every time the loop iterates.
No, it is not. We compile kernel with -O2 and compiler is smart enough to optimize such constructs. Thanks. -- Dmitry