Re: [PATCH] small update for strlen, strnlen, use less cpu instructions

From: Alexey Dobriyan
Date: Tue Jun 16 2015 - 07:41:43 EST


> Now strlen() increments a variable for each character it faces,
> hence it will consume more cycles.

It doesn't matter if there is a dependency in a loop:

Before:
520: 48 83 c0 01 add $0x1,%rax
524: 80 38 00 cmpb $0x0,(%rax)
527: 75 f7 jne 520

After:
500: 48 83 c0 01 add $0x1,%rax
504: 80 3c 07 00 cmpb $0x0,(%rdi,%rax,1)
508: 75 f6 jne 500
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