[PATCH 01/10] Add vectorized getenv for glibc use

[Ondřej Bílka]

On Thu, May 16, 2013 at 07:12:46PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
> 
> This adds a general "vectorized getenv" for glibc internal use.
> The motivation is to allow subsystems to access environment variables
> cheaply without having to rescan the environment completely.
> 

> +      if (__builtin_expect ((*current)[0] == 'G', 0)
> +	  && (*current)[1] == 'L' && (*current)[2] == 'I'
> +	  && (*current)[3] == 'B' && (*current)[4] == 'C'
> +	  && (*current)[5] == '_')
This pattern repeats few times. A memcmp(current,"GLIBC",5) is shorter.

However I found that we and gcc do not expand memcmp. It will be slower
as in current codebase. 
I will shortly post patch with header that expands memcmp. 
Remind me to replace occurences when it will be accepted.

Ondra