Re: [boost] optimization of boost::end

From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2008-01-03 12:35:51

Neal Becker wrote:
> The common idiom is:
> 
> for (; i != boost::end (vector); ++i) ...
> 
> The compiler had damn well better realize that boost::end is a constant
> function that can be lifted from the loop, or performance can be severely
> impacted.

boost::end is not a constant function, because the vector can change.

However, boost::end(vector) is the same as vector._M_begin + 
vector._M_size (implementation specific names)
I wouldn't say one addition can severely impact performance.

I believe a lot of optimizers can optimize out that addition if the 
vector wasn't changed anyway.