Re: [PATCH GIT 0.6] make use of register variables & size_t

From: David A. Wheeler <dwheeler@dwheeler.com>
Date: Apr 25, 2005, 18:06 UTC
Message-ID: <426D319B.2040805@dwheeler.com>
In-Reply-To: <426CD703.5040009@exactcode.de>

Rene Rebe wrote:

Show 12 quoted lines

> Hi,
>
> Matthias-Christian Ott wrote:
>
>> The "git" didn't try store small variables, which aren't referenced, 
>> in the processor registers. It also didn't use the size_t type. I 
>> corrected a C++ style comment too.
>
>
> Well, modern compilers take register as a non-binding hint. Your 
> register storage specification for those loop counters will not make 
> any change. You have not looked into the resulting binary?

Indeed, register was ALWAYS a non-binding hint. Today, unless you have specific measurements showing that adding "register" at some point improves the performance for a (somewhat common) situation, you're better off NOT including "register" nowadays. Today's compilers are generally better at allocating registers than people-who-have-little-time. Premature optimization is the root of all kinds of evil...

> Also // is valid C99 ...

It's not, strictly speaking, okay on old pre-C99 compilers. But in practice, practically all C compilers from the last 10+ years have accepted // comments as a very popular extension. So using "//" is unlikely to be a portability problem, even on semi-old compilers.

--- David A. Wheeler