Is int faster than byte/short?

[Sean Cavanaugh]

On 4/30/2011 10:34 AM, Mariusz Gliwiński wrote:
> Hello,
> I'm trying to learn high-performance real-time programming.
>
> One of my wonderings are:
> Should i use int/uint for all standard arithmetic operations or
> int/short/byte (depends on actual case)?
> I believe this question has following subquestions:
> * Arithmetic computations performance
> * Memory access time
>
> My actual compiler is DMD, but I'm interested in GDC as well.
>
> Lastly, one more question would be:
> Could someone recommend any books/resources for this kind of
> informations and tips that could be applied to D? I'd like to defer my
> own experiments with generated assembly and profiling, but i suppose
> people already published general rules that i could apply for my
> programming.
>
> Thanks,
> Mariusz Gliwiński

My experience with this pattern of thinking is to use the largest data 
type that makes sense, unless you have a profiler saying you need to do 
something different.  However, if you get being obsessive-compulsive 
about having 'the perfectly sized integer types' for the code, it is 
possible to fall into the trap of over-using unsigned types 'because the 
value can never be negative'.  Unsigned 8 and 16 bit values usually have 
a good reason to be unsigned, but when you start getting to 32 and 64 
bit values it makes a lot less sense most of the time.

When working with non-X86 platforms other problems are usually much more 
severe: More expensive thread synchronization primitives, lack of 
efficient variable bit bit-shifting (run-time determined number of bits 
shifted), non-existent branch prediction, or various floating point code 
promoting to emulated double precision code silently on hardware that 
can only do single precision floating point etc.