!!!Please add intrinsics module for DMD DRuntime!!!

[Walter Bright via Digitalmars-d]

On 11/22/2016 3:07 PM, Johan Engelen wrote:
> On Tuesday, 22 November 2016 at 22:57:22 UTC, Iain Buclaw wrote:
>> It's a compilers job is to detect code patterns and emit suitable instructions
>> for them. :-)
>
> None of the compilers detect the body code pattern.

That is correct as far as bsf/bsr are concerned. The trouble with detecting a 
coding pattern is there are an endless number of ways such can be coded, and the 
compiler cannot detect all of them. Worse, the only way you can tell if the 
compiler did detect it is to look at the assembler output.

Nevertheless, the compiler still does detect some patterns, like for rol() and 
ror(), and uses a built-in operator for them. So that people use the detectable 
patterns, use the rol() template in core.bitop. The reason the compiler attempts 
to detect them anyway is there's a ton of code out there that has specific code 
written for rol/ror, and it's unlikely that people will ever rewrite it to use 
the templates.

You'll find that C/C++ compilers behave similarly. Burt Regehr did a blog entry 
on that a while back.

The compiler will also detect common forms of little/big endian byte 
manipulation, again see Regehr. This is pretty much standard behavior for modern 
compilers.