[fpc-pascal] rotating bits

Tomas Hajny XHajT03 at mbox.vol.cz
Thu May 25 10:39:21 CEST 2006

Florian Klaempfl wrote:
> Tomas Hajny wrote:
>> On 25 May 06, at 0:10, ϸňđ Ęîńŕđĺâńęčé ń mail.ru wrote:
>>>>> First parameter is in eax, second in edx (third one is ecx)
>>> TH> Yes, of course, sorry for confusion... :-( Anyway, loading of the
>>> first
>>> TH> parameter can be still skipped (and the stack frame is probably not
>>> useful
>>> TH> in this case either). So you'd get:
>>> TH> function brol(b: byte; c: byte): byte; assembler; nostackframe;
>>> TH> asm
>>> TH>   movb  %dl,%cl
>>> TH>   rolb  %cl,%al
>>> TH> end ['cl'];
>>> TH> Tomas
>>> 1. So, is there any problem with including this functions and bit
>>> checks
>>> (bt./bs. in intel assembler: writing (a and (1 shl i)) isn't great
>>> too)?
>> I guess there is no problem in including it. The
>> only questions from my point of view are:
>> 1) Are they useful in general, so that it would
>> make sense to include them either in FPC itself
>> (as opposed to some standalone unit)?
> - they must be available for all cpu platforms, so we need at least a
> generic implementation

Generic implementation in Pascal has already been provided in this thread
as well, so this isn't an issue.

> - for an efficient implementation, this needs a compiler patch so the
> compiler can really efficiently inline

Would this apply for the operator case too? Isn't it then similar to
shl/shr (which "just work" now as well - even without special inlining

Of course, this would only make sense if we're convinced about the general
usefulness of such operators.


More information about the fpc-pascal mailing list