[fpc-pascal]Default calling convention

[Marcel Martin]

Florian Klaempfl a écrit :
> 
> Marcel Martin wrote:
> 
> > Florian Klaempfl a écrit :
> >
> >>Thomas Schatzl wrote:
> >>
> >>>In this case
> >>>
> >>>  procedure nx_fill(P: PLongword; Count: Longint; Value: Longword);
> >>>  assembler;
> >>>  asm
> >>>          pushl   %edi
> >>>          movl    P,%edi  // edi <- P
> >>>          movl    Value,%eax  // eax <- Value
> >>>          movl    Count,%ecx  // ecx <- Count
> >>>          rep
> >>>          stosl
> >>>          popl    %edi
> >>>  end;
> >>>
> >>>works both as embedded and non-embedded assembler procedure because the
> >>>order of assignments is ok in both cases.
> >>>
> >>>Btw, there's already a method in the system unit which does the same
> >>>thing as your routine: filldword()...
> >>
> >>... and with better instruction selection ;)
> >
> >
> > 1) This little routine was sent to point out a problem.
> >
> > 2) Better than what? Where do you see an "instruction selection"
> 
> Push instead of mov. mov is faster on modern machines because it causes
> less instruction dependencies.

1) That's what you call an 'instruction selection'? Such an answer 
is what I call bad faith. You were talking about checking the 
possible negativity of 'Count'.

2) Not with Delphi 5.01. With such a procedure, Delphi 5.01 doesn't 
generate the instructions "push ebp, etc. ". By using a local, you
constraint it to do that. In short, if you want to use 2 mov's
instead of push/pop by creating a local, you will have 2 mov's AND
a push/pop. Now I agree, this is no more true with FPC 1.9.4 since 
it seems to generate the sequence "push ebp ..." as soon as there 
is a parameter (even if there is no local and if this parameter is 
sent through a register). But you know what? My library was written 
with (and for) Delphi 5.01 and, I am sorry, but adapting 30,000 
lines of code for a compiler I don't know well cannot be done in 
two weeks. At least, _I_ cannot.

3) Next time I will have a problem with FPC, I will think twice
before talking about it on this list.

-- 
mm
http://www.ellipsa.net/