[fpc-pascal]Default calling convention

[Marcel Martin]

Thomas Schatzl a écrit :
> 
> Hello,
> 
> >>>>I noticed that, with FPC 1.9.4, the (default) calling convention
> >>>>"register" depends on the fact that a routine is or is not embedded
> >>>>in an other routine.
> >>>>
> >>>>With "proc(A,B,C: Longint);", if "proc" is not embedded then
> >>>>eax = A, edx = B and ecx = C but if "proc" is embedded then edx = A,
> >>>>ecx = B and C is on the stack.
> >>>>
> >>>>Is this convention definitive or temporary? I am not sure it is
> >>>>definitive since it makes the code of assembler routines dependent
> >>>>on their status: embedded or not.
> 
> This is exactly the same as Delphi (7) behaves.

I don't know, I have Delphi 5.01.
 
> >>  procedure nx_fill(P: PLongword; Count: Longint; Value: Longword);
> >>  assembler;
> >>  asm
> >>          pushl   %edi
> >>          movl    %eax,%edi  // edi <- P
> >>          movl    %ecx,%eax  // eax <- Value
> >>          movl    %edx,%ecx  // ecx <- Count
> >>          rep
> >>          stosl
> >>          popl    %edi
> >>  end;
> 
> 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.
 
Yes, but this way a program becomes a mineland. You write this, a few 
weeks later, for some reason, you change the line order, and you waste 
time to find why, suddenly, your program crashes (and yet, assuming you
immediately activate the bug).

-- 
mm
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