freepascal.compiler/compiler/i386/n386ic.pas

{
    $Id$
    Copyright (c) 1998-2000 by Kovacs Attila Zoltan

    Generate i386 assembly wrapper code interface implementor objects

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 ****************************************************************************
}
unit n386ic;

interface

uses
  aasm,
  symbase,symtype,symtable,symdef,symsym;

procedure cgintfwrapper(asmlist: paasmoutput; procdef: pprocdef; const labelname: string; ioffset: longint);

implementation

uses
  globtype, systems,
  cobjects, verbose, globals,
  symconst, types,
{$ifdef GDB}
  strings, gdb,
{$endif GDB}
  hcodegen, temp_gen,
  cpubase, cpuasm,
  cgai386, tgeni386;

{
possible calling conventions:
              default stdcall cdecl pascal popstack register saveregisters
default(0):      OK     OK    OK(1)  OK     OK(1)      OK          OK
virtual(2):      OK     OK    OK(3)  OK     OK(3)      OK          OK(4)

(0):
    set self parameter to correct value
    jmp mangledname

(1): The code is the following
     set self parameter to correct value
     call mangledname
     set self parameter to interface value

(2): The wrapper code use %eax to reach the virtual method address
     set self to correct value
     move self,%eax
     mov  0(%eax),%eax ; load vmt
     jmp  vmtoffs(%eax) ; method offs

(3): The wrapper code use %eax to reach the virtual method address
     set self to correct value
     move self,%eax
     mov  0(%eax),%eax ; load vmt
     jmp  vmtoffs(%eax) ; method offs
     set self parameter to interface value


(4): Virtual use eax to reach the method address so the following code be generated:
     set self to correct value
     push %ebx ; allocate space for function address
     push %eax
     mov  self,%eax
     mov  0(%eax),%eax ; load vmt
     mov  vmtoffs(%eax),eax ; method offs
     mov  %eax,4(%esp)
     pop  %eax
     ret  0; jmp the address

}

function getselfoffsetfromsp(procdef: pprocdef): longint;
begin
  if not assigned(procdef^.parast^.symindex^.first) then
    getselfoffsetfromsp:=4
  else
    if psym(procdef^.parast^.symindex^.first)^.typ=varsym then
      getselfoffsetfromsp:=pvarsym(procdef^.parast^.symindex^.first)^.address+4
    else
      Internalerror(2000061310);
end;


procedure cgintfwrapper(asmlist: paasmoutput; procdef: pprocdef; const labelname: string; ioffset: longint);
  procedure checkvirtual;
  begin
    if (procdef^.extnumber=-1) then
      Internalerror(200006139);
  end;

  procedure adjustselfvalue(ioffset: longint);
  begin
    { sub $ioffset,offset(%esp) }
    emit_const_ref(A_SUB,S_L,ioffset,new_reference(R_ESP,getselfoffsetfromsp(procdef)));
  end;

  procedure getselftoeax(offs: longint);
  begin
    { mov offset(%esp),%eax }
    emit_ref_reg(A_MOV,S_L,new_reference(R_ESP,getselfoffsetfromsp(procdef)),R_EAX);
  end;

  procedure loadvmttoeax;
  begin
    checkvirtual;
    { mov  0(%eax),%eax ; load vmt}
    emit_ref_reg(A_MOV,S_L,new_reference(R_EAX,0),R_EAX);
  end;

  procedure op_oneaxmethodaddr(op: TAsmOp);
  begin
    { call/jmp  vmtoffs(%eax) ; method offs }
    emit_ref(op,S_L,new_reference(R_EAX,procdef^._class^.vmtmethodoffset(procdef^.extnumber)));
  end;

  procedure loadmethodoffstoeax;
  begin
    { mov  vmtoffs(%eax),%eax ; method offs }
    emit_ref_reg(A_MOV,S_L,new_reference(R_EAX,procdef^._class^.vmtmethodoffset(procdef^.extnumber)),R_EAX);
  end;

var
  oldexprasmlist: paasmoutput;
begin
  if procdef^.proctypeoption<>potype_none then
    Internalerror(200006137);
  if not assigned(procdef^._class) or
     (procdef^.procoptions*[po_containsself, po_classmethod, po_staticmethod,
       po_methodpointer, po_interrupt, po_iocheck]<>[]) then
    Internalerror(200006138);

  oldexprasmlist:=exprasmlist;
  exprasmlist:=asmlist;

  exprasmlist^.concat(new(pai_symbol,initname(labelname,0)));

  { set param1 interface to self  }
  adjustselfvalue(ioffset);

  { case 1  or 2 }
  if (pocall_clearstack in procdef^.proccalloptions) then
    begin
      if po_virtualmethod in procdef^.procoptions then
        begin { case 2 }
          getselftoeax(0);
          loadvmttoeax;
          op_oneaxmethodaddr(A_CALL);
        end
      else { case 1 }
        begin
          emitcall(procdef^.mangledname);
        end;
      { restore param1 value self to interface }
      adjustselfvalue(-ioffset);
    end
  { case 3 }
  else if [po_virtualmethod,po_saveregisters]*procdef^.procoptions=[po_virtualmethod,po_saveregisters] then
    begin
      emit_reg(A_PUSH,S_L,R_EBX); { allocate space for address}
      emit_reg(A_PUSH,S_L,R_EAX);
      getselftoeax(8);
      loadvmttoeax;
      loadmethodoffstoeax;
      { mov %eax,4(%esp) }
      emit_reg_ref(A_MOV,S_L,R_EAX,new_reference(R_ESP,4));
      { pop  %eax }
      emit_reg(A_POP,S_L,R_EAX);
      { ret  ; jump to the address }
      emit_none(A_RET,S_L);
    end
  { case 4 }
  else if po_virtualmethod in procdef^.procoptions then
    begin
      getselftoeax(0);
      loadvmttoeax;
      op_oneaxmethodaddr(A_JMP);
    end
  { case 0 }
  else
    begin
      emitcall(procdef^.mangledname);
    end;
  exprasmlist:=oldexprasmlist;
end;

end.
{
  $Log$
  Revision 1.1  2000-11-04 14:25:23  florian
    + merged Attila's changes for interfaces, not tested yet

  Revision 1.1.2.2  2000/06/15 15:05:30  kaz
    * An minor bug fix

  Revision 1.1.2.1  2000/06/15 06:26:34  kaz
    * Initial version
}