* support loading longint in dx:ax when using the 'register' calling convention

  on i8086. This is compatible with Borland C++ 3.1's _fastcall. Note that
  passing parameters in multiple registers is not yet implemented, so using this
  will cause internal errors, but these will be fixed later (and the 'register'
  calling convention was never officially supported on i8086).

git-svn-id: trunk@38784 -

compiler/i8086/cpupara.pas

@@ -591,19 +591,41 @@ unit cpupara;
                     hp.paraloc[side].Alignment:=paraalign;
                     hp.paraloc[side].def:=paradef;
                     {
-                      EAX
-                      EDX
-                      ECX
+                      AX
+                      DX
+                      BX
                       Stack
                       Stack
 
-                      64bit values,floats,arrays and records are always
-                      on the stack.
+                      32/64bit values,far pointers,floats,arrays and records are
+                      always on the stack. The only exception is that Longints
+                      (but not far pointers) can be passed in DX:AX if these
+                      registers are unallocated.
 
                       In case of po_delphi_nested_cc, the parent frame pointer
                       is also always passed on the stack.
                     }
-                    if (parareg<=high(parasupregs)) and
+                    if (parareg=low(parasupregs)) and
+                       (paralen=4) and
+                       (hp.vardef.typ=orddef) then
+                      begin
+                        if pass=1 then
+                          begin
+                            paraloc:=hp.paraloc[side].add_location;
+                            paraloc^.size:=OS_16;
+                            paraloc^.def:=paradef;
+                            paraloc^.loc:=LOC_REGISTER;
+                            paraloc^.register:=newreg(R_INTREGISTER,parasupregs[parareg],R_SUBW);
+                            inc(parareg);
+                            paraloc:=hp.paraloc[side].add_location;
+                            paraloc^.size:=OS_16;
+                            paraloc^.def:=paradef;
+                            paraloc^.loc:=LOC_REGISTER;
+                            paraloc^.register:=newreg(R_INTREGISTER,parasupregs[parareg],R_SUBW);
+                            inc(parareg);
+                          end;
+                      end
+                    else if (parareg<=high(parasupregs)) and
                        (paralen<=sizeof(aint)) and
                        (not(hp.vardef.typ in [floatdef,recorddef,arraydef]) or
                         pushaddr or