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  Keyword:   _fastcall
 
  Syntax:    _fastcall declarator
 
  Summary:   Specifies that the function uses a calling convention that
             passes arguments in registers rather than on the stack,
             resulting in faster code.
 
  See also:  _cdecl, _export, _fortran, _interrupt, _pascal, _saveregs
 
     The choice of registers depends on the type of arguments:
 
     Type                     Register Candidates
 
     char / unsigned char     AL, DL, BL
     int / unsigned int       AX, DX, BX
     long / unsigned long     DX:AX
     near pointer             BX, AX, DX
     far or huge pointer      ES:BX
 
     Arguments are allocated to suitable registers if available, and
     are pushed onto the stack otherwise. Structs, unions, and all
     floating-point types are always pushed onto the stack.
 
     Return values of four bytes or smaller, including structs and
     unions, are placed in the registers as follows:
 
     Size        Register
 
     1 byte      AL
     2 bytes     AX
     4 bytes     DX:AX
 
     Floating-point values are returned on the stack. To return structs
     or unions larger than four bytes, the calling program pushes a
     hidden last parameter, which is a near pointer to a buffer in
     which the value is to be returned. A far pointer to
     SS:hidden-param must be returned in DX:AX.
 
     The _fastcall calling convention cannot be used with functions
     having variable-length parameter lists, or functions having any of
     the following attributes: _cdecl, _export, _fortran, _interrupt,
     _pascal, _saveregs_.
                                    -♦-