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─────C/C++ Language─────────────────────────────────────────────────────────
 
  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, __pascal, __fortran, __interrupt
 
     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      passed on the stack
 
     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 floating-point 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 with functions having any
     of the following attributes: __cdecl, __export, __fortran,
     __interrupt, __pascal, __saveregs.
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