Test piece for different argument passing

[Steve Hutchesson]

This is simply a test piece using a similar argument passing technique to Win64. Data is written below the address in ESP and read by the called procedure. By not modifying the stack pointer, there is no need to balance the stack on procedure exit and the only overhead is the call - ret pair.

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 FUNCTION PBmain as LONG

    #REGISTER NONE

    LOCAL pa as DWORD
    LOCAL pb as DWORD

    a$ = "12345678901234567890"
    b$ = "                    "

    pa = StrPtr(a$)
    pb = StrPtr(b$)

    PREFIX "!"

    mov eax, pa
    mov edx, pb

    mov DWORD PTR [esp-8], eax              ' source address
    mov DWORD PTR [esp-12], edx             ' destination address
    mov DWORD PTR [esp-16], 20              ' byte count
    call fastcopy

    END PREFIX

    StdOut b$

    waitkey$

 End FUNCTION

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FASTPROC fastcopy

    PREFIX "!"

    mov edx, esi                            ' save esi
    mov eax, edi                            ' save edi

    mov esi, [esp-4]                        ' the call mnemonic reduces
    mov edi, [esp-8]                        ' stack memory address by 4
    mov ecx, [esp-12]
    rep movsb

    mov esi, edx                            ' restore esi
    mov edi, eax                            ' restore edi

    ret                                     ' ret with no stack correction

    END PREFIX

END FASTPROC

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