source: xtideuniversalbios/trunk/Assembly_Library/Inc/Emulate.inc@ 120

; Project name  :   Emulation library
; Description   :   Macros for emulating later x86 instruction with older
;                   processors.
;                   Macros are used so optimized builds could be done
;                   easily for different processors.
;
;                   This file must be first to be included to
;                   any source file.
%ifndef EMULATE_INC
%define EMULATE_INC

; Defines for processor support. Unsupported instructions will be
; emulated using macros.
; If using 286, define USE_186 and USE_286
; If using 386, define USE_186, USE_286 and USE_386
; If AT class PC is used (instead of XT), define USE_AT
;%define USE_186                ; Define to use 18x/V20/V30 instructions
;%define USE_286                ; Define to use 286 instructions
;%define USE_386                ; Define to use 386 instructions
;%define USE_AT                 ; Define for AT class machine
; Above defines should be set on makefile!

CPU 8086                        ; Allow 8088/8086 instructions only
%ifdef USE_186
CPU 186                         ; Allow instructions up to 188/186/V20/V30
%elifdef USE_286
CPU 286                         ; Allow instructions up to 286
%elifdef USE_386
CPU 386                         ; Allow instructions up to 386
%endif
BITS 16                         ; Set 16 bit code generation

; Alignments for jump targets.
; Following values are optimal for different processor types:
; 286 and 386SX         WORD (16-bit, 2 bytes)
; 386DX and 486         DWORD (32-bit, 4 bytes)
; Pentium and later     QWORD (64-bit, 8 bytes)
%ifdef USE_AT
    %ifdef USE_386
        JUMP_ALIGN      EQU     4
        WORD_ALIGN      EQU     2
    %else ; USE_286
        JUMP_ALIGN      EQU     2
        WORD_ALIGN      EQU     2
    %endif
%else ; XT
    JUMP_ALIGN      EQU     1
    WORD_ALIGN      EQU     1
%endif

;==========================================================================

;--------------------------------------------------------------------
; Emulates BSF (Bit Scan Forward) instruction when necessary.
; BSF is used to find index of least significant bit.
;
; eBSF
;   Parameters:
;       %1:     Destination WORD Register for bit index (not CX or same as %2!)
;       %2:     Source WORD operand where to search bit (not CX or same as %1!)
;   Returns:
;       %1:     Index of highest order bit from %2
;       ZF:     Set if %2 is zero
;               Cleared if %2 is non-zero
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eBSF 2
%ifndef USE_386
    push    cx
    cmp     WORD %2, BYTE 0     ; Source operand is zero?
    je      SHORT %%Return      ;  If so, return with ZF set

    ; Set destination to zero and load mask for bit 0
    xor     %1, %1
    mov     cx, 1

ALIGN JUMP_ALIGN
%%BitLoop:
    test    %2, cx              ; Bit set?
    jnz     SHORT %%Return      ;  If so, return with ZF cleared
    shl     cx, 1               ; Prepare to test next bit
    inc     %1                  ; Increment bit index
    jmp     SHORT %%BitLoop     ; Loop until bit found
%%Return:
    pop     cx
;-----------------------------------
%else
    bsf     %1, %2
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates BSR (Bit Scan Reverse) instruction when necessary.
; BSR is used to find index of most significant bit.
;
; eBSR
;   Parameters:
;       %1:     Destination WORD Register for bit index (not CX or same as %2!)
;       %2:     Source WORD operand where to search bit (not CX or same as %1!)
;   Returns:
;       %1:     Index of highest order bit from %2
;       ZF:     Set if %2 is zero
;               Cleared if %2 is non-zero
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eBSR 2
%ifndef USE_386
    push    cx
    cmp     WORD %2, BYTE 0     ; Source operand is zero?
    je      SHORT %%Return      ;  If so, return with ZF set

    ; Load mask for highest order bit
    mov     cx, 1<<15
    mov     %1, 15

ALIGN JUMP_ALIGN
%%BitLoop:
    test    %2, cx              ; Bit set?
    jnz     SHORT %%Return      ;  If so, return with ZF cleared
    shr     cx, 1               ; Prepare to test next bit
    dec     %1                  ; Decrement bit index
    jmp     SHORT %%BitLoop     ; Loop until bit found
%%Return:
    pop     cx
;-----------------------------------
%else
    bsr     %1, %2
%endif
%endmacro


;--------------------------------------------------------------------
; Conditional Move.
;
; eCMOVcc
;   Parameters:
;       %1:     Destination data
;       %2:     Source data
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eCMOVC 2
    jnc     SHORT %%Return
    mov     %1, %2
%%Return:
%endmacro

%macro eCMOVZ 2
    jnz     SHORT %%Return
    mov     %1, %2
%%Return:
%endmacro

%macro eCMOVNZ 2
    jz      SHORT %%Return
    mov     %1, %2
%%Return:
%endmacro

%macro eCMOVE 2
    eCMOVZ %1, %2
%endmacro

%macro eCMOVNE 2
    eCMOVNZ %1, %2
%endmacro

%macro eCMOVB 2
    jnb     SHORT %%Return
    mov     %1, %2
%%Return:
%endmacro



;--------------------------------------------------------------------
; Moves byte with zero-extending to any Register.
;
; eMOVZX
;   Parameters:
;       %1:     Destination Register (SP not supported)
;       %2:     Byte register or byte address
;   Returns:
;       Nothing
;   Corrupts registers:
;       FLAGS
;--------------------------------------------------------------------
%macro eMOVZX 2
%ifndef USE_386
    %ifidni %1, ax
        mov     al, %2
        xor     ah, ah
    %elifidni %1, bx
        mov     bl, %2
        xor     bh, bh      ; %2 may use BX in effective address
    %elifidni %1, cx
        mov     cl, %2
        xor     ch, ch
    %elifidni %1, dx
        mov     dl, %2
        xor     dh, dh
    %else   ; SI, DI, BP (all may be used in effective address)
        push    ax
        mov     al, %2
        xor     ah, ah
        xchg    ax, %1
        pop     ax
    %endif
;-----------------------------------
%else
    movzx   %1, %2
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates PUSHA instruction when necessary.
;
; ePUSHA
;   Parameters:
;       Nothing
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro ePUSHA 0
%ifndef USE_186
    push    ax
    push    cx
    push    dx
    push    bx
    push    sp
    push    bp
    push    si
    push    di
;-----------------------------------
%else
    pusha
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates POPA instruction when necessary.
;
; ePOPA
;   Parameters:
;       Nothing
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro ePOPA 0
%ifndef USE_186
    pop     di
    pop     si
    pop     bp
    pop     ax      ; Skip SP
    pop     bx
    pop     dx
    pop     cx
    pop     ax
;-----------------------------------
%else
    popa
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates ENTER instruction when necessary.
;
; eENTER
;   Parameters:
;       %1:     Number of bytes to reserve from stack
;       %2:     The lexical nesting level (not emulated, set to 0)
;   Returns:
;       SS:BP:  Ptr to old BP
;               ([bp-2] points to highest local stack frame word)
;   Corrupts registers:
;       FLAGS
;--------------------------------------------------------------------
%macro eENTER 2
%ifndef USE_186
    push    bp
    mov     bp, sp
    sub     sp, %1
;-----------------------------------
%else
    enter   %1, %2
%endif
%endmacro

;--------------------------------------------------------------------
; Emulates LEAVE instruction when necessary.
;
; eLEAVE
;   Parameters:
;       Nothing
;   Returns:
;       BP:     What it was before eENTER
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eLEAVE 0
%ifndef USE_186
    mov     sp, bp
    pop     bp
;-----------------------------------
%else
    leave
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates LSS instruction when necessary.
;
; eLSS
;   Parameters:
;       %1:     Destination register
;       %2:     Source memory address without brackets
;   Returns:
;       IF:     0 (interrupts disabled)
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eLSS 2
%ifndef USE_386
    cli                         ; Disable interrupts
    mov     %1, [%2]            ; Load offset
    mov     ss, [%2+2]          ; Load segment
;-----------------------------------
%else
    lss     %1, [%2]
%endif
%endmacro


;--------------------------------------------------------------------
; Segment override prefix instruction.
;
; eSEG
;   Parameters:
;       %1:     Name of the segment (ES, CS, SS, DS, FS or GS)
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eSEG 1
    %ifidni %1, es
        db  00100110b
    %elifidni %1, cs
        db  00101110b
    %elifidni %1, ss
        db  00110110b
    %elifidni %1, ds
        db  00111110b
    %elifidni %1, fs
        db  01100100b
    %elifidni %1, gs
        db  01100101b
    %else
        %error "Invalid segment overried passed to eSEG!"
    %endif
%endmacro


;--------------------------------------------------------------------
; Repeats string instruction with segment override.
; This macro prevents 8088/8086 restart bug.
;
; eSEG_STR
;   Parameters:
;       %1:     REP/REPNE or REPE prefix
;       %2:     Source segment override (destination is always ES)
;       %3:     String instruction
;       CX:     Repeat count
;   Returns:
;       FLAGS for cmps and scas only
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eSEG_STR 3
%ifndef USE_186 ; 8088/8086 has string instruction restart bug when more than one prefix
     %%Loop:
        %1                      ; REP is the prefix that can be lost
        eSEG    %2              ; SEG is the prefix that won't be lost
        %3                      ; String instruction
        jcxz    %%End           ; Jump to end if no repeats left (preserves FLAGS)
        jmp     SHORT %%Loop    ; Loop while repeats left
     %%End:
%else   ; No bug on V20/V30 and later, don't know about 188/186
    eSEG    %2
    %1      %3
%endif
%endmacro


;--------------------------------------------------------------------
; Bit shifts and rotates with immediate.
;
; eSHIFT_IM
;   Parameters:
;       %1:     Shift target
;       %2:     Number of bits to shift
;       %3:     Instruction (SHL, SHR, ROL, ROR, RCL, RCR)
;   Returns:
;       FLAGS
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro eSHIFT_IM 3
%ifndef USE_186
    %ifidni %1, cl
        times %2    %3      %1, 1
    %elifidni %1, ch
        times %2    %3      %1, 1
    %elifidni %1, cx
        times %2    %3      %1, 1
    %else
        %if %2 > 7
            push    cx
            mov     cl, %2
            %3      %1, cl
            pop     cx
        %else
            times %2    %3      %1, 1
        %endif
    %endif
;-----------------------------------
%else
    %3      %1, %2
%endif
%endmacro
%macro eSHR_IM 2
    eSHIFT_IM   %1, %2, shr
%endmacro
%macro eSHL_IM 2
    eSHIFT_IM   %1, %2, shl
%endmacro
%macro eROR_IM 2
    eSHIFT_IM   %1, %2, ror
%endmacro
%macro eROL_IM 2
    eSHIFT_IM   %1, %2, rol
%endmacro
%macro eRCR_IM 2
    eSHIFT_IM   %1, %2, rcr
%endmacro
%macro eRCL_IM 2
    eSHIFT_IM   %1, %2, rcl
%endmacro


;--------------------------------------------------------------------
; Emulates PUSH imm instruction when necessary.
;
; ePUSH_I
;   Parameters:
;       %1:     Immediate to push
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
%macro ePUSH_I 1
%ifndef USE_186
    push    bp                  ; Immediate goes here
    push    bp
    mov     bp, sp
    mov     WORD [bp+2], %1
    pop     bp
;-----------------------------------
%else
    push    %1
%endif
%endmacro


;--------------------------------------------------------------------
; Emulates PUSH imm instruction when necessary.
; ePUSH_T uses temporary register for faster performance
; and smaller code size than ePUSH_I.
;
; ePUSH_T
;   Parameters:
;       %1:     Temporary Register
;       %2:     Immediate to push
;   Returns:
;       Nothing
;   Corrupts registers:
;       %1
;--------------------------------------------------------------------
%macro ePUSH_T 2
%ifndef USE_186
    %ifidni %2, 0
        xor     %1, %1
    %else
        mov     %1, %2
    %endif
    push    %1
;-----------------------------------
%else
    push    %2
%endif
%endmacro


%endif ; EMULATE_INC