tmap.nas

开源的nasm编译器源码,研究编译器原理很有帮且

        sub     edx,eax
        mov     ebx,edx
        shr     ebx,16                  ;; frac int.
        and     ebx,byte +0x7f
        shl     edx,16                  ;; y frac up

        mov     ebp,ecx
        shl     ebp,16                  ;; fracstep f. up
        shr     ecx,16                  ;; fracstep i. ->cl
        and     cl,0x7f

        mov     esi,[dc_source]
;;
;; lets rock :) !
;;
        mov     eax,[pixelcount]
        mov     dh,al
        shr     eax,2
        mov     ch,al                   ;; quad count
        mov     eax,[colormaps]
        test    dh,3
        je      sh4quadloop
;;
;;  do un-even pixel
;;
        test    dh,0x1
        je      shf2

        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        add     edx,ebp
        adc     bl,cl
        mov     al,[edi]                ;; fetch dest  : index into colormap
        and     bl,0x7f
        mov     dl,[eax]
        mov     [edi],dl
pl:     add     edi,0x12345678
;;
;;  do two non-quad-aligned pixels
;;
shf2:
        test    dh,0x2
        je      shf3

        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        add     edx,ebp
        adc     bl,cl
        mov     al,[edi]                ;; fetch dest  : index into colormap
        and     bl,0x7f
        mov     dl,[eax]
        mov     [edi],dl
pm:     add     edi,0x12345678

        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        add     edx,ebp
        adc     bl,cl
        mov     al,[edi]                ;; fetch dest  : index into colormap
        and     bl,0x7f
        mov     dl,[eax]
        mov     [edi],dl
pn:     add     edi,0x12345678
;;
;;  test if there was at least 4 pixels
;;
shf3:
        test    ch,0xff                 ;; test quad count
        je near shdone

;;
;; ebp : ystep frac. upper 24 bits
;; edx : y     frac. upper 24 bits
;; ebx : y     i.    lower 7 bits,  masked for index
;; ecx : ch = counter, cl = y step i.
;; eax : colormap aligned 256
;; esi : source texture column
;; edi : dest screen
;;
sh4quadloop:
        mov     dh,0x7f                 ;; prep mask
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [tystep],ebp
po:     add     edi,0x12345678
        mov     al,[edi]                ;; fetch dest  : index into colormap
pp:     sub     edi,0x12345678
        mov     ebp,edi
pq:     sub     edi,0x12345678
        jmp short shinloop

align  4
shquadloop:
        add     edx,[tystep]
        adc     bl,cl
        and     bl,dh
q5:     add     ebp,0x12345678
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [edi],dl
        mov     al,[ebp]                ;; fetch dest : index into colormap
shinloop:
        add     edx,[tystep]
        adc     bl,cl
        and     bl,dh
q6:     add     edi,0x12345678
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [ebp],dl
        mov     al,[edi]                ;; fetch dest : index into colormap

        add     edx,[tystep]
        adc     bl,cl
        and     bl,dh
q7:     add     ebp,0x12345678
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [edi],dl
        mov     al,[ebp]                ;; fetch dest : index into colormap

        add     edx,[tystep]
        adc     bl,cl
        and     bl,dh
q8:     add     edi,0x12345678
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [ebp],dl
        mov     al,[edi]                ;; fetch dest : index into colormap

        dec     ch
        jne     shquadloop

shdone:
        pop     ebx                     ;; restore register variables
        pop     edi
        pop     esi
        pop     ebp                     ;; restore caller's stack frame pointer
        ret



;;----------------------------------------------------------------------
;;
;;      R_DrawSpan
;;
;;      Horizontal texture mapping
;;
;;----------------------------------------------------------------------


[SECTION .data]

oldcolormap     dd      0

[SECTION CODE_SEG write]

cglobal R_DrawSpan_8
R_DrawSpan_8:
        push    ebp                     ;; preserve caller's stack frame pointer
        push    esi                     ;; preserve register variables
        push    edi
        push    ebx
;;
;; initilise registers
;;
  
        mov     edx, [ds_xfrac]
        mov     eax, [ds_ystep]
        ror     edx, 14
        ror     eax, 15
        mov      bl, dl
        mov     ecx, [ds_xstep]
        mov      dh, al
        mov      ax, 1
        mov     [tystep], eax


        mov     eax, [ds_yfrac]
        ror     ecx, 13
        ror     eax, 16
        mov      dl, cl
        mov      bh, al
        xor      cx, cx
        and     ebx, 0x3fff
        mov     [pixelcount],ecx

        mov     ecx, [ds_x2]
        mov     edi, [ds_y]
        mov     esi, [ds_x1]
        mov     edi, [ylookup+edi*4]
        mov     ebp, ebx
        add     edi, [columnofs+esi*4]
        sub     esi, ecx                ;; pixel count
        shr     ebp, 2
        mov     ecx, [ds_colormap]
        mov      ax, si
        mov     esi, [ds_source]
        sar      ax,1
        jnc     near .midloop           ;; check parity

;   summary
; edx = high16bit xfrac[0..13], ah=ystep[16..24] al=xtep[14..21]
; ebx = high16bit =0, bh=yfrac[16..24], bl=xfrac[14..21] 
; ecx = colormap table cl=0 (colormap is aligned 8 bits)
; eax = high16bit yfrac[0..15], dx = count
; esi = flat texture source
; edi = screeen buffer destination
; ebp = work register
; pixelcount = high16bit xstep[0..13] rest to 0
; tystep     = high16bit ystep[0..15] low 16 bit = 2 (increment of count)

align 4
.loop
        add     eax, [tystep]
         mov      cl, [esi+ebp]
        adc      bh, dh
         mov      cl, [ecx]
        and      bh, 0x3f 
         mov   [edi], cl
        mov     ebp, ebx        
         inc     edi
         shr     ebp, 2

.midloop:
        add     edx, [pixelcount]
         mov      cl, [esi+ebp]
        adc      bl, dl
         mov      cl, [ecx]
        mov     ebp, ebx 
         mov   [edi], cl
        inc     edi
         shr     ebp, 2

        test    eax, 0xffff
        jnz     near .loop

.hdone: pop     ebx                     ;; restore register variables
        pop     edi
        pop     esi
        pop     ebp                     ;; restore caller's stack frame pointer
        ret


[SECTION .data]

obelix          dd      0
etaussi         dd      0

[SECTION CODE_SEG]

cglobal R_DrawSpan_8_old
R_DrawSpan_8_old:
        push    ebp                     ;; preserve caller's stack frame pointer
        push    esi                     ;; preserve register variables
        push    edi
        push    ebx
;;
;; find loop count
;;
        mov     eax,[ds_x2]
        inc     eax
        sub     eax,[ds_x1]             ;; pixel count
        mov     [pixelcount],eax        ;; save for final pixel
        js near .hdone                  ;; nothing to scale
        shr     eax,0x1                 ;; double pixel count
        mov     [loopcount],eax
;;
;; build composite position
;;
        mov     ebp,[ds_xfrac]
        shl     ebp,10
        and     ebp,0xffff0000
        mov     eax,[ds_yfrac]
        shr     eax,6
        and     eax,0xffff
        mov     edi,[ds_y]
        or      ebp,eax

        mov     esi,[ds_source]
;;
;; calculate screen dest
;;
        mov     edi,[ylookup+edi*4]
        mov     eax,[ds_x1]
        add     edi,[columnofs+eax*4]
;;
;; build composite step
;;
        mov     ebx,[ds_xstep]
        shl     ebx,10
        and     ebx,0xffff0000
        mov     eax,[ds_ystep]
        shr     eax,6
        and     eax,0xffff
        or      ebx,eax

        mov     [obelix],ebx
        mov     [etaussi],esi

;; %eax      aligned colormap
;; %ebx      aligned colormap
;; %ecx,%edx  scratch
;; %esi      virtual source
;; %edi      moving destination pointer
;; %ebp      frac

        mov     eax,[ds_colormap]
        mov     ecx,ebp
        add     ebp,ebx                 ;; advance frac pointer
        shr     cx,10
        rol     ecx,6
        and     ecx,4095                ;; finish calculation for third pixel
        mov     edx,ebp
        shr     dx,10
        rol     edx,6
        add     ebp,ebx                 ;; advance frac pointer
        and     edx,4095                ;; finish calculation for fourth pixel
        mov     ebx,eax
        mov     al,[esi+ecx]            ;; get first pixel
        mov     bl,[esi+edx]            ;; get second pixel

        test dword [pixelcount],0xfffffffe

        mov     dl,[eax]                ;; color translate first pixel

;;      movw    $0xf0f0,%dx             ;;see visplanes start

        je      .hchecklast

        mov     dh,[ebx]                ;; color translate second pixel
        mov     esi,[loopcount]
align 4
.hdoubleloop:
        mov     ecx,ebp
        shr     cx,10
        rol     ecx,6
         add     ebp,[obelix]            ;; advance frac pointer
        mov     [edi],dx                ;; write first pixel
         and     ecx,4095                ;; finish calculation for third pixel
        mov     edx,ebp
        shr     dx,10
        rol     edx,6
         add     ecx,[etaussi]
        and     edx,4095                ;; finish calculation for fourth pixel
         mov     al,[ecx]                ;; get third pixel
        add     ebp,[obelix]            ;; advance frac pointer
         add     edx,[etaussi]
        mov     bl,[edx]                ;; get fourth pixel
         mov     dl,[eax]                ;; color translate third pixel
        add     edi,byte +0x2           ;; advance to third pixel destination
         dec     esi                     ;; done with loop?
        mov     dh,[ebx]                ;; color translate fourth pixel
         jne     .hdoubleloop
;; check for final pixel
.hchecklast:
        test dword [pixelcount],0x1
        je      .hdone
        mov     [edi],dl                ;; write final pixel
.hdone: pop     ebx                     ;; restore register variables
        pop     edi
        pop     esi
        pop     ebp                     ;; restore caller's stack frame pointer
        ret


;; ========================================================================
;;  Rasterization des segments d'un polyg搉e textur