tmap.nas

开源的nasm编译器源码,研究编译器原理很有帮且

;;
;;      - wrap around 256 instead of 127.
;;      this is needed because we have a higher texture for mouselook,
;;      we need at least 200 lines for the sky.
;;
;;      NOTE: the sky should never wrap, so it could use a faster method.
;;            for the moment, we'll still use a wrapping method...
;;
;;      IT S JUST A QUICK CUT N PASTE, WAS NOT OPTIMISED AS IT SHOULD BE !!!
;;
;;----------------------------------------------------------------------

cglobal R_DrawSkyColumn_8
;       align   16
R_DrawSkyColumn_8:
        push    ebp
        push    esi
        push    edi
        push    ebx
;;
;; dest = ylookup[dc_yl] + columnofs[dc_x];
;;
        mov     ebp,[dc_yl]
        mov     ebx,ebp
        mov     edi,[ylookup+ebx*4]
        mov     ebx,[dc_x]
        add     edi,[columnofs+ebx*4]   ;; edi = dest
;;
;; pixelcount = yh - yl + 1
;;
        mov     eax,[dc_yh]
        inc     eax
        sub     eax,ebp                 ;; pixel count
        mov     [pixelcount],eax        ;; save for final pixel
        jle     near    vskydone        ;; nothing to scale
;;
;; frac = dc_texturemid - (centery-dc_yl)*fracstep;
;;
        mov     ecx,[dc_iscale]        ;; fracstep
        mov     eax,[centery]
        sub     eax,ebp
        imul    eax,ecx
        mov     edx,[dc_texturemid]
        sub     edx,eax
        mov     ebx,edx
        shr     ebx,16                  ;; frac int.
        and     ebx,0xff
        shl     edx,16                  ;; y frac up
        mov     ebp,ecx
        shl     ebp,16                  ;; fracstep f. up
        shr     ecx,16                  ;; fracstep i. ->cl
        mov     esi,[dc_source]
;;
;; lets rock :) !
;;
        mov     eax,[pixelcount]
        mov     dh,al
        shr     eax,0x2
        mov     ch,al                   ;; quad count
        mov     eax,[dc_colormap]
        test    dh,0x3
        je      vskyquadloop
;;
;;  do un-even pixel
;;
        test    dh,0x1
        je      f2
        mov     al,[esi+ebx]            ;; prep un-even loops
        add     edx,ebp                 ;; ypos f += ystep f
        adc     bl,cl                   ;; ypos i += ystep i
        mov     dl,[eax]                ;; colormap texel
        mov     [edi],dl                ;; output pixel
p8:     add     edi,0x12345678
;;
;;  do two non-quad-aligned pixels
;;
f2:     test    dh,0x2
        je      skyf3

        mov     al,[esi+ebx]            ;; fetch source texel
        add     edx,ebp                 ;; ypos f += ystep f
        adc     bl,cl                   ;; ypos i += ystep i
        mov     dl,[eax]                ;; colormap texel
        mov     [edi],dl                ;; output pixel

        mov     al,[esi+ebx]            ;; fetch source texel
        add     edx,ebp                 ;; ypos f += ystep f
        adc     bl,cl                   ;; ypos i += ystep i
        mov     dl,[eax]                ;; colormap texel
p9:     add     edi,0x12345678
        mov     [edi],dl                ;; output pixel

pa:     add     edi,0x12345678
;;
;;  test if there was at least 4 pixels
;;
skyf3:  test    ch,0xff                 ;; test quad count
        je      vskydone
;;
;; 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
;;
align 4
vskyquadloop:
        mov     al,[esi+ebx]            ;; prep loop
        add     edx,ebp                 ;; ypos f += ystep f
        mov     dl,[eax]                ;; colormap texel
        adc     bl,cl                   ;; ypos i += ystep i
        mov     [edi],dl                ;; output pixel

        mov     al,[esi+ebx]            ;; fetch source texel
        add     edx,ebp
        adc     bl,cl
pb:     add     edi,0x12345678
        mov     dl,[eax]
        mov     [edi],dl

        mov     al,[esi+ebx]            ;; fetch source texel
        add     edx,ebp
        adc     bl,cl
pc:     add     edi,0x12345678
        mov     dl,[eax]
        mov     [edi],dl

        mov     al,[esi+ebx]            ;; fetch source texel
        add     edx,ebp
        adc     bl,cl
pd:     add     edi,0x12345678
        mov     dl,[eax]
        mov     [edi],dl

pe:     add     edi,0x12345678

        dec     ch
        jne     vskyquadloop
vskydone:
        pop     ebx
        pop     edi
        pop     esi
        pop     ebp
        ret


;;----------------------------------------------------------------------
;; R_DrawTranslucentColumn_8
;;
;; Vertical column texture drawer, with transparency. Replaces Doom2's
;; 'fuzz' effect, which was not so beautiful.
;; Transparency is always impressive in some way, don't know why...
;;----------------------------------------------------------------------

cglobal R_DrawTranslucentColumn_8
R_DrawTranslucentColumn_8:
        push    ebp                     ;; preserve caller's stack frame pointer
        push    esi                     ;; preserve register variables
        push    edi
        push    ebx
;;
;; dest = ylookup[dc_yl] + columnofs[dc_x];
;;
        mov     ebp,[dc_yl]
        mov     ebx,ebp
        mov     edi,[ylookup+ebx*4]
        mov     ebx,[dc_x]
        add     edi,[columnofs+ebx*4]   ;; edi = dest
;;
;; pixelcount = yh - yl + 1
;;
        mov     eax,[dc_yh]
        inc     eax
        sub     eax,ebp                 ;; pixel count
        mov     [pixelcount],eax        ;; save for final pixel
        jle     near    vtdone         ;; nothing to scale
;;
;; frac = dc_texturemid - (centery-dc_yl)*fracstep;
;;
        mov     ecx,[dc_iscale]        ;; fracstep
        mov     eax,[centery]
        sub     eax,ebp
        imul    eax,ecx
        mov     edx,[dc_texturemid]
        sub     edx,eax
        mov     ebx,edx

        shr     ebx,16                  ;; frac int.
        and     ebx,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
        push    cx
        mov     ecx,edx
        pop     cx
        mov     edx,[dc_colormap]
        mov     esi,[dc_source]
;;
;; lets rock :) !
;;
        mov     eax,[pixelcount]
        shr     eax,0x2
        test    byte [pixelcount],0x3
        mov     ch,al                   ;; quad count
        mov     eax,[dc_transmap]
        je      vt4quadloop
;;
;;  do un-even pixel
;;
        test    byte [pixelcount],0x1
        je      trf2

        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        add     ecx,ebp
        adc     bl,cl
        mov     al,[edi]                ;; fetch dest  : index into colormap
        and     bl,0x7f
        mov     dl,[eax]
        mov     dl,[edx]
        mov     [edi],dl
pf:     add     edi,0x12345678
;;
;;  do two non-quad-aligned pixels
;;
trf2:    test    byte [pixelcount],0x2
        je      trf3

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

        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        add     ecx,ebp
        adc     bl,cl
        mov     al,[edi]                ;; fetch dest  : index into colormap
        and     bl,0x7f
        mov     dl,[eax]
        mov     dl,[edx]
        mov     [edi],dl
ph:     add     edi,0x12345678
;;
;;  test if there was at least 4 pixels
;;
trf3:   test    ch,0xff                 ;; test quad count
        je near vtdone

;;
;; 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
;;
vt4quadloop:
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     [tystep],ebp
pi:     add     edi,0x12345678
        mov     al,[edi]                ;; fetch dest  : index into colormap
pj:     sub     edi,0x12345678
        mov     ebp,edi
pk:     sub     edi,0x12345678
        jmp short inloop
align 4
vtquadloop:
        add     ecx,[tystep]
        adc     bl,cl
q1:     add     ebp,0x23456789
        and     bl,0x7f
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     dl,[edx]
        mov     [edi],dl
        mov     al,[ebp]                ;; fetch dest   : index into colormap
inloop:
        add     ecx,[tystep]
        adc     bl,cl
q2:     add     edi,0x23456789
        and     bl,0x7f
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     dl,[edx]
        mov     [ebp+0x0],dl
        mov     al,[edi]                ;; fetch dest   : index into colormap

        add     ecx,[tystep]
        adc     bl,cl
q3:     add     ebp,0x23456789
        and     bl,0x7f
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     dl,[edx]
        mov     [edi],dl
        mov     al,[ebp]                ;; fetch dest   : index into colormap

        add     ecx,[tystep]
        adc     bl,cl
q4:     add     edi,0x23456789
        and     bl,0x7f
        mov     dl,[eax]
        mov     ah,[esi+ebx]            ;; fetch texel : colormap number
        mov     dl,[edx]
        mov     [ebp],dl
        mov     al,[edi]                ;; fetch dest   : index into colormap

        dec     ch
        jne     vtquadloop
vtdone:
        pop     ebx
        pop     edi
        pop     esi
        pop     ebp
        ret


;;----------------------------------------------------------------------
;; R_DrawShadeColumn
;;
;;   for smoke..etc.. test.
;;----------------------------------------------------------------------
cglobal R_DrawShadeColumn_8
R_DrawShadeColumn_8:
        push    ebp                     ;; preserve caller's stack frame pointer
        push    esi                     ;; preserve register variables
        push    edi
        push    ebx

;;
;; dest = ylookup[dc_yl] + columnofs[dc_x];
;;
        mov     ebp,[dc_yl]
        mov     ebx,ebp
        mov     edi,[ylookup+ebx*4]
        mov     ebx,[dc_x]
        add     edi,[columnofs+ebx*4]  ;; edi = dest
;;
;; pixelcount = yh - yl + 1
;;
        mov     eax,[dc_yh]
        inc     eax
        sub     eax,ebp                 ;; pixel count
        mov     [pixelcount],eax       ;; save for final pixel
        jle near shdone                ;; nothing to scale
;;
;; frac = dc_texturemid - (centery-dc_yl)*fracstep;
;;
        mov     ecx,[dc_iscale]        ;; fracstep
        mov     eax,[centery]
        sub     eax,ebp
        imul    eax,ecx
        mov     edx,[dc_texturemid]