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      1 ;
      2 ; jccolext.asm - colorspace conversion (MMX)
      3 ;
      4 ; Copyright 2009 Pierre Ossman <ossman (a] cendio.se> for Cendio AB
      5 ;
      6 ; Based on the x86 SIMD extension for IJG JPEG library
      7 ; Copyright (C) 1999-2006, MIYASAKA Masaru.
      8 ; For conditions of distribution and use, see copyright notice in jsimdext.inc
      9 ;
     10 ; This file should be assembled with NASM (Netwide Assembler),
     11 ; can *not* be assembled with Microsoft's MASM or any compatible
     12 ; assembler (including Borland's Turbo Assembler).
     13 ; NASM is available from http://nasm.sourceforge.net/ or
     14 ; http://sourceforge.net/project/showfiles.php?group_id=6208
     15 ;
     16 ; [TAB8]
     17 
     18 %include "jcolsamp.inc"
     19 
     20 ; --------------------------------------------------------------------------
     21 ;
     22 ; Convert some rows of samples to the output colorspace.
     23 ;
     24 ; GLOBAL(void)
     25 ; jsimd_rgb_ycc_convert_mmx (JDIMENSION img_width,
     26 ;                           JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
     27 ;                           JDIMENSION output_row, int num_rows);
     28 ;
     29 
     30 %define img_width(b)    (b)+8           ; JDIMENSION img_width
     31 %define input_buf(b)    (b)+12          ; JSAMPARRAY input_buf
     32 %define output_buf(b)   (b)+16          ; JSAMPIMAGE output_buf
     33 %define output_row(b)   (b)+20          ; JDIMENSION output_row
     34 %define num_rows(b)     (b)+24          ; int num_rows
     35 
     36 %define original_ebp    ebp+0
     37 %define wk(i)           ebp-(WK_NUM-(i))*SIZEOF_MMWORD  ; mmword wk[WK_NUM]
     38 %define WK_NUM          8
     39 %define gotptr          wk(0)-SIZEOF_POINTER    ; void * gotptr
     40 
     41         align   16
     42         global  EXTN(jsimd_rgb_ycc_convert_mmx)
     43 
     44 EXTN(jsimd_rgb_ycc_convert_mmx):
     45         push    ebp
     46         mov     eax,esp                         ; eax = original ebp
     47         sub     esp, byte 4
     48         and     esp, byte (-SIZEOF_MMWORD)      ; align to 64 bits
     49         mov     [esp],eax
     50         mov     ebp,esp                         ; ebp = aligned ebp
     51         lea     esp, [wk(0)]
     52         pushpic eax             ; make a room for GOT address
     53         push    ebx
     54 ;       push    ecx             ; need not be preserved
     55 ;       push    edx             ; need not be preserved
     56         push    esi
     57         push    edi
     58 
     59         get_GOT ebx                     ; get GOT address
     60         movpic  POINTER [gotptr], ebx   ; save GOT address
     61 
     62         mov     ecx, JDIMENSION [img_width(eax)]        ; num_cols
     63         test    ecx,ecx
     64         jz      near .return
     65 
     66         push    ecx
     67 
     68         mov     esi, JSAMPIMAGE [output_buf(eax)]
     69         mov     ecx, JDIMENSION [output_row(eax)]
     70         mov     edi, JSAMPARRAY [esi+0*SIZEOF_JSAMPARRAY]
     71         mov     ebx, JSAMPARRAY [esi+1*SIZEOF_JSAMPARRAY]
     72         mov     edx, JSAMPARRAY [esi+2*SIZEOF_JSAMPARRAY]
     73         lea     edi, [edi+ecx*SIZEOF_JSAMPROW]
     74         lea     ebx, [ebx+ecx*SIZEOF_JSAMPROW]
     75         lea     edx, [edx+ecx*SIZEOF_JSAMPROW]
     76 
     77         pop     ecx
     78 
     79         mov     esi, JSAMPARRAY [input_buf(eax)]
     80         mov     eax, INT [num_rows(eax)]
     81         test    eax,eax
     82         jle     near .return
     83         alignx  16,7
     84 .rowloop:
     85         pushpic eax
     86         push    edx
     87         push    ebx
     88         push    edi
     89         push    esi
     90         push    ecx                     ; col
     91 
     92         mov     esi, JSAMPROW [esi]     ; inptr
     93         mov     edi, JSAMPROW [edi]     ; outptr0
     94         mov     ebx, JSAMPROW [ebx]     ; outptr1
     95         mov     edx, JSAMPROW [edx]     ; outptr2
     96         movpic  eax, POINTER [gotptr]   ; load GOT address (eax)
     97 
     98         cmp     ecx, byte SIZEOF_MMWORD
     99         jae     short .columnloop
    100         alignx  16,7
    101 
    102 %if RGB_PIXELSIZE == 3 ; ---------------
    103 
    104 .column_ld1:
    105         push    eax
    106         push    edx
    107         lea     ecx,[ecx+ecx*2]         ; imul ecx,RGB_PIXELSIZE
    108         test    cl, SIZEOF_BYTE
    109         jz      short .column_ld2
    110         sub     ecx, byte SIZEOF_BYTE
    111         xor     eax,eax
    112         mov     al, BYTE [esi+ecx]
    113 .column_ld2:
    114         test    cl, SIZEOF_WORD
    115         jz      short .column_ld4
    116         sub     ecx, byte SIZEOF_WORD
    117         xor     edx,edx
    118         mov     dx, WORD [esi+ecx]
    119         shl     eax, WORD_BIT
    120         or      eax,edx
    121 .column_ld4:
    122         movd    mmA,eax
    123         pop     edx
    124         pop     eax
    125         test    cl, SIZEOF_DWORD
    126         jz      short .column_ld8
    127         sub     ecx, byte SIZEOF_DWORD
    128         movd    mmG, DWORD [esi+ecx]
    129         psllq   mmA, DWORD_BIT
    130         por     mmA,mmG
    131 .column_ld8:
    132         test    cl, SIZEOF_MMWORD
    133         jz      short .column_ld16
    134         movq    mmG,mmA
    135         movq    mmA, MMWORD [esi+0*SIZEOF_MMWORD]
    136         mov     ecx, SIZEOF_MMWORD
    137         jmp     short .rgb_ycc_cnv
    138 .column_ld16:
    139         test    cl, 2*SIZEOF_MMWORD
    140         mov     ecx, SIZEOF_MMWORD
    141         jz      short .rgb_ycc_cnv
    142         movq    mmF,mmA
    143         movq    mmA, MMWORD [esi+0*SIZEOF_MMWORD]
    144         movq    mmG, MMWORD [esi+1*SIZEOF_MMWORD]
    145         jmp     short .rgb_ycc_cnv
    146         alignx  16,7
    147 
    148 .columnloop:
    149         movq    mmA, MMWORD [esi+0*SIZEOF_MMWORD]
    150         movq    mmG, MMWORD [esi+1*SIZEOF_MMWORD]
    151         movq    mmF, MMWORD [esi+2*SIZEOF_MMWORD]
    152 
    153 .rgb_ycc_cnv:
    154         ; mmA=(00 10 20 01 11 21 02 12)
    155         ; mmG=(22 03 13 23 04 14 24 05)
    156         ; mmF=(15 25 06 16 26 07 17 27)
    157 
    158         movq      mmD,mmA
    159         psllq     mmA,4*BYTE_BIT        ; mmA=(-- -- -- -- 00 10 20 01)
    160         psrlq     mmD,4*BYTE_BIT        ; mmD=(11 21 02 12 -- -- -- --)
    161 
    162         punpckhbw mmA,mmG               ; mmA=(00 04 10 14 20 24 01 05)
    163         psllq     mmG,4*BYTE_BIT        ; mmG=(-- -- -- -- 22 03 13 23)
    164 
    165         punpcklbw mmD,mmF               ; mmD=(11 15 21 25 02 06 12 16)
    166         punpckhbw mmG,mmF               ; mmG=(22 26 03 07 13 17 23 27)
    167 
    168         movq      mmE,mmA
    169         psllq     mmA,4*BYTE_BIT        ; mmA=(-- -- -- -- 00 04 10 14)
    170         psrlq     mmE,4*BYTE_BIT        ; mmE=(20 24 01 05 -- -- -- --)
    171 
    172         punpckhbw mmA,mmD               ; mmA=(00 02 04 06 10 12 14 16)
    173         psllq     mmD,4*BYTE_BIT        ; mmD=(-- -- -- -- 11 15 21 25)
    174 
    175         punpcklbw mmE,mmG               ; mmE=(20 22 24 26 01 03 05 07)
    176         punpckhbw mmD,mmG               ; mmD=(11 13 15 17 21 23 25 27)
    177 
    178         pxor      mmH,mmH
    179 
    180         movq      mmC,mmA
    181         punpcklbw mmA,mmH               ; mmA=(00 02 04 06)
    182         punpckhbw mmC,mmH               ; mmC=(10 12 14 16)
    183 
    184         movq      mmB,mmE
    185         punpcklbw mmE,mmH               ; mmE=(20 22 24 26)
    186         punpckhbw mmB,mmH               ; mmB=(01 03 05 07)
    187 
    188         movq      mmF,mmD
    189         punpcklbw mmD,mmH               ; mmD=(11 13 15 17)
    190         punpckhbw mmF,mmH               ; mmF=(21 23 25 27)
    191 
    192 %else ; RGB_PIXELSIZE == 4 ; -----------
    193 
    194 .column_ld1:
    195         test    cl, SIZEOF_MMWORD/8
    196         jz      short .column_ld2
    197         sub     ecx, byte SIZEOF_MMWORD/8
    198         movd    mmA, DWORD [esi+ecx*RGB_PIXELSIZE]
    199 .column_ld2:
    200         test    cl, SIZEOF_MMWORD/4
    201         jz      short .column_ld4
    202         sub     ecx, byte SIZEOF_MMWORD/4
    203         movq    mmF,mmA
    204         movq    mmA, MMWORD [esi+ecx*RGB_PIXELSIZE]
    205 .column_ld4:
    206         test    cl, SIZEOF_MMWORD/2
    207         mov     ecx, SIZEOF_MMWORD
    208         jz      short .rgb_ycc_cnv
    209         movq    mmD,mmA
    210         movq    mmC,mmF
    211         movq    mmA, MMWORD [esi+0*SIZEOF_MMWORD]
    212         movq    mmF, MMWORD [esi+1*SIZEOF_MMWORD]
    213         jmp     short .rgb_ycc_cnv
    214         alignx  16,7
    215 
    216 .columnloop:
    217         movq    mmA, MMWORD [esi+0*SIZEOF_MMWORD]
    218         movq    mmF, MMWORD [esi+1*SIZEOF_MMWORD]
    219         movq    mmD, MMWORD [esi+2*SIZEOF_MMWORD]
    220         movq    mmC, MMWORD [esi+3*SIZEOF_MMWORD]
    221 
    222 .rgb_ycc_cnv:
    223         ; mmA=(00 10 20 30 01 11 21 31)
    224         ; mmF=(02 12 22 32 03 13 23 33)
    225         ; mmD=(04 14 24 34 05 15 25 35)
    226         ; mmC=(06 16 26 36 07 17 27 37)
    227 
    228         movq      mmB,mmA
    229         punpcklbw mmA,mmF               ; mmA=(00 02 10 12 20 22 30 32)
    230         punpckhbw mmB,mmF               ; mmB=(01 03 11 13 21 23 31 33)
    231 
    232         movq      mmG,mmD
    233         punpcklbw mmD,mmC               ; mmD=(04 06 14 16 24 26 34 36)
    234         punpckhbw mmG,mmC               ; mmG=(05 07 15 17 25 27 35 37)
    235 
    236         movq      mmE,mmA
    237         punpcklwd mmA,mmD               ; mmA=(00 02 04 06 10 12 14 16)
    238         punpckhwd mmE,mmD               ; mmE=(20 22 24 26 30 32 34 36)
    239 
    240         movq      mmH,mmB
    241         punpcklwd mmB,mmG               ; mmB=(01 03 05 07 11 13 15 17)
    242         punpckhwd mmH,mmG               ; mmH=(21 23 25 27 31 33 35 37)
    243 
    244         pxor      mmF,mmF
    245 
    246         movq      mmC,mmA
    247         punpcklbw mmA,mmF               ; mmA=(00 02 04 06)
    248         punpckhbw mmC,mmF               ; mmC=(10 12 14 16)
    249 
    250         movq      mmD,mmB
    251         punpcklbw mmB,mmF               ; mmB=(01 03 05 07)
    252         punpckhbw mmD,mmF               ; mmD=(11 13 15 17)
    253 
    254         movq      mmG,mmE
    255         punpcklbw mmE,mmF               ; mmE=(20 22 24 26)
    256         punpckhbw mmG,mmF               ; mmG=(30 32 34 36)
    257 
    258         punpcklbw mmF,mmH
    259         punpckhbw mmH,mmH
    260         psrlw     mmF,BYTE_BIT          ; mmF=(21 23 25 27)
    261         psrlw     mmH,BYTE_BIT          ; mmH=(31 33 35 37)
    262 
    263 %endif ; RGB_PIXELSIZE ; ---------------
    264 
    265         ; mm0=(R0 R2 R4 R6)=RE, mm2=(G0 G2 G4 G6)=GE, mm4=(B0 B2 B4 B6)=BE
    266         ; mm1=(R1 R3 R5 R7)=RO, mm3=(G1 G3 G5 G7)=GO, mm5=(B1 B3 B5 B7)=BO
    267 
    268         ; (Original)
    269         ; Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
    270         ; Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
    271         ; Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
    272         ;
    273         ; (This implementation)
    274         ; Y  =  0.29900 * R + 0.33700 * G + 0.11400 * B + 0.25000 * G
    275         ; Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
    276         ; Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
    277 
    278         movq      MMWORD [wk(0)], mm0   ; wk(0)=RE
    279         movq      MMWORD [wk(1)], mm1   ; wk(1)=RO
    280         movq      MMWORD [wk(2)], mm4   ; wk(2)=BE
    281         movq      MMWORD [wk(3)], mm5   ; wk(3)=BO
    282 
    283         movq      mm6,mm1
    284         punpcklwd mm1,mm3
    285         punpckhwd mm6,mm3
    286         movq      mm7,mm1
    287         movq      mm4,mm6
    288         pmaddwd   mm1,[GOTOFF(eax,PW_F0299_F0337)] ; mm1=ROL*FIX(0.299)+GOL*FIX(0.337)
    289         pmaddwd   mm6,[GOTOFF(eax,PW_F0299_F0337)] ; mm6=ROH*FIX(0.299)+GOH*FIX(0.337)
    290         pmaddwd   mm7,[GOTOFF(eax,PW_MF016_MF033)] ; mm7=ROL*-FIX(0.168)+GOL*-FIX(0.331)
    291         pmaddwd   mm4,[GOTOFF(eax,PW_MF016_MF033)] ; mm4=ROH*-FIX(0.168)+GOH*-FIX(0.331)
    292 
    293         movq      MMWORD [wk(4)], mm1   ; wk(4)=ROL*FIX(0.299)+GOL*FIX(0.337)
    294         movq      MMWORD [wk(5)], mm6   ; wk(5)=ROH*FIX(0.299)+GOH*FIX(0.337)
    295 
    296         pxor      mm1,mm1
    297         pxor      mm6,mm6
    298         punpcklwd mm1,mm5               ; mm1=BOL
    299         punpckhwd mm6,mm5               ; mm6=BOH
    300         psrld     mm1,1                 ; mm1=BOL*FIX(0.500)
    301         psrld     mm6,1                 ; mm6=BOH*FIX(0.500)
    302 
    303         movq      mm5,[GOTOFF(eax,PD_ONEHALFM1_CJ)] ; mm5=[PD_ONEHALFM1_CJ]
    304 
    305         paddd     mm7,mm1
    306         paddd     mm4,mm6
    307         paddd     mm7,mm5
    308         paddd     mm4,mm5
    309         psrld     mm7,SCALEBITS         ; mm7=CbOL
    310         psrld     mm4,SCALEBITS         ; mm4=CbOH
    311         packssdw  mm7,mm4               ; mm7=CbO
    312 
    313         movq      mm1, MMWORD [wk(2)]   ; mm1=BE
    314 
    315         movq      mm6,mm0
    316         punpcklwd mm0,mm2
    317         punpckhwd mm6,mm2
    318         movq      mm5,mm0
    319         movq      mm4,mm6
    320         pmaddwd   mm0,[GOTOFF(eax,PW_F0299_F0337)] ; mm0=REL*FIX(0.299)+GEL*FIX(0.337)
    321         pmaddwd   mm6,[GOTOFF(eax,PW_F0299_F0337)] ; mm6=REH*FIX(0.299)+GEH*FIX(0.337)
    322         pmaddwd   mm5,[GOTOFF(eax,PW_MF016_MF033)] ; mm5=REL*-FIX(0.168)+GEL*-FIX(0.331)
    323         pmaddwd   mm4,[GOTOFF(eax,PW_MF016_MF033)] ; mm4=REH*-FIX(0.168)+GEH*-FIX(0.331)
    324 
    325         movq      MMWORD [wk(6)], mm0   ; wk(6)=REL*FIX(0.299)+GEL*FIX(0.337)
    326         movq      MMWORD [wk(7)], mm6   ; wk(7)=REH*FIX(0.299)+GEH*FIX(0.337)
    327 
    328         pxor      mm0,mm0
    329         pxor      mm6,mm6
    330         punpcklwd mm0,mm1               ; mm0=BEL
    331         punpckhwd mm6,mm1               ; mm6=BEH
    332         psrld     mm0,1                 ; mm0=BEL*FIX(0.500)
    333         psrld     mm6,1                 ; mm6=BEH*FIX(0.500)
    334 
    335         movq      mm1,[GOTOFF(eax,PD_ONEHALFM1_CJ)] ; mm1=[PD_ONEHALFM1_CJ]
    336 
    337         paddd     mm5,mm0
    338         paddd     mm4,mm6
    339         paddd     mm5,mm1
    340         paddd     mm4,mm1
    341         psrld     mm5,SCALEBITS         ; mm5=CbEL
    342         psrld     mm4,SCALEBITS         ; mm4=CbEH
    343         packssdw  mm5,mm4               ; mm5=CbE
    344 
    345         psllw     mm7,BYTE_BIT
    346         por       mm5,mm7               ; mm5=Cb
    347         movq      MMWORD [ebx], mm5     ; Save Cb
    348 
    349         movq      mm0, MMWORD [wk(3)]   ; mm0=BO
    350         movq      mm6, MMWORD [wk(2)]   ; mm6=BE
    351         movq      mm1, MMWORD [wk(1)]   ; mm1=RO
    352 
    353         movq      mm4,mm0
    354         punpcklwd mm0,mm3
    355         punpckhwd mm4,mm3
    356         movq      mm7,mm0
    357         movq      mm5,mm4
    358         pmaddwd   mm0,[GOTOFF(eax,PW_F0114_F0250)] ; mm0=BOL*FIX(0.114)+GOL*FIX(0.250)
    359         pmaddwd   mm4,[GOTOFF(eax,PW_F0114_F0250)] ; mm4=BOH*FIX(0.114)+GOH*FIX(0.250)
    360         pmaddwd   mm7,[GOTOFF(eax,PW_MF008_MF041)] ; mm7=BOL*-FIX(0.081)+GOL*-FIX(0.418)
    361         pmaddwd   mm5,[GOTOFF(eax,PW_MF008_MF041)] ; mm5=BOH*-FIX(0.081)+GOH*-FIX(0.418)
    362 
    363         movq      mm3,[GOTOFF(eax,PD_ONEHALF)]  ; mm3=[PD_ONEHALF]
    364 
    365         paddd     mm0, MMWORD [wk(4)]
    366         paddd     mm4, MMWORD [wk(5)]
    367         paddd     mm0,mm3
    368         paddd     mm4,mm3
    369         psrld     mm0,SCALEBITS         ; mm0=YOL
    370         psrld     mm4,SCALEBITS         ; mm4=YOH
    371         packssdw  mm0,mm4               ; mm0=YO
    372 
    373         pxor      mm3,mm3
    374         pxor      mm4,mm4
    375         punpcklwd mm3,mm1               ; mm3=ROL
    376         punpckhwd mm4,mm1               ; mm4=ROH
    377         psrld     mm3,1                 ; mm3=ROL*FIX(0.500)
    378         psrld     mm4,1                 ; mm4=ROH*FIX(0.500)
    379 
    380         movq      mm1,[GOTOFF(eax,PD_ONEHALFM1_CJ)] ; mm1=[PD_ONEHALFM1_CJ]
    381 
    382         paddd     mm7,mm3
    383         paddd     mm5,mm4
    384         paddd     mm7,mm1
    385         paddd     mm5,mm1
    386         psrld     mm7,SCALEBITS         ; mm7=CrOL
    387         psrld     mm5,SCALEBITS         ; mm5=CrOH
    388         packssdw  mm7,mm5               ; mm7=CrO
    389 
    390         movq      mm3, MMWORD [wk(0)]   ; mm3=RE
    391 
    392         movq      mm4,mm6
    393         punpcklwd mm6,mm2
    394         punpckhwd mm4,mm2
    395         movq      mm1,mm6
    396         movq      mm5,mm4
    397         pmaddwd   mm6,[GOTOFF(eax,PW_F0114_F0250)] ; mm6=BEL*FIX(0.114)+GEL*FIX(0.250)
    398         pmaddwd   mm4,[GOTOFF(eax,PW_F0114_F0250)] ; mm4=BEH*FIX(0.114)+GEH*FIX(0.250)
    399         pmaddwd   mm1,[GOTOFF(eax,PW_MF008_MF041)] ; mm1=BEL*-FIX(0.081)+GEL*-FIX(0.418)
    400         pmaddwd   mm5,[GOTOFF(eax,PW_MF008_MF041)] ; mm5=BEH*-FIX(0.081)+GEH*-FIX(0.418)
    401 
    402         movq      mm2,[GOTOFF(eax,PD_ONEHALF)]  ; mm2=[PD_ONEHALF]
    403 
    404         paddd     mm6, MMWORD [wk(6)]
    405         paddd     mm4, MMWORD [wk(7)]
    406         paddd     mm6,mm2
    407         paddd     mm4,mm2
    408         psrld     mm6,SCALEBITS         ; mm6=YEL
    409         psrld     mm4,SCALEBITS         ; mm4=YEH
    410         packssdw  mm6,mm4               ; mm6=YE
    411 
    412         psllw     mm0,BYTE_BIT
    413         por       mm6,mm0               ; mm6=Y
    414         movq      MMWORD [edi], mm6     ; Save Y
    415 
    416         pxor      mm2,mm2
    417         pxor      mm4,mm4
    418         punpcklwd mm2,mm3               ; mm2=REL
    419         punpckhwd mm4,mm3               ; mm4=REH
    420         psrld     mm2,1                 ; mm2=REL*FIX(0.500)
    421         psrld     mm4,1                 ; mm4=REH*FIX(0.500)
    422 
    423         movq      mm0,[GOTOFF(eax,PD_ONEHALFM1_CJ)] ; mm0=[PD_ONEHALFM1_CJ]
    424 
    425         paddd     mm1,mm2
    426         paddd     mm5,mm4
    427         paddd     mm1,mm0
    428         paddd     mm5,mm0
    429         psrld     mm1,SCALEBITS         ; mm1=CrEL
    430         psrld     mm5,SCALEBITS         ; mm5=CrEH
    431         packssdw  mm1,mm5               ; mm1=CrE
    432 
    433         psllw     mm7,BYTE_BIT
    434         por       mm1,mm7               ; mm1=Cr
    435         movq      MMWORD [edx], mm1     ; Save Cr
    436 
    437         sub     ecx, byte SIZEOF_MMWORD
    438         add     esi, byte RGB_PIXELSIZE*SIZEOF_MMWORD   ; inptr
    439         add     edi, byte SIZEOF_MMWORD                 ; outptr0
    440         add     ebx, byte SIZEOF_MMWORD                 ; outptr1
    441         add     edx, byte SIZEOF_MMWORD                 ; outptr2
    442         cmp     ecx, byte SIZEOF_MMWORD
    443         jae     near .columnloop
    444         test    ecx,ecx
    445         jnz     near .column_ld1
    446 
    447         pop     ecx                     ; col
    448         pop     esi
    449         pop     edi
    450         pop     ebx
    451         pop     edx
    452         poppic  eax
    453 
    454         add     esi, byte SIZEOF_JSAMPROW       ; input_buf
    455         add     edi, byte SIZEOF_JSAMPROW
    456         add     ebx, byte SIZEOF_JSAMPROW
    457         add     edx, byte SIZEOF_JSAMPROW
    458         dec     eax                             ; num_rows
    459         jg      near .rowloop
    460 
    461         emms            ; empty MMX state
    462 
    463 .return:
    464         pop     edi
    465         pop     esi
    466 ;       pop     edx             ; need not be preserved
    467 ;       pop     ecx             ; need not be preserved
    468         pop     ebx
    469         mov     esp,ebp         ; esp <- aligned ebp
    470         pop     esp             ; esp <- original ebp
    471         pop     ebp
    472         ret
    473 
    474 ; For some reason, the OS X linker does not honor the request to align the
    475 ; segment unless we do this.
    476         align   16
    477