1;
2; jquant.asm - sample data conversion and quantization (MMX)
3;
4; Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
5;
6; Based on
7; x86 SIMD extension for IJG JPEG library
8; Copyright (C) 1999-2006, MIYASAKA Masaru.
9; For conditions of distribution and use, see copyright notice in jsimdext.inc
10;
11; This file should be assembled with NASM (Netwide Assembler),
12; can *not* be assembled with Microsoft's MASM or any compatible
13; assembler (including Borland's Turbo Assembler).
14; NASM is available from http://nasm.sourceforge.net/ or
15; http://sourceforge.net/project/showfiles.php?group_id=6208
16;
17; [TAB8]
18
19%include "jsimdext.inc"
20%include "jdct.inc"
21
22; --------------------------------------------------------------------------
23        SECTION SEG_TEXT
24        BITS    32
25;
26; Load data into workspace, applying unsigned->signed conversion
27;
28; GLOBAL(void)
29; jsimd_convsamp_mmx (JSAMPARRAY sample_data, JDIMENSION start_col,
30;                     DCTELEM * workspace);
31;
32
33%define sample_data     ebp+8           ; JSAMPARRAY sample_data
34%define start_col       ebp+12          ; JDIMENSION start_col
35%define workspace       ebp+16          ; DCTELEM * workspace
36
37        align   16
38        global  EXTN(jsimd_convsamp_mmx)
39
40EXTN(jsimd_convsamp_mmx):
41        push    ebp
42        mov     ebp,esp
43        push    ebx
44;       push    ecx             ; need not be preserved
45;       push    edx             ; need not be preserved
46        push    esi
47        push    edi
48
49        pxor    mm6,mm6                 ; mm6=(all 0's)
50        pcmpeqw mm7,mm7
51        psllw   mm7,7                   ; mm7={0xFF80 0xFF80 0xFF80 0xFF80}
52
53        mov     esi, JSAMPARRAY [sample_data]   ; (JSAMPROW *)
54        mov     eax, JDIMENSION [start_col]
55        mov     edi, POINTER [workspace]        ; (DCTELEM *)
56        mov     ecx, DCTSIZE/4
57        alignx  16,7
58.convloop:
59        mov     ebx, JSAMPROW [esi+0*SIZEOF_JSAMPROW]   ; (JSAMPLE *)
60        mov     edx, JSAMPROW [esi+1*SIZEOF_JSAMPROW]   ; (JSAMPLE *)
61
62        movq    mm0, MMWORD [ebx+eax*SIZEOF_JSAMPLE]    ; mm0=(01234567)
63        movq    mm1, MMWORD [edx+eax*SIZEOF_JSAMPLE]    ; mm1=(89ABCDEF)
64
65        mov     ebx, JSAMPROW [esi+2*SIZEOF_JSAMPROW]   ; (JSAMPLE *)
66        mov     edx, JSAMPROW [esi+3*SIZEOF_JSAMPROW]   ; (JSAMPLE *)
67
68        movq    mm2, MMWORD [ebx+eax*SIZEOF_JSAMPLE]    ; mm2=(GHIJKLMN)
69        movq    mm3, MMWORD [edx+eax*SIZEOF_JSAMPLE]    ; mm3=(OPQRSTUV)
70
71        movq      mm4,mm0
72        punpcklbw mm0,mm6               ; mm0=(0123)
73        punpckhbw mm4,mm6               ; mm4=(4567)
74        movq      mm5,mm1
75        punpcklbw mm1,mm6               ; mm1=(89AB)
76        punpckhbw mm5,mm6               ; mm5=(CDEF)
77
78        paddw   mm0,mm7
79        paddw   mm4,mm7
80        paddw   mm1,mm7
81        paddw   mm5,mm7
82
83        movq    MMWORD [MMBLOCK(0,0,edi,SIZEOF_DCTELEM)], mm0
84        movq    MMWORD [MMBLOCK(0,1,edi,SIZEOF_DCTELEM)], mm4
85        movq    MMWORD [MMBLOCK(1,0,edi,SIZEOF_DCTELEM)], mm1
86        movq    MMWORD [MMBLOCK(1,1,edi,SIZEOF_DCTELEM)], mm5
87
88        movq      mm0,mm2
89        punpcklbw mm2,mm6               ; mm2=(GHIJ)
90        punpckhbw mm0,mm6               ; mm0=(KLMN)
91        movq      mm4,mm3
92        punpcklbw mm3,mm6               ; mm3=(OPQR)
93        punpckhbw mm4,mm6               ; mm4=(STUV)
94
95        paddw   mm2,mm7
96        paddw   mm0,mm7
97        paddw   mm3,mm7
98        paddw   mm4,mm7
99
100        movq    MMWORD [MMBLOCK(2,0,edi,SIZEOF_DCTELEM)], mm2
101        movq    MMWORD [MMBLOCK(2,1,edi,SIZEOF_DCTELEM)], mm0
102        movq    MMWORD [MMBLOCK(3,0,edi,SIZEOF_DCTELEM)], mm3
103        movq    MMWORD [MMBLOCK(3,1,edi,SIZEOF_DCTELEM)], mm4
104
105        add     esi, byte 4*SIZEOF_JSAMPROW
106        add     edi, byte 4*DCTSIZE*SIZEOF_DCTELEM
107        dec     ecx
108        jnz     short .convloop
109
110        emms            ; empty MMX state
111
112        pop     edi
113        pop     esi
114;       pop     edx             ; need not be preserved
115;       pop     ecx             ; need not be preserved
116        pop     ebx
117        pop     ebp
118        ret
119
120; --------------------------------------------------------------------------
121;
122; Quantize/descale the coefficients, and store into coef_block
123;
124; This implementation is based on an algorithm described in
125;   "How to optimize for the Pentium family of microprocessors"
126;   (http://www.agner.org/assem/).
127;
128; GLOBAL(void)
129; jsimd_quantize_mmx (JCOEFPTR coef_block, DCTELEM * divisors,
130;                     DCTELEM * workspace);
131;
132
133%define RECIPROCAL(m,n,b) MMBLOCK(DCTSIZE*0+(m),(n),(b),SIZEOF_DCTELEM)
134%define CORRECTION(m,n,b) MMBLOCK(DCTSIZE*1+(m),(n),(b),SIZEOF_DCTELEM)
135%define SCALE(m,n,b)      MMBLOCK(DCTSIZE*2+(m),(n),(b),SIZEOF_DCTELEM)
136%define SHIFT(m,n,b)      MMBLOCK(DCTSIZE*3+(m),(n),(b),SIZEOF_DCTELEM)
137
138%define coef_block      ebp+8           ; JCOEFPTR coef_block
139%define divisors        ebp+12          ; DCTELEM * divisors
140%define workspace       ebp+16          ; DCTELEM * workspace
141
142        align   16
143        global  EXTN(jsimd_quantize_mmx)
144
145EXTN(jsimd_quantize_mmx):
146        push    ebp
147        mov     ebp,esp
148;       push    ebx             ; unused
149;       push    ecx             ; unused
150;       push    edx             ; need not be preserved
151        push    esi
152        push    edi
153
154        mov     esi, POINTER [workspace]
155        mov     edx, POINTER [divisors]
156        mov     edi, JCOEFPTR [coef_block]
157        mov     ah, 2
158        alignx  16,7
159.quantloop1:
160        mov     al, DCTSIZE2/8/2
161        alignx  16,7
162.quantloop2:
163        movq    mm2, MMWORD [MMBLOCK(0,0,esi,SIZEOF_DCTELEM)]
164        movq    mm3, MMWORD [MMBLOCK(0,1,esi,SIZEOF_DCTELEM)]
165
166        movq    mm0,mm2
167        movq    mm1,mm3
168
169        psraw   mm2,(WORD_BIT-1)  ; -1 if value < 0, 0 otherwise
170        psraw   mm3,(WORD_BIT-1)
171
172        pxor    mm0,mm2   ; val = -val
173        pxor    mm1,mm3
174        psubw   mm0,mm2
175        psubw   mm1,mm3
176
177        ;
178        ; MMX is an annoyingly crappy instruction set. It has two
179        ; misfeatures that are causing problems here:
180        ;
181        ; - All multiplications are signed.
182        ;
183        ; - The second operand for the shifts is not treated as packed.
184        ;
185        ;
186        ; We work around the first problem by implementing this algorithm:
187        ;
188        ; unsigned long unsigned_multiply(unsigned short x, unsigned short y)
189        ; {
190        ;   enum { SHORT_BIT = 16 };
191        ;   signed short sx = (signed short) x;
192        ;   signed short sy = (signed short) y;
193        ;   signed long sz;
194        ;
195        ;   sz = (long) sx * (long) sy;     /* signed multiply */
196        ;
197        ;   if (sx < 0) sz += (long) sy << SHORT_BIT;
198        ;   if (sy < 0) sz += (long) sx << SHORT_BIT;
199        ;
200        ;   return (unsigned long) sz;
201        ; }
202        ;
203        ; (note that a negative sx adds _sy_ and vice versa)
204        ;
205        ; For the second problem, we replace the shift by a multiplication.
206        ; Unfortunately that means we have to deal with the signed issue again.
207        ;
208
209        paddw   mm0, MMWORD [CORRECTION(0,0,edx)]   ; correction + roundfactor
210        paddw   mm1, MMWORD [CORRECTION(0,1,edx)]
211
212        movq    mm4,mm0   ; store current value for later
213        movq    mm5,mm1
214        pmulhw  mm0, MMWORD [RECIPROCAL(0,0,edx)]   ; reciprocal
215        pmulhw  mm1, MMWORD [RECIPROCAL(0,1,edx)]
216        paddw   mm0,mm4         ; reciprocal is always negative (MSB=1),
217        paddw   mm1,mm5   ; so we always need to add the initial value
218                        ; (input value is never negative as we
219                        ; inverted it at the start of this routine)
220
221        ; here it gets a bit tricky as both scale
222        ; and mm0/mm1 can be negative
223        movq    mm6, MMWORD [SCALE(0,0,edx)]    ; scale
224        movq    mm7, MMWORD [SCALE(0,1,edx)]
225        movq    mm4,mm0
226        movq    mm5,mm1
227        pmulhw  mm0,mm6
228        pmulhw  mm1,mm7
229
230        psraw   mm6,(WORD_BIT-1)    ; determine if scale is negative
231        psraw   mm7,(WORD_BIT-1)
232
233        pand    mm6,mm4             ; and add input if it is
234        pand    mm7,mm5
235        paddw   mm0,mm6
236        paddw   mm1,mm7
237
238        psraw   mm4,(WORD_BIT-1)    ; then check if negative input
239        psraw   mm5,(WORD_BIT-1)
240
241        pand    mm4, MMWORD [SCALE(0,0,edx)]    ; and add scale if it is
242        pand    mm5, MMWORD [SCALE(0,1,edx)]
243        paddw   mm0,mm4
244        paddw   mm1,mm5
245
246        pxor    mm0,mm2   ; val = -val
247        pxor    mm1,mm3
248        psubw   mm0,mm2
249        psubw   mm1,mm3
250
251        movq    MMWORD [MMBLOCK(0,0,edi,SIZEOF_DCTELEM)], mm0
252        movq    MMWORD [MMBLOCK(0,1,edi,SIZEOF_DCTELEM)], mm1
253
254        add     esi, byte 8*SIZEOF_DCTELEM
255        add     edx, byte 8*SIZEOF_DCTELEM
256        add     edi, byte 8*SIZEOF_JCOEF
257        dec     al
258        jnz     near .quantloop2
259        dec     ah
260        jnz     near .quantloop1        ; to avoid branch misprediction
261
262        emms            ; empty MMX state
263
264        pop     edi
265        pop     esi
266;       pop     edx             ; need not be preserved
267;       pop     ecx             ; unused
268;       pop     ebx             ; unused
269        pop     ebp
270        ret
271
272; For some reason, the OS X linker does not honor the request to align the
273; segment unless we do this.
274        align   16
275