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