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1;
2; jchuff-sse2.asm - Huffman entropy encoding (SSE2)
3;
4; Copyright (C) 2009-2011, 2014-2017, D. R. Commander.
5; Copyright (C) 2015, Matthieu Darbois.
6;
7; Based on the 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; This file contains an SSE2 implementation for Huffman coding of one block.
18; The following code is based directly on jchuff.c; see jchuff.c for more
19; details.
20;
21; [TAB8]
22
23%include "jsimdext.inc"
24
25; --------------------------------------------------------------------------
26    SECTION     SEG_CONST
27
28    alignz      32
29    GLOBAL_DATA(jconst_huff_encode_one_block)
30
31EXTN(jconst_huff_encode_one_block):
32
33%include "jpeg_nbits_table.inc"
34
35    alignz      32
36
37; --------------------------------------------------------------------------
38    SECTION     SEG_TEXT
39    BITS        32
40
41; These macros perform the same task as the emit_bits() function in the
42; original libjpeg code.  In addition to reducing overhead by explicitly
43; inlining the code, additional performance is achieved by taking into
44; account the size of the bit buffer and waiting until it is almost full
45; before emptying it.  This mostly benefits 64-bit platforms, since 6
46; bytes can be stored in a 64-bit bit buffer before it has to be emptied.
47
48%macro EMIT_BYTE 0
49    sub         put_bits, 8             ; put_bits -= 8;
50    mov         edx, put_buffer
51    mov         ecx, put_bits
52    shr         edx, cl                 ; c = (JOCTET)GETJOCTET(put_buffer >> put_bits);
53    mov         byte [eax], dl          ; *buffer++ = c;
54    add         eax, 1
55    cmp         dl, 0xFF                ; need to stuff a zero byte?
56    jne         %%.EMIT_BYTE_END
57    mov         byte [eax], 0           ; *buffer++ = 0;
58    add         eax, 1
59%%.EMIT_BYTE_END:
60%endmacro
61
62%macro PUT_BITS 1
63    add         put_bits, ecx           ; put_bits += size;
64    shl         put_buffer, cl          ; put_buffer = (put_buffer << size);
65    or          put_buffer, %1
66%endmacro
67
68%macro CHECKBUF15 0
69    cmp         put_bits, 16            ; if (put_bits > 31) {
70    jl          %%.CHECKBUF15_END
71    mov         eax, POINTER [esp+buffer]
72    EMIT_BYTE
73    EMIT_BYTE
74    mov         POINTER [esp+buffer], eax
75%%.CHECKBUF15_END:
76%endmacro
77
78%macro EMIT_BITS 1
79    PUT_BITS    %1
80    CHECKBUF15
81%endmacro
82
83%macro kloop_prepare 37                 ;(ko, jno0, ..., jno31, xmm0, xmm1, xmm2, xmm3)
84    pxor        xmm4, xmm4              ; __m128i neg = _mm_setzero_si128();
85    pxor        xmm5, xmm5              ; __m128i neg = _mm_setzero_si128();
86    pxor        xmm6, xmm6              ; __m128i neg = _mm_setzero_si128();
87    pxor        xmm7, xmm7              ; __m128i neg = _mm_setzero_si128();
88    pinsrw      %34, word [esi + %2  * SIZEOF_WORD], 0  ; xmm_shadow[0] = block[jno0];
89    pinsrw      %35, word [esi + %10 * SIZEOF_WORD], 0  ; xmm_shadow[8] = block[jno8];
90    pinsrw      %36, word [esi + %18 * SIZEOF_WORD], 0  ; xmm_shadow[16] = block[jno16];
91    pinsrw      %37, word [esi + %26 * SIZEOF_WORD], 0  ; xmm_shadow[24] = block[jno24];
92    pinsrw      %34, word [esi + %3  * SIZEOF_WORD], 1  ; xmm_shadow[1] = block[jno1];
93    pinsrw      %35, word [esi + %11 * SIZEOF_WORD], 1  ; xmm_shadow[9] = block[jno9];
94    pinsrw      %36, word [esi + %19 * SIZEOF_WORD], 1  ; xmm_shadow[17] = block[jno17];
95    pinsrw      %37, word [esi + %27 * SIZEOF_WORD], 1  ; xmm_shadow[25] = block[jno25];
96    pinsrw      %34, word [esi + %4  * SIZEOF_WORD], 2  ; xmm_shadow[2] = block[jno2];
97    pinsrw      %35, word [esi + %12 * SIZEOF_WORD], 2  ; xmm_shadow[10] = block[jno10];
98    pinsrw      %36, word [esi + %20 * SIZEOF_WORD], 2  ; xmm_shadow[18] = block[jno18];
99    pinsrw      %37, word [esi + %28 * SIZEOF_WORD], 2  ; xmm_shadow[26] = block[jno26];
100    pinsrw      %34, word [esi + %5  * SIZEOF_WORD], 3  ; xmm_shadow[3] = block[jno3];
101    pinsrw      %35, word [esi + %13 * SIZEOF_WORD], 3  ; xmm_shadow[11] = block[jno11];
102    pinsrw      %36, word [esi + %21 * SIZEOF_WORD], 3  ; xmm_shadow[19] = block[jno19];
103    pinsrw      %37, word [esi + %29 * SIZEOF_WORD], 3  ; xmm_shadow[27] = block[jno27];
104    pinsrw      %34, word [esi + %6  * SIZEOF_WORD], 4  ; xmm_shadow[4] = block[jno4];
105    pinsrw      %35, word [esi + %14 * SIZEOF_WORD], 4  ; xmm_shadow[12] = block[jno12];
106    pinsrw      %36, word [esi + %22 * SIZEOF_WORD], 4  ; xmm_shadow[20] = block[jno20];
107    pinsrw      %37, word [esi + %30 * SIZEOF_WORD], 4  ; xmm_shadow[28] = block[jno28];
108    pinsrw      %34, word [esi + %7  * SIZEOF_WORD], 5  ; xmm_shadow[5] = block[jno5];
109    pinsrw      %35, word [esi + %15 * SIZEOF_WORD], 5  ; xmm_shadow[13] = block[jno13];
110    pinsrw      %36, word [esi + %23 * SIZEOF_WORD], 5  ; xmm_shadow[21] = block[jno21];
111    pinsrw      %37, word [esi + %31 * SIZEOF_WORD], 5  ; xmm_shadow[29] = block[jno29];
112    pinsrw      %34, word [esi + %8  * SIZEOF_WORD], 6  ; xmm_shadow[6] = block[jno6];
113    pinsrw      %35, word [esi + %16 * SIZEOF_WORD], 6  ; xmm_shadow[14] = block[jno14];
114    pinsrw      %36, word [esi + %24 * SIZEOF_WORD], 6  ; xmm_shadow[22] = block[jno22];
115    pinsrw      %37, word [esi + %32 * SIZEOF_WORD], 6  ; xmm_shadow[30] = block[jno30];
116    pinsrw      %34, word [esi + %9  * SIZEOF_WORD], 7  ; xmm_shadow[7] = block[jno7];
117    pinsrw      %35, word [esi + %17 * SIZEOF_WORD], 7  ; xmm_shadow[15] = block[jno15];
118    pinsrw      %36, word [esi + %25 * SIZEOF_WORD], 7  ; xmm_shadow[23] = block[jno23];
119%if %1 != 32
120    pinsrw      %37, word [esi + %33 * SIZEOF_WORD], 7  ; xmm_shadow[31] = block[jno31];
121%else
122    pinsrw      %37, ecx, 7             ; xmm_shadow[31] = block[jno31];
123%endif
124    pcmpgtw     xmm4, %34               ; neg = _mm_cmpgt_epi16(neg, x1);
125    pcmpgtw     xmm5, %35               ; neg = _mm_cmpgt_epi16(neg, x1);
126    pcmpgtw     xmm6, %36               ; neg = _mm_cmpgt_epi16(neg, x1);
127    pcmpgtw     xmm7, %37               ; neg = _mm_cmpgt_epi16(neg, x1);
128    paddw       %34, xmm4               ; x1 = _mm_add_epi16(x1, neg);
129    paddw       %35, xmm5               ; x1 = _mm_add_epi16(x1, neg);
130    paddw       %36, xmm6               ; x1 = _mm_add_epi16(x1, neg);
131    paddw       %37, xmm7               ; x1 = _mm_add_epi16(x1, neg);
132    pxor        %34, xmm4               ; x1 = _mm_xor_si128(x1, neg);
133    pxor        %35, xmm5               ; x1 = _mm_xor_si128(x1, neg);
134    pxor        %36, xmm6               ; x1 = _mm_xor_si128(x1, neg);
135    pxor        %37, xmm7               ; x1 = _mm_xor_si128(x1, neg);
136    pxor        xmm4, %34               ; neg = _mm_xor_si128(neg, x1);
137    pxor        xmm5, %35               ; neg = _mm_xor_si128(neg, x1);
138    pxor        xmm6, %36               ; neg = _mm_xor_si128(neg, x1);
139    pxor        xmm7, %37               ; neg = _mm_xor_si128(neg, x1);
140    movdqa      XMMWORD [esp + t1 + %1 * SIZEOF_WORD], %34          ; _mm_storeu_si128((__m128i *)(t1 + ko), x1);
141    movdqa      XMMWORD [esp + t1 + (%1 + 8) * SIZEOF_WORD], %35    ; _mm_storeu_si128((__m128i *)(t1 + ko + 8), x1);
142    movdqa      XMMWORD [esp + t1 + (%1 + 16) * SIZEOF_WORD], %36   ; _mm_storeu_si128((__m128i *)(t1 + ko + 16), x1);
143    movdqa      XMMWORD [esp + t1 + (%1 + 24) * SIZEOF_WORD], %37   ; _mm_storeu_si128((__m128i *)(t1 + ko + 24), x1);
144    movdqa      XMMWORD [esp + t2 + %1 * SIZEOF_WORD], xmm4         ; _mm_storeu_si128((__m128i *)(t2 + ko), neg);
145    movdqa      XMMWORD [esp + t2 + (%1 + 8) * SIZEOF_WORD], xmm5   ; _mm_storeu_si128((__m128i *)(t2 + ko + 8), neg);
146    movdqa      XMMWORD [esp + t2 + (%1 + 16) * SIZEOF_WORD], xmm6  ; _mm_storeu_si128((__m128i *)(t2 + ko + 16), neg);
147    movdqa      XMMWORD [esp + t2 + (%1 + 24) * SIZEOF_WORD], xmm7  ; _mm_storeu_si128((__m128i *)(t2 + ko + 24), neg);
148%endmacro
149
150;
151; Encode a single block's worth of coefficients.
152;
153; GLOBAL(JOCTET *)
154; jsimd_huff_encode_one_block_sse2(working_state *state, JOCTET *buffer,
155;                                  JCOEFPTR block, int last_dc_val,
156;                                  c_derived_tbl *dctbl, c_derived_tbl *actbl)
157;
158
159; eax + 8 = working_state *state
160; eax + 12 = JOCTET *buffer
161; eax + 16 = JCOEFPTR block
162; eax + 20 = int last_dc_val
163; eax + 24 = c_derived_tbl *dctbl
164; eax + 28 = c_derived_tbl *actbl
165
166%define pad         6 * SIZEOF_DWORD    ; Align to 16 bytes
167%define t1          pad
168%define t2          t1 + (DCTSIZE2 * SIZEOF_WORD)
169%define block       t2 + (DCTSIZE2 * SIZEOF_WORD)
170%define actbl       block + SIZEOF_DWORD
171%define buffer      actbl + SIZEOF_DWORD
172%define temp        buffer + SIZEOF_DWORD
173%define temp2       temp + SIZEOF_DWORD
174%define temp3       temp2 + SIZEOF_DWORD
175%define temp4       temp3 + SIZEOF_DWORD
176%define temp5       temp4 + SIZEOF_DWORD
177%define gotptr      temp5 + SIZEOF_DWORD  ; void *gotptr
178%define put_buffer  ebx
179%define put_bits    edi
180
181    align       32
182    GLOBAL_FUNCTION(jsimd_huff_encode_one_block_sse2)
183
184EXTN(jsimd_huff_encode_one_block_sse2):
185    push        ebp
186    mov         eax, esp                     ; eax = original ebp
187    sub         esp, byte 4
188    and         esp, byte (-SIZEOF_XMMWORD)  ; align to 128 bits
189    mov         [esp], eax
190    mov         ebp, esp                     ; ebp = aligned ebp
191    sub         esp, temp5+9*SIZEOF_DWORD-pad
192    push        ebx
193    push        ecx
194;   push        edx                     ; need not be preserved
195    push        esi
196    push        edi
197    push        ebp
198
199    mov         esi, POINTER [eax+8]       ; (working_state *state)
200    mov         put_buffer, DWORD [esi+8]  ; put_buffer = state->cur.put_buffer;
201    mov         put_bits, DWORD [esi+12]   ; put_bits = state->cur.put_bits;
202    push        esi                        ; esi is now scratch
203
204    get_GOT     edx                        ; get GOT address
205    movpic      POINTER [esp+gotptr], edx  ; save GOT address
206
207    mov         ecx, POINTER [eax+28]
208    mov         edx, POINTER [eax+16]
209    mov         esi, POINTER [eax+12]
210    mov         POINTER [esp+actbl], ecx
211    mov         POINTER [esp+block], edx
212    mov         POINTER [esp+buffer], esi
213
214    ; Encode the DC coefficient difference per section F.1.2.1
215    mov         esi, POINTER [esp+block]  ; block
216    movsx       ecx, word [esi]           ; temp = temp2 = block[0] - last_dc_val;
217    sub         ecx, DWORD [eax+20]
218    mov         esi, ecx
219
220    ; This is a well-known technique for obtaining the absolute value
221    ; with out a branch.  It is derived from an assembly language technique
222    ; presented in "How to Optimize for the Pentium Processors",
223    ; Copyright (c) 1996, 1997 by Agner Fog.
224    mov         edx, ecx
225    sar         edx, 31                 ; temp3 = temp >> (CHAR_BIT * sizeof(int) - 1);
226    xor         ecx, edx                ; temp ^= temp3;
227    sub         ecx, edx                ; temp -= temp3;
228
229    ; For a negative input, want temp2 = bitwise complement of abs(input)
230    ; This code assumes we are on a two's complement machine
231    add         esi, edx                ; temp2 += temp3;
232    mov         DWORD [esp+temp], esi   ; backup temp2 in temp
233
234    ; Find the number of bits needed for the magnitude of the coefficient
235    movpic      ebp, POINTER [esp+gotptr]                        ; load GOT address (ebp)
236    movzx       edx, byte [GOTOFF(ebp, jpeg_nbits_table + ecx)]  ; nbits = JPEG_NBITS(temp);
237    mov         DWORD [esp+temp2], edx                           ; backup nbits in temp2
238
239    ; Emit the Huffman-coded symbol for the number of bits
240    mov         ebp, POINTER [eax+24]         ; After this point, arguments are not accessible anymore
241    mov         eax,  INT [ebp + edx * 4]     ; code = dctbl->ehufco[nbits];
242    movzx       ecx, byte [ebp + edx + 1024]  ; size = dctbl->ehufsi[nbits];
243    EMIT_BITS   eax                           ; EMIT_BITS(code, size)
244
245    mov         ecx, DWORD [esp+temp2]        ; restore nbits
246
247    ; Mask off any extra bits in code
248    mov         eax, 1
249    shl         eax, cl
250    dec         eax
251    and         eax, DWORD [esp+temp]   ; temp2 &= (((JLONG)1)<<nbits) - 1;
252
253    ; Emit that number of bits of the value, if positive,
254    ; or the complement of its magnitude, if negative.
255    EMIT_BITS   eax                     ; EMIT_BITS(temp2, nbits)
256
257    ; Prepare data
258    xor         ecx, ecx
259    mov         esi, POINTER [esp+block]
260    kloop_prepare  0,  1,  8,  16, 9,  2,  3,  10, 17, 24, 32, 25, \
261                   18, 11, 4,  5,  12, 19, 26, 33, 40, 48, 41, 34, \
262                   27, 20, 13, 6,  7,  14, 21, 28, 35, \
263                   xmm0, xmm1, xmm2, xmm3
264    kloop_prepare  32, 42, 49, 56, 57, 50, 43, 36, 29, 22, 15, 23, \
265                   30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, \
266                   53, 60, 61, 54, 47, 55, 62, 63, 63, \
267                   xmm0, xmm1, xmm2, xmm3
268
269    pxor        xmm7, xmm7
270    movdqa      xmm0, XMMWORD [esp + t1 + 0 * SIZEOF_WORD]   ; __m128i tmp0 = _mm_loadu_si128((__m128i *)(t1 + 0));
271    movdqa      xmm1, XMMWORD [esp + t1 + 8 * SIZEOF_WORD]   ; __m128i tmp1 = _mm_loadu_si128((__m128i *)(t1 + 8));
272    movdqa      xmm2, XMMWORD [esp + t1 + 16 * SIZEOF_WORD]  ; __m128i tmp2 = _mm_loadu_si128((__m128i *)(t1 + 16));
273    movdqa      xmm3, XMMWORD [esp + t1 + 24 * SIZEOF_WORD]  ; __m128i tmp3 = _mm_loadu_si128((__m128i *)(t1 + 24));
274    pcmpeqw     xmm0, xmm7              ; tmp0 = _mm_cmpeq_epi16(tmp0, zero);
275    pcmpeqw     xmm1, xmm7              ; tmp1 = _mm_cmpeq_epi16(tmp1, zero);
276    pcmpeqw     xmm2, xmm7              ; tmp2 = _mm_cmpeq_epi16(tmp2, zero);
277    pcmpeqw     xmm3, xmm7              ; tmp3 = _mm_cmpeq_epi16(tmp3, zero);
278    packsswb    xmm0, xmm1              ; tmp0 = _mm_packs_epi16(tmp0, tmp1);
279    packsswb    xmm2, xmm3              ; tmp2 = _mm_packs_epi16(tmp2, tmp3);
280    pmovmskb    edx, xmm0               ; index  = ((uint64_t)_mm_movemask_epi8(tmp0)) << 0;
281    pmovmskb    ecx, xmm2               ; index  = ((uint64_t)_mm_movemask_epi8(tmp2)) << 16;
282    shl         ecx, 16
283    or          edx, ecx
284    not         edx                     ; index = ~index;
285
286    lea         esi, [esp+t1]
287    mov         ebp, POINTER [esp+actbl]  ; ebp = actbl
288
289.BLOOP:
290    bsf         ecx, edx                ; r = __builtin_ctzl(index);
291    jz          near .ELOOP
292    lea         esi, [esi+ecx*2]        ; k += r;
293    shr         edx, cl                 ; index >>= r;
294    mov         DWORD [esp+temp3], edx
295.BRLOOP:
296    cmp         ecx, 16                       ; while (r > 15) {
297    jl          near .ERLOOP
298    sub         ecx, 16                       ; r -= 16;
299    mov         DWORD [esp+temp], ecx
300    mov         eax, INT [ebp + 240 * 4]      ; code_0xf0 = actbl->ehufco[0xf0];
301    movzx       ecx, byte [ebp + 1024 + 240]  ; size_0xf0 = actbl->ehufsi[0xf0];
302    EMIT_BITS   eax                           ; EMIT_BITS(code_0xf0, size_0xf0)
303    mov         ecx, DWORD [esp+temp]
304    jmp         .BRLOOP
305.ERLOOP:
306    movsx       eax, word [esi]                                  ; temp = t1[k];
307    movpic      edx, POINTER [esp+gotptr]                        ; load GOT address (edx)
308    movzx       eax, byte [GOTOFF(edx, jpeg_nbits_table + eax)]  ; nbits = JPEG_NBITS(temp);
309    mov         DWORD [esp+temp2], eax
310    ; Emit Huffman symbol for run length / number of bits
311    shl         ecx, 4                        ; temp3 = (r << 4) + nbits;
312    add         ecx, eax
313    mov         eax,  INT [ebp + ecx * 4]     ; code = actbl->ehufco[temp3];
314    movzx       ecx, byte [ebp + ecx + 1024]  ; size = actbl->ehufsi[temp3];
315    EMIT_BITS   eax
316
317    movsx       edx, word [esi+DCTSIZE2*2]    ; temp2 = t2[k];
318    ; Mask off any extra bits in code
319    mov         ecx, DWORD [esp+temp2]
320    mov         eax, 1
321    shl         eax, cl
322    dec         eax
323    and         eax, edx                ; temp2 &= (((JLONG)1)<<nbits) - 1;
324    EMIT_BITS   eax                     ; PUT_BITS(temp2, nbits)
325    mov         edx, DWORD [esp+temp3]
326    add         esi, 2                  ; ++k;
327    shr         edx, 1                  ; index >>= 1;
328
329    jmp         .BLOOP
330.ELOOP:
331    movdqa      xmm0, XMMWORD [esp + t1 + 32 * SIZEOF_WORD]  ; __m128i tmp0 = _mm_loadu_si128((__m128i *)(t1 + 0));
332    movdqa      xmm1, XMMWORD [esp + t1 + 40 * SIZEOF_WORD]  ; __m128i tmp1 = _mm_loadu_si128((__m128i *)(t1 + 8));
333    movdqa      xmm2, XMMWORD [esp + t1 + 48 * SIZEOF_WORD]  ; __m128i tmp2 = _mm_loadu_si128((__m128i *)(t1 + 16));
334    movdqa      xmm3, XMMWORD [esp + t1 + 56 * SIZEOF_WORD]  ; __m128i tmp3 = _mm_loadu_si128((__m128i *)(t1 + 24));
335    pcmpeqw     xmm0, xmm7              ; tmp0 = _mm_cmpeq_epi16(tmp0, zero);
336    pcmpeqw     xmm1, xmm7              ; tmp1 = _mm_cmpeq_epi16(tmp1, zero);
337    pcmpeqw     xmm2, xmm7              ; tmp2 = _mm_cmpeq_epi16(tmp2, zero);
338    pcmpeqw     xmm3, xmm7              ; tmp3 = _mm_cmpeq_epi16(tmp3, zero);
339    packsswb    xmm0, xmm1              ; tmp0 = _mm_packs_epi16(tmp0, tmp1);
340    packsswb    xmm2, xmm3              ; tmp2 = _mm_packs_epi16(tmp2, tmp3);
341    pmovmskb    edx, xmm0               ; index  = ((uint64_t)_mm_movemask_epi8(tmp0)) << 0;
342    pmovmskb    ecx, xmm2               ; index  = ((uint64_t)_mm_movemask_epi8(tmp2)) << 16;
343    shl         ecx, 16
344    or          edx, ecx
345    not         edx                     ; index = ~index;
346
347    lea         eax, [esp + t1 + (DCTSIZE2/2) * 2]
348    sub         eax, esi
349    shr         eax, 1
350    bsf         ecx, edx                ; r = __builtin_ctzl(index);
351    jz          near .ELOOP2
352    shr         edx, cl                 ; index >>= r;
353    add         ecx, eax
354    lea         esi, [esi+ecx*2]        ; k += r;
355    mov         DWORD [esp+temp3], edx
356    jmp         .BRLOOP2
357.BLOOP2:
358    bsf         ecx, edx                ; r = __builtin_ctzl(index);
359    jz          near .ELOOP2
360    lea         esi, [esi+ecx*2]        ; k += r;
361    shr         edx, cl                 ; index >>= r;
362    mov         DWORD [esp+temp3], edx
363.BRLOOP2:
364    cmp         ecx, 16                       ; while (r > 15) {
365    jl          near .ERLOOP2
366    sub         ecx, 16                       ; r -= 16;
367    mov         DWORD [esp+temp], ecx
368    mov         eax, INT [ebp + 240 * 4]      ; code_0xf0 = actbl->ehufco[0xf0];
369    movzx       ecx, byte [ebp + 1024 + 240]  ; size_0xf0 = actbl->ehufsi[0xf0];
370    EMIT_BITS   eax                           ; EMIT_BITS(code_0xf0, size_0xf0)
371    mov         ecx, DWORD [esp+temp]
372    jmp         .BRLOOP2
373.ERLOOP2:
374    movsx       eax, word [esi]         ; temp = t1[k];
375    bsr         eax, eax                ; nbits = 32 - __builtin_clz(temp);
376    inc         eax
377    mov         DWORD [esp+temp2], eax
378    ; Emit Huffman symbol for run length / number of bits
379    shl         ecx, 4                        ; temp3 = (r << 4) + nbits;
380    add         ecx, eax
381    mov         eax,  INT [ebp + ecx * 4]     ; code = actbl->ehufco[temp3];
382    movzx       ecx, byte [ebp + ecx + 1024]  ; size = actbl->ehufsi[temp3];
383    EMIT_BITS   eax
384
385    movsx       edx, word [esi+DCTSIZE2*2]    ; temp2 = t2[k];
386    ; Mask off any extra bits in code
387    mov         ecx, DWORD [esp+temp2]
388    mov         eax, 1
389    shl         eax, cl
390    dec         eax
391    and         eax, edx                ; temp2 &= (((JLONG)1)<<nbits) - 1;
392    EMIT_BITS   eax                     ; PUT_BITS(temp2, nbits)
393    mov         edx, DWORD [esp+temp3]
394    add         esi, 2                  ; ++k;
395    shr         edx, 1                  ; index >>= 1;
396
397    jmp         .BLOOP2
398.ELOOP2:
399    ; If the last coef(s) were zero, emit an end-of-block code
400    lea         edx, [esp + t1 + (DCTSIZE2-1) * 2]  ; r = DCTSIZE2-1-k;
401    cmp         edx, esi                            ; if (r > 0) {
402    je          .EFN
403    mov         eax,  INT [ebp]                     ; code = actbl->ehufco[0];
404    movzx       ecx, byte [ebp + 1024]              ; size = actbl->ehufsi[0];
405    EMIT_BITS   eax
406.EFN:
407    mov         eax, [esp+buffer]
408    pop         esi
409    ; Save put_buffer & put_bits
410    mov         DWORD [esi+8], put_buffer  ; state->cur.put_buffer = put_buffer;
411    mov         DWORD [esi+12], put_bits   ; state->cur.put_bits = put_bits;
412
413    pop         ebp
414    pop         edi
415    pop         esi
416;   pop         edx                     ; need not be preserved
417    pop         ecx
418    pop         ebx
419    mov         esp, ebp                ; esp <- aligned ebp
420    pop         esp                     ; esp <- original ebp
421    pop         ebp
422    ret
423
424; For some reason, the OS X linker does not honor the request to align the
425; segment unless we do this.
426    align       32
427