1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
|
/* Intel SIMD SSE2 implementation of Viterbi ACS butterflies
for 256-state (k=9) convolutional code
Copyright 2004 Phil Karn, KA9Q
This code may be used under the terms of the GNU Lesser General Public License (LGPL)
void update_viterbi29_blk_sse2(struct v29 *vp,unsigned char *syms,int nbits) ;
*/
# SSE2 (128-bit integer SIMD) version
# Requires Pentium 4 or better
# These are offsets into struct v29, defined in viterbi29.h
.set DP,512
.set OLDMETRICS,516
.set NEWMETRICS,520
.text
.global update_viterbi29_blk_sse2,Branchtab29_sse2
.type update_viterbi29_blk_sse2,@function
.align 16
update_viterbi29_blk_sse2:
pushl %ebp
movl %esp,%ebp
pushl %esi
pushl %edi
pushl %edx
pushl %ebx
movl 8(%ebp),%edx # edx = vp
testl %edx,%edx
jnz 0f
movl -1,%eax
jmp err
0: movl OLDMETRICS(%edx),%esi # esi -> old metrics
movl NEWMETRICS(%edx),%edi # edi -> new metrics
movl DP(%edx),%edx # edx -> decisions
1: movl 16(%ebp),%eax # eax = nbits
decl %eax
jl 2f # passed zero, we're done
movl %eax,16(%ebp)
xorl %eax,%eax
movl 12(%ebp),%ebx # ebx = syms
movb (%ebx),%al
movd %eax,%xmm6 # xmm6[0] = first symbol
movb 1(%ebx),%al
movd %eax,%xmm5 # xmm5[0] = second symbol
addl $2,%ebx
movl %ebx,12(%ebp)
punpcklbw %xmm6,%xmm6 # xmm6[1] = xmm6[0]
punpcklbw %xmm5,%xmm5
movdqa thirtyones,%xmm7
pshuflw $0,%xmm6,%xmm6 # copy low word to low 3
pshuflw $0,%xmm5,%xmm5
punpcklqdq %xmm6,%xmm6 # propagate to all 16
punpcklqdq %xmm5,%xmm5
# xmm6 now contains first symbol in each byte, xmm5 the second
movdqa thirtyones,%xmm7
# each invocation of this macro does 16 butterflies in parallel
.MACRO butterfly GROUP
# compute branch metrics
movdqa Branchtab29_sse2+(16*\GROUP),%xmm4
movdqa Branchtab29_sse2+128+(16*\GROUP),%xmm3
pxor %xmm6,%xmm4
pxor %xmm5,%xmm3
pavgb %xmm3,%xmm4
psrlw $3,%xmm4
pand %xmm7,%xmm4 # xmm4 contains branch metrics
movdqa (16*\GROUP)(%esi),%xmm0 # Incoming path metric, high bit = 0
movdqa ((16*\GROUP)+128)(%esi),%xmm3 # Incoming path metric, high bit = 1
movdqa %xmm0,%xmm2
movdqa %xmm3,%xmm1
paddusb %xmm4,%xmm0
paddusb %xmm4,%xmm3
# invert branch metrics
pxor %xmm7,%xmm4
paddusb %xmm4,%xmm1
paddusb %xmm4,%xmm2
# Find survivors, leave in mm0,2
pminub %xmm1,%xmm0
pminub %xmm3,%xmm2
# get decisions, leave in mm1,3
pcmpeqb %xmm0,%xmm1
pcmpeqb %xmm2,%xmm3
# interleave and store new branch metrics in mm0,2
movdqa %xmm0,%xmm4
punpckhbw %xmm2,%xmm0 # interleave second 16 new metrics
punpcklbw %xmm2,%xmm4 # interleave first 16 new metrics
movdqa %xmm0,(32*\GROUP+16)(%edi)
movdqa %xmm4,(32*\GROUP)(%edi)
# interleave decisions & store
movdqa %xmm1,%xmm4
punpckhbw %xmm3,%xmm1
punpcklbw %xmm3,%xmm4
# work around bug in gas due to Intel doc error
.byte 0x66,0x0f,0xd7,0xd9 # pmovmskb %xmm1,%ebx
shll $16,%ebx
.byte 0x66,0x0f,0xd7,0xc4 # pmovmskb %xmm4,%eax
orl %eax,%ebx
movl %ebx,(4*\GROUP)(%edx)
.endm
# invoke macro 8 times for a total of 128 butterflies
butterfly GROUP=0
butterfly GROUP=1
butterfly GROUP=2
butterfly GROUP=3
butterfly GROUP=4
butterfly GROUP=5
butterfly GROUP=6
butterfly GROUP=7
addl $32,%edx # bump decision pointer
# see if we have to normalize
movl (%edi),%eax # extract first output metric
andl $255,%eax
cmp $50,%eax # is it greater than 50?
movl $0,%eax
jle done # No, no need to normalize
# Normalize by finding smallest metric and subtracting it
# from all metrics
movdqa (%edi),%xmm0
pminub 16(%edi),%xmm0
pminub 32(%edi),%xmm0
pminub 48(%edi),%xmm0
pminub 64(%edi),%xmm0
pminub 80(%edi),%xmm0
pminub 96(%edi),%xmm0
pminub 112(%edi),%xmm0
pminub 128(%edi),%xmm0
pminub 144(%edi),%xmm0
pminub 160(%edi),%xmm0
pminub 176(%edi),%xmm0
pminub 192(%edi),%xmm0
pminub 208(%edi),%xmm0
pminub 224(%edi),%xmm0
pminub 240(%edi),%xmm0
# crunch down to single lowest metric
movdqa %xmm0,%xmm1
psrldq $8,%xmm0 # the count to psrldq is bytes, not bits!
pminub %xmm1,%xmm0
movdqa %xmm0,%xmm1
psrlq $32,%xmm0
pminub %xmm1,%xmm0
movdqa %xmm0,%xmm1
psrlq $16,%xmm0
pminub %xmm1,%xmm0
movdqa %xmm0,%xmm1
psrlq $8,%xmm0
pminub %xmm1,%xmm0
punpcklbw %xmm0,%xmm0 # lowest 2 bytes
pshuflw $0,%xmm0,%xmm0 # lowest 8 bytes
punpcklqdq %xmm0,%xmm0 # all 16 bytes
# xmm0 now contains lowest metric in all 16 bytes
# subtract it from every output metric
movdqa (%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,(%edi)
movdqa 16(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,16(%edi)
movdqa 32(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,32(%edi)
movdqa 48(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,48(%edi)
movdqa 64(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,64(%edi)
movdqa 80(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,80(%edi)
movdqa 96(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,96(%edi)
movdqa 112(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,112(%edi)
movdqa 128(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,128(%edi)
movdqa 144(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,144(%edi)
movdqa 160(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,160(%edi)
movdqa 176(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,176(%edi)
movdqa 192(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,192(%edi)
movdqa 208(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,208(%edi)
movdqa 224(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,224(%edi)
movdqa 240(%edi),%xmm1
psubusb %xmm0,%xmm1
movdqa %xmm1,240(%edi)
done:
# swap metrics
movl %esi,%eax
movl %edi,%esi
movl %eax,%edi
jmp 1b
2: movl 8(%ebp),%ebx # ebx = vp
# stash metric pointers
movl %esi,OLDMETRICS(%ebx)
movl %edi,NEWMETRICS(%ebx)
movl %edx,DP(%ebx) # stash incremented value of vp->dp
xorl %eax,%eax
err: popl %ebx
popl %edx
popl %edi
popl %esi
popl %ebp
ret
.data
.align 16
thirtyones:
.byte 31,31,31,31,31,31,31,31,31,31,31,31,31,31,31,31
|
