Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* Intel SIMD SSE implementation of Viterbi ACS butterflies |
| 2 | for 256-state (k=9) convolutional code |
| 3 | Copyright 2004 Phil Karn, KA9Q |
| 4 | This code may be used under the terms of the GNU Lesser General Public License (LGPL) |
| 5 | |
| 6 | void update_viterbi29_blk_sse(struct v29 *vp,unsigned char syms[],int nbits); |
| 7 | */ |
| 8 | # SSE (64-bit integer SIMD) version |
| 9 | # Requires Pentium III or better |
| 10 | # These are offsets into struct v29, defined in viterbi29.h |
| 11 | .set DP,512 |
| 12 | .set OLDMETRICS,516 |
| 13 | .set NEWMETRICS,520 |
| 14 | .text |
| 15 | .global update_viterbi29_blk_sse,Branchtab29_sse |
| 16 | .type update_viterbi29_blk_sse,@function |
| 17 | .align 16 |
| 18 | |
| 19 | update_viterbi29_blk_sse: |
| 20 | pushl %ebp |
| 21 | movl %esp,%ebp |
| 22 | pushl %esi |
| 23 | pushl %edi |
| 24 | pushl %edx |
| 25 | pushl %ebx |
| 26 | |
| 27 | movl 8(%ebp),%edx # edx = vp |
| 28 | testl %edx,%edx |
| 29 | jnz 0f |
| 30 | movl -1,%eax |
| 31 | jmp err |
| 32 | 0: movl OLDMETRICS(%edx),%esi # esi -> old metrics |
| 33 | movl NEWMETRICS(%edx),%edi # edi -> new metrics |
| 34 | movl DP(%edx),%edx # edx -> decisions |
| 35 | |
| 36 | 1: movl 16(%ebp),%eax # eax = nbits |
| 37 | decl %eax |
| 38 | jl 2f # passed zero, we're done |
| 39 | movl %eax,16(%ebp) |
| 40 | |
| 41 | xorl %eax,%eax |
| 42 | movl 12(%ebp),%ebx # ebx = syms |
| 43 | movb (%ebx),%al |
| 44 | movd %eax,%mm6 # mm6[0] = first symbol |
| 45 | movb 1(%ebx),%al |
| 46 | movd %eax,%mm5 # mm5[0] = second symbol |
| 47 | addl $2,%ebx |
| 48 | movl %ebx,12(%ebp) |
| 49 | |
| 50 | punpcklbw %mm6,%mm6 # mm6[1] = mm6[0] |
| 51 | punpcklbw %mm5,%mm5 |
| 52 | |
| 53 | movq thirtyones,%mm7 |
| 54 | pshufw $0,%mm6,%mm6 # copy low word to upper 3 |
| 55 | pshufw $0,%mm5,%mm5 |
| 56 | # mm6 now contains first symbol in each byte, mm5 the second |
| 57 | |
| 58 | # each invocation of this macro does 8 butterflies in parallel |
| 59 | .MACRO butterfly GROUP |
| 60 | # compute branch metrics |
| 61 | movq Branchtab29_sse+(8*\GROUP),%mm4 |
| 62 | movq Branchtab29_sse+128+(8*\GROUP),%mm3 |
| 63 | pxor %mm6,%mm4 |
| 64 | pxor %mm5,%mm3 |
| 65 | pavgb %mm3,%mm4 # mm4 contains branch metrics |
| 66 | psrlw $3,%mm4 |
| 67 | pand %mm7,%mm4 |
| 68 | |
| 69 | movq (8*\GROUP)(%esi),%mm0 # Incoming path metric, high bit = 0 |
| 70 | movq ((8*\GROUP)+128)(%esi),%mm3 # Incoming path metric, high bit = 1 |
| 71 | movq %mm0,%mm2 |
| 72 | movq %mm3,%mm1 |
| 73 | paddusb %mm4,%mm0 |
| 74 | paddusb %mm4,%mm3 |
| 75 | |
| 76 | # invert branch metrics. This works only because they're 5 bits |
| 77 | pxor %mm7,%mm4 |
| 78 | |
| 79 | paddusb %mm4,%mm1 |
| 80 | paddusb %mm4,%mm2 |
| 81 | |
| 82 | # Find survivors, leave in mm0,2 |
| 83 | pminub %mm1,%mm0 |
| 84 | pminub %mm3,%mm2 |
| 85 | # get decisions, leave in mm1,3 |
| 86 | pcmpeqb %mm0,%mm1 |
| 87 | pcmpeqb %mm2,%mm3 |
| 88 | |
| 89 | # interleave and store new branch metrics in mm0,2 |
| 90 | movq %mm0,%mm4 |
| 91 | punpckhbw %mm2,%mm0 # interleave second 8 new metrics |
| 92 | punpcklbw %mm2,%mm4 # interleave first 8 new metrics |
| 93 | movq %mm0,(16*\GROUP+8)(%edi) |
| 94 | movq %mm4,(16*\GROUP)(%edi) |
| 95 | |
| 96 | # interleave decisions, accumulate into %ebx |
| 97 | movq %mm1,%mm4 |
| 98 | punpckhbw %mm3,%mm1 |
| 99 | punpcklbw %mm3,%mm4 |
| 100 | # Due to an error in the Intel instruction set ref (the register |
| 101 | # fields are swapped), gas assembles pmovmskb incorrectly |
| 102 | # See http://mail.gnu.org/pipermail/bug-gnu-utils/2000-August/002341.html |
| 103 | .byte 0x0f,0xd7,0xc1 # pmovmskb %mm1,%eax |
| 104 | shll $((16*\GROUP+8)&31),%eax |
| 105 | orl %eax,%ebx |
| 106 | .byte 0x0f,0xd7,0xc4 # pmovmskb %mm4,%eax |
| 107 | shll $((16*\GROUP)&31),%eax |
| 108 | orl %eax,%ebx |
| 109 | .endm |
| 110 | |
| 111 | # invoke macro 16 times for a total of 128 butterflies |
| 112 | xorl %ebx,%ebx # clear decisions |
| 113 | butterfly GROUP=0 |
| 114 | butterfly GROUP=1 |
| 115 | movl %ebx,(%edx) # stash first 32 decisions |
| 116 | xorl %ebx,%ebx |
| 117 | butterfly GROUP=2 |
| 118 | butterfly GROUP=3 |
| 119 | movl %ebx,4(%edx) # stash second 32 decisions |
| 120 | xorl %ebx,%ebx # clear decisions |
| 121 | butterfly GROUP=4 |
| 122 | butterfly GROUP=5 |
| 123 | movl %ebx,8(%edx) # stash first 32 decisions |
| 124 | xorl %ebx,%ebx |
| 125 | butterfly GROUP=6 |
| 126 | butterfly GROUP=7 |
| 127 | movl %ebx,12(%edx) # stash second 32 decisions |
| 128 | xorl %ebx,%ebx # clear decisions |
| 129 | butterfly GROUP=8 |
| 130 | butterfly GROUP=9 |
| 131 | movl %ebx,16(%edx) # stash first 32 decisions |
| 132 | xorl %ebx,%ebx |
| 133 | butterfly GROUP=10 |
| 134 | butterfly GROUP=11 |
| 135 | movl %ebx,20(%edx) # stash second 32 decisions |
| 136 | xorl %ebx,%ebx # clear decisions |
| 137 | butterfly GROUP=12 |
| 138 | butterfly GROUP=13 |
| 139 | movl %ebx,24(%edx) # stash first 32 decisions |
| 140 | xorl %ebx,%ebx |
| 141 | butterfly GROUP=14 |
| 142 | butterfly GROUP=15 |
| 143 | movl %ebx,28(%edx) # stash second 32 decisions |
| 144 | |
| 145 | addl $32,%edx # bump decision pointer |
| 146 | |
| 147 | # see if we have to normalize |
| 148 | movl (%edi),%eax # extract first output metric |
| 149 | andl $255,%eax |
| 150 | cmp $50,%eax # is it greater than 50? |
| 151 | movl $0,%eax |
| 152 | jle done # No, no need to normalize |
| 153 | |
| 154 | # Normalize by finding smallest metric and subtracting it |
| 155 | # from all metrics |
| 156 | movq (%edi),%mm0 |
| 157 | pminub 8(%edi),%mm0 |
| 158 | pminub 16(%edi),%mm0 |
| 159 | pminub 24(%edi),%mm0 |
| 160 | pminub 32(%edi),%mm0 |
| 161 | pminub 40(%edi),%mm0 |
| 162 | pminub 48(%edi),%mm0 |
| 163 | pminub 56(%edi),%mm0 |
| 164 | pminub 64(%edi),%mm0 |
| 165 | pminub 72(%edi),%mm0 |
| 166 | pminub 80(%edi),%mm0 |
| 167 | pminub 88(%edi),%mm0 |
| 168 | pminub 96(%edi),%mm0 |
| 169 | pminub 104(%edi),%mm0 |
| 170 | pminub 112(%edi),%mm0 |
| 171 | pminub 120(%edi),%mm0 |
| 172 | pminub 128(%edi),%mm0 |
| 173 | pminub 136(%edi),%mm0 |
| 174 | pminub 144(%edi),%mm0 |
| 175 | pminub 152(%edi),%mm0 |
| 176 | pminub 160(%edi),%mm0 |
| 177 | pminub 168(%edi),%mm0 |
| 178 | pminub 176(%edi),%mm0 |
| 179 | pminub 184(%edi),%mm0 |
| 180 | pminub 192(%edi),%mm0 |
| 181 | pminub 200(%edi),%mm0 |
| 182 | pminub 208(%edi),%mm0 |
| 183 | pminub 216(%edi),%mm0 |
| 184 | pminub 224(%edi),%mm0 |
| 185 | pminub 232(%edi),%mm0 |
| 186 | pminub 240(%edi),%mm0 |
| 187 | pminub 248(%edi),%mm0 |
| 188 | # mm0 contains 8 smallest metrics |
| 189 | # crunch down to single lowest metric |
| 190 | movq %mm0,%mm1 |
| 191 | psrlq $32,%mm0 |
| 192 | pminub %mm1,%mm0 |
| 193 | movq %mm0,%mm1 |
| 194 | psrlq $16,%mm0 |
| 195 | pminub %mm1,%mm0 |
| 196 | movq %mm0,%mm1 |
| 197 | psrlq $8,%mm0 |
| 198 | pminub %mm1,%mm0 |
| 199 | movq 8(%edi),%mm1 # reload |
| 200 | punpcklbw %mm0,%mm0 # expand to all 8 bytes |
| 201 | pshufw $0,%mm0,%mm0 |
| 202 | |
| 203 | # mm0 now contains lowest metric in all 8 bytes |
| 204 | # subtract it from every output metric |
| 205 | # Trashes %mm7 |
| 206 | .macro PSUBUSBM REG,MEM |
| 207 | movq \MEM,%mm7 |
| 208 | psubusb \REG,%mm7 |
| 209 | movq %mm7,\MEM |
| 210 | .endm |
| 211 | |
| 212 | PSUBUSBM %mm0,(%edi) |
| 213 | PSUBUSBM %mm0,8(%edi) |
| 214 | PSUBUSBM %mm0,16(%edi) |
| 215 | PSUBUSBM %mm0,24(%edi) |
| 216 | PSUBUSBM %mm0,32(%edi) |
| 217 | PSUBUSBM %mm0,40(%edi) |
| 218 | PSUBUSBM %mm0,48(%edi) |
| 219 | PSUBUSBM %mm0,56(%edi) |
| 220 | PSUBUSBM %mm0,64(%edi) |
| 221 | PSUBUSBM %mm0,72(%edi) |
| 222 | PSUBUSBM %mm0,80(%edi) |
| 223 | PSUBUSBM %mm0,88(%edi) |
| 224 | PSUBUSBM %mm0,96(%edi) |
| 225 | PSUBUSBM %mm0,104(%edi) |
| 226 | PSUBUSBM %mm0,112(%edi) |
| 227 | PSUBUSBM %mm0,120(%edi) |
| 228 | PSUBUSBM %mm0,128(%edi) |
| 229 | PSUBUSBM %mm0,136(%edi) |
| 230 | PSUBUSBM %mm0,144(%edi) |
| 231 | PSUBUSBM %mm0,152(%edi) |
| 232 | PSUBUSBM %mm0,160(%edi) |
| 233 | PSUBUSBM %mm0,168(%edi) |
| 234 | PSUBUSBM %mm0,176(%edi) |
| 235 | PSUBUSBM %mm0,184(%edi) |
| 236 | PSUBUSBM %mm0,192(%edi) |
| 237 | PSUBUSBM %mm0,200(%edi) |
| 238 | PSUBUSBM %mm0,208(%edi) |
| 239 | PSUBUSBM %mm0,216(%edi) |
| 240 | PSUBUSBM %mm0,224(%edi) |
| 241 | PSUBUSBM %mm0,232(%edi) |
| 242 | PSUBUSBM %mm0,240(%edi) |
| 243 | PSUBUSBM %mm0,248(%edi) |
| 244 | |
| 245 | done: |
| 246 | # swap metrics |
| 247 | movl %esi,%eax |
| 248 | movl %edi,%esi |
| 249 | movl %eax,%edi |
| 250 | jmp 1b |
| 251 | |
| 252 | 2: emms |
| 253 | movl 8(%ebp),%ebx # ebx = vp |
| 254 | # stash metric pointers |
| 255 | movl %esi,OLDMETRICS(%ebx) |
| 256 | movl %edi,NEWMETRICS(%ebx) |
| 257 | movl %edx,DP(%ebx) # stash incremented value of vp->dp |
| 258 | xorl %eax,%eax |
| 259 | err: popl %ebx |
| 260 | popl %edx |
| 261 | popl %edi |
| 262 | popl %esi |
| 263 | popl %ebp |
| 264 | ret |
| 265 | |
| 266 | .data |
| 267 | .align 8 |
| 268 | thirtyones: |
| 269 | .byte 31,31,31,31,31,31,31,31 |
| 270 | |
| 271 | |