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/* 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
.global update_viterbi29_blk_sse2,Branchtab29_sse2
.type update_viterbi29_blk_sse2,@function
.align 16
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)
# 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)
# 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
.align 16
.byte 31,31,31,31,31,31,31,31,31,31,31,31,31,31,31,31