/* 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