/* Intel SIMD SSE 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_sse(struct v29 *vp,unsigned char syms[],int nbits); */ # SSE (64-bit integer SIMD) version # Requires Pentium III 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_sse,Branchtab29_sse .type update_viterbi29_blk_sse,@function .align 16 update_viterbi29_blk_sse: 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,%mm6 # mm6[0] = first symbol movb 1(%ebx),%al movd %eax,%mm5 # mm5[0] = second symbol addl $2,%ebx movl %ebx,12(%ebp) punpcklbw %mm6,%mm6 # mm6[1] = mm6[0] punpcklbw %mm5,%mm5 movq thirtyones,%mm7 pshufw $0,%mm6,%mm6 # copy low word to upper 3 pshufw $0,%mm5,%mm5 # mm6 now contains first symbol in each byte, mm5 the second # each invocation of this macro does 8 butterflies in parallel .MACRO butterfly GROUP # compute branch metrics movq Branchtab29_sse+(8*\GROUP),%mm4 movq Branchtab29_sse+128+(8*\GROUP),%mm3 pxor %mm6,%mm4 pxor %mm5,%mm3 pavgb %mm3,%mm4 # mm4 contains branch metrics psrlw $3,%mm4 pand %mm7,%mm4 movq (8*\GROUP)(%esi),%mm0 # Incoming path metric, high bit = 0 movq ((8*\GROUP)+128)(%esi),%mm3 # Incoming path metric, high bit = 1 movq %mm0,%mm2 movq %mm3,%mm1 paddusb %mm4,%mm0 paddusb %mm4,%mm3 # invert branch metrics. This works only because they're 5 bits pxor %mm7,%mm4 paddusb %mm4,%mm1 paddusb %mm4,%mm2 # Find survivors, leave in mm0,2 pminub %mm1,%mm0 pminub %mm3,%mm2 # get decisions, leave in mm1,3 pcmpeqb %mm0,%mm1 pcmpeqb %mm2,%mm3 # interleave and store new branch metrics in mm0,2 movq %mm0,%mm4 punpckhbw %mm2,%mm0 # interleave second 8 new metrics punpcklbw %mm2,%mm4 # interleave first 8 new metrics movq %mm0,(16*\GROUP+8)(%edi) movq %mm4,(16*\GROUP)(%edi) # interleave decisions, accumulate into %ebx movq %mm1,%mm4 punpckhbw %mm3,%mm1 punpcklbw %mm3,%mm4 # Due to an error in the Intel instruction set ref (the register # fields are swapped), gas assembles pmovmskb incorrectly # See http://mail.gnu.org/pipermail/bug-gnu-utils/2000-August/002341.html .byte 0x0f,0xd7,0xc1 # pmovmskb %mm1,%eax shll $((16*\GROUP+8)&31),%eax orl %eax,%ebx .byte 0x0f,0xd7,0xc4 # pmovmskb %mm4,%eax shll $((16*\GROUP)&31),%eax orl %eax,%ebx .endm # invoke macro 16 times for a total of 128 butterflies xorl %ebx,%ebx # clear decisions butterfly GROUP=0 butterfly GROUP=1 movl %ebx,(%edx) # stash first 32 decisions xorl %ebx,%ebx butterfly GROUP=2 butterfly GROUP=3 movl %ebx,4(%edx) # stash second 32 decisions xorl %ebx,%ebx # clear decisions butterfly GROUP=4 butterfly GROUP=5 movl %ebx,8(%edx) # stash first 32 decisions xorl %ebx,%ebx butterfly GROUP=6 butterfly GROUP=7 movl %ebx,12(%edx) # stash second 32 decisions xorl %ebx,%ebx # clear decisions butterfly GROUP=8 butterfly GROUP=9 movl %ebx,16(%edx) # stash first 32 decisions xorl %ebx,%ebx butterfly GROUP=10 butterfly GROUP=11 movl %ebx,20(%edx) # stash second 32 decisions xorl %ebx,%ebx # clear decisions butterfly GROUP=12 butterfly GROUP=13 movl %ebx,24(%edx) # stash first 32 decisions xorl %ebx,%ebx butterfly GROUP=14 butterfly GROUP=15 movl %ebx,28(%edx) # stash second 32 decisions 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 movq (%edi),%mm0 pminub 8(%edi),%mm0 pminub 16(%edi),%mm0 pminub 24(%edi),%mm0 pminub 32(%edi),%mm0 pminub 40(%edi),%mm0 pminub 48(%edi),%mm0 pminub 56(%edi),%mm0 pminub 64(%edi),%mm0 pminub 72(%edi),%mm0 pminub 80(%edi),%mm0 pminub 88(%edi),%mm0 pminub 96(%edi),%mm0 pminub 104(%edi),%mm0 pminub 112(%edi),%mm0 pminub 120(%edi),%mm0 pminub 128(%edi),%mm0 pminub 136(%edi),%mm0 pminub 144(%edi),%mm0 pminub 152(%edi),%mm0 pminub 160(%edi),%mm0 pminub 168(%edi),%mm0 pminub 176(%edi),%mm0 pminub 184(%edi),%mm0 pminub 192(%edi),%mm0 pminub 200(%edi),%mm0 pminub 208(%edi),%mm0 pminub 216(%edi),%mm0 pminub 224(%edi),%mm0 pminub 232(%edi),%mm0 pminub 240(%edi),%mm0 pminub 248(%edi),%mm0 # mm0 contains 8 smallest metrics # crunch down to single lowest metric movq %mm0,%mm1 psrlq $32,%mm0 pminub %mm1,%mm0 movq %mm0,%mm1 psrlq $16,%mm0 pminub %mm1,%mm0 movq %mm0,%mm1 psrlq $8,%mm0 pminub %mm1,%mm0 movq 8(%edi),%mm1 # reload punpcklbw %mm0,%mm0 # expand to all 8 bytes pshufw $0,%mm0,%mm0 # mm0 now contains lowest metric in all 8 bytes # subtract it from every output metric # Trashes %mm7 .macro PSUBUSBM REG,MEM movq \MEM,%mm7 psubusb \REG,%mm7 movq %mm7,\MEM .endm PSUBUSBM %mm0,(%edi) PSUBUSBM %mm0,8(%edi) PSUBUSBM %mm0,16(%edi) PSUBUSBM %mm0,24(%edi) PSUBUSBM %mm0,32(%edi) PSUBUSBM %mm0,40(%edi) PSUBUSBM %mm0,48(%edi) PSUBUSBM %mm0,56(%edi) PSUBUSBM %mm0,64(%edi) PSUBUSBM %mm0,72(%edi) PSUBUSBM %mm0,80(%edi) PSUBUSBM %mm0,88(%edi) PSUBUSBM %mm0,96(%edi) PSUBUSBM %mm0,104(%edi) PSUBUSBM %mm0,112(%edi) PSUBUSBM %mm0,120(%edi) PSUBUSBM %mm0,128(%edi) PSUBUSBM %mm0,136(%edi) PSUBUSBM %mm0,144(%edi) PSUBUSBM %mm0,152(%edi) PSUBUSBM %mm0,160(%edi) PSUBUSBM %mm0,168(%edi) PSUBUSBM %mm0,176(%edi) PSUBUSBM %mm0,184(%edi) PSUBUSBM %mm0,192(%edi) PSUBUSBM %mm0,200(%edi) PSUBUSBM %mm0,208(%edi) PSUBUSBM %mm0,216(%edi) PSUBUSBM %mm0,224(%edi) PSUBUSBM %mm0,232(%edi) PSUBUSBM %mm0,240(%edi) PSUBUSBM %mm0,248(%edi) done: # swap metrics movl %esi,%eax movl %edi,%esi movl %eax,%edi jmp 1b 2: emms 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 8 thirtyones: .byte 31,31,31,31,31,31,31,31