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| /* Intel SIMD MMX implementation of Viterbi ACS butterflies
| for 64-state (k=7) convolutional code
| Copyright 2004 Phil Karn, KA9Q
| This code may be used under the terms of the GNU Lesser General Public License (LGPL)
|
| int update_viterbi27_blk_mmx(struct v27 *vp,unsigned char *syms,int nbits) ;
| */
| # MMX (64-bit SIMD) version
| # requires Pentium-MMX, Pentium-II or better
|
| # These are offsets into struct v27, defined in viterbi27_mmx.c
| .set DP,128
| .set OLDMETRICS,132
| .set NEWMETRICS,136
| .text
| .global update_viterbi27_blk_mmx,Mettab27_1,Mettab27_2
| .type update_viterbi27_blk_mmx,@function
| .align 16
|
| update_viterbi27_blk_mmx:
| 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)
|
| movl 12(%ebp),%ebx # ebx = syms
| movw (%ebx),%ax # ax = second symbol : first symbol
| addl $2,%ebx
| movl %ebx,12(%ebp)
|
| movb %ah,%bl
| andl $255,%eax
| andl $255,%ebx
|
| # shift into first array index dimension slot
| shll $5,%eax
| shll $5,%ebx
|
| # each invocation of this macro will do 8 butterflies in parallel
| .MACRO butterfly GROUP
| # Compute branch metrics
| movq (Mettab27_1+8*\GROUP)(%eax),%mm3
| movq fifteens,%mm0
|
| paddb (Mettab27_2+8*\GROUP)(%ebx),%mm3
| paddb ones,%mm3 # emulate pavgb - this may not be necessary
| psrlq $1,%mm3
| pand %mm0,%mm3
|
| movq (8*\GROUP)(%esi),%mm6 # Incoming path metric, high bit = 0
| movq ((8*\GROUP)+32)(%esi),%mm2 # Incoming path metric, high bit = 1
| movq %mm6,%mm1
| movq %mm2,%mm7
|
| paddb %mm3,%mm6
| paddb %mm3,%mm2
| pxor %mm0,%mm3 # invert branch metric
| paddb %mm3,%mm7 # path metric for inverted symbols
| paddb %mm3,%mm1
|
| # live registers 1 2 6 7
| # Compare mm6 and mm7; mm1 and mm2
| pxor %mm3,%mm3
| movq %mm6,%mm4
| movq %mm1,%mm5
| psubb %mm7,%mm4 # mm4 = mm6 - mm7
| psubb %mm2,%mm5 # mm5 = mm1 - mm2
| pcmpgtb %mm3,%mm4 # mm4 = first set of decisions (ff = 1 better)
| pcmpgtb %mm3,%mm5 # mm5 = second set of decisions
|
| # live registers 1 2 4 5 6 7
| # select survivors
| movq %mm4,%mm0
| pand %mm4,%mm7
| movq %mm5,%mm3
| pand %mm5,%mm2
| pandn %mm6,%mm0
| pandn %mm1,%mm3
| por %mm0,%mm7 # mm7 = first set of survivors
| por %mm3,%mm2 # mm2 = second set of survivors
|
| # live registers 2 4 5 7
| # interleave & store decisions in mm4, mm5
| # interleave & store new branch metrics in mm2, mm7
| movq %mm4,%mm3
| movq %mm7,%mm0
| punpckhbw %mm5,%mm4
| punpcklbw %mm5,%mm3
| punpcklbw %mm2,%mm7 # interleave second 8 new metrics
| punpckhbw %mm2,%mm0 # interleave first 8 new metrics
| movq %mm4,(16*\GROUP+8)(%edx)
| movq %mm3,(16*\GROUP)(%edx)
| movq %mm7,(16*\GROUP)(%edi)
| movq %mm0,(16*\GROUP+8)(%edi)
|
| .endm
|
| # invoke macro 4 times for a total of 32 butterflies
| butterfly GROUP=0
| butterfly GROUP=1
| butterfly GROUP=2
| butterfly GROUP=3
|
| addl $64,%edx # bump decision pointer
|
| # 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
| fifteens:
| .byte 15,15,15,15,15,15,15,15
|
| .align 8
| ones: .byte 1,1,1,1,1,1,1,1
|
|
