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