255 lines
6.3 KiB
ArmAsm
255 lines
6.3 KiB
ArmAsm
/* Intel SIMD SSE2 implementation of Viterbi ACS butterflies
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for 256-state (k=9) 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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Modifications for x86_64, 2012 Matthias P. Braendli, HB9EGM
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- changed registers to x86-64 equivalents
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- changed instructions accordingly
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- %rip indirect addressing needed for position independent code,
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which is required because x86-64 needs dynamic libs to be PIC.
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That still doesn't work
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void update_viterbi29_blk_sse2(struct v29 *vp,unsigned char *syms,int nbits) ;
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*/
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# SSE2 (128-bit integer SIMD) version
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# All X86-64 CPUs include SSE2
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# These are offsets into struct v29, defined in viterbi29_av.c
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.set DP,512
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.set OLDMETRICS,516
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.set NEWMETRICS,520
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.text
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.global update_viterbi29_blk_sse2,Branchtab29_sse2
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.type update_viterbi29_blk_sse2,@function
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.align 16
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update_viterbi29_blk_sse2:
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pushq %rbp
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movq %rsp,%rbp
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/* convention different between i386 and x86_64: rsi and rdi belong to called function, not caller */
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/* Let's say we don't care (yet) */
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pushq %rsi
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pushq %rdi
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pushq %rdx
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pushq %rbx
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movq 8(%rbp),%rdx # edx = vp
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testq %rdx,%rdx
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jnz 0f
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movq -1,%rax
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jmp err
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0: movq OLDMETRICS(%rdx),%rsi # esi -> old metrics
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movq NEWMETRICS(%rdx),%rdi # edi -> new metrics
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movq DP(%rdx),%rdx # edx -> decisions
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1: movq 16(%rbp),%rax # eax = nbits
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decq %rax
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jl 2f # passed zero, we're done
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movq %rax,16(%rbp)
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xorq %rax,%rax
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movq 12(%rbp),%rbx # ebx = syms
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movb (%rbx),%al
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movd %rax,%xmm6 # xmm6[0] = first symbol
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movb 1(%rbx),%al
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movd %rax,%xmm5 # xmm5[0] = second symbol
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addq $2,%rbx
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movq %rbx,12(%rbp)
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punpcklbw %xmm6,%xmm6 # xmm6[1] = xmm6[0]
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punpcklbw %xmm5,%xmm5
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movdqa thirtyones(%rip),%xmm7
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pshuflw $0,%xmm6,%xmm6 # copy low word to low 3
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pshuflw $0,%xmm5,%xmm5
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punpcklqdq %xmm6,%xmm6 # propagate to all 16
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punpcklqdq %xmm5,%xmm5
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# xmm6 now contains first symbol in each byte, xmm5 the second
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movdqa thirtyones(%rip),%xmm7
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# each invocation of this macro does 16 butterflies in parallel
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.MACRO butterfly GROUP
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# compute branch metrics
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movdqa Branchtab29_sse2+(16*\GROUP)(%rip),%xmm4
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movdqa Branchtab29_sse2+128+(16*\GROUP)(%rip),%xmm3
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pxor %xmm6,%xmm4
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pxor %xmm5,%xmm3
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pavgb %xmm3,%xmm4
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psrlw $3,%xmm4
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pand %xmm7,%xmm4 # xmm4 contains branch metrics
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movdqa (16*\GROUP)(%esi),%xmm0 # Incoming path metric, high bit = 0
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movdqa ((16*\GROUP)+128)(%esi),%xmm3 # Incoming path metric, high bit = 1
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movdqa %xmm0,%xmm2
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movdqa %xmm3,%xmm1
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paddusb %xmm4,%xmm0
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paddusb %xmm4,%xmm3
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# invert branch metrics
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pxor %xmm7,%xmm4
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paddusb %xmm4,%xmm1
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paddusb %xmm4,%xmm2
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# Find survivors, leave in mm0,2
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pminub %xmm1,%xmm0
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pminub %xmm3,%xmm2
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# get decisions, leave in mm1,3
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pcmpeqb %xmm0,%xmm1
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pcmpeqb %xmm2,%xmm3
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# interleave and store new branch metrics in mm0,2
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movdqa %xmm0,%xmm4
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punpckhbw %xmm2,%xmm0 # interleave second 16 new metrics
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punpcklbw %xmm2,%xmm4 # interleave first 16 new metrics
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movdqa %xmm0,(32*\GROUP+16)(%rdi)
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movdqa %xmm4,(32*\GROUP)(%rdi)
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# interleave decisions & store
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movdqa %xmm1,%xmm4
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punpckhbw %xmm3,%xmm1
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punpcklbw %xmm3,%xmm4
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# work around bug in gas due to Intel doc error
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.byte 0x66,0x0f,0xd7,0xd9 # pmovmskb %xmm1,%ebx
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shlq $16,%rbx
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.byte 0x66,0x0f,0xd7,0xc4 # pmovmskb %xmm4,%eax
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orq %rax,%rbx
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movq %rbx,(4*\GROUP)(%rdx)
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.endm
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# invoke macro 8 times for a total of 128 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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butterfly GROUP=4
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butterfly GROUP=5
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butterfly GROUP=6
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butterfly GROUP=7
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addq $32,%rdx # bump decision pointer
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# see if we have to normalize
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movq (%rdi),%rax # extract first output metric
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andq $255,%rax
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cmp $50,%rax # is it greater than 50?
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movq $0,%rax
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jle done # No, no need to normalize
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# Normalize by finding smallest metric and subtracting it
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# from all metrics
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movdqa (%rdi),%xmm0
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pminub 16(%rdi),%xmm0
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pminub 32(%rdi),%xmm0
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pminub 48(%rdi),%xmm0
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pminub 64(%rdi),%xmm0
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pminub 80(%rdi),%xmm0
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pminub 96(%rdi),%xmm0
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pminub 112(%rdi),%xmm0
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pminub 128(%rdi),%xmm0
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pminub 144(%rdi),%xmm0
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pminub 160(%rdi),%xmm0
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pminub 176(%rdi),%xmm0
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pminub 192(%rdi),%xmm0
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pminub 208(%rdi),%xmm0
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pminub 224(%rdi),%xmm0
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pminub 240(%rdi),%xmm0
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# crunch down to single lowest metric
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movdqa %xmm0,%xmm1
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psrldq $8,%xmm0 # the count to psrldq is bytes, not bits!
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pminub %xmm1,%xmm0
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movdqa %xmm0,%xmm1
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psrlq $32,%xmm0
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pminub %xmm1,%xmm0
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movdqa %xmm0,%xmm1
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psrlq $16,%xmm0
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pminub %xmm1,%xmm0
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movdqa %xmm0,%xmm1
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psrlq $8,%xmm0
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pminub %xmm1,%xmm0
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punpcklbw %xmm0,%xmm0 # lowest 2 bytes
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pshuflw $0,%xmm0,%xmm0 # lowest 8 bytes
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punpcklqdq %xmm0,%xmm0 # all 16 bytes
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# xmm0 now contains lowest metric in all 16 bytes
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# subtract it from every output metric
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movdqa (%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,(%rdi)
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movdqa 16(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,16(%rdi)
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movdqa 32(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,32(%rdi)
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movdqa 48(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,48(%rdi)
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movdqa 64(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,64(%rdi)
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movdqa 80(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,80(%rdi)
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movdqa 96(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,96(%rdi)
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movdqa 112(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,112(%rdi)
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movdqa 128(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,128(%rdi)
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movdqa 144(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,144(%rdi)
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movdqa 160(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,160(%rdi)
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movdqa 176(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,176(%rdi)
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movdqa 192(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,192(%rdi)
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movdqa 208(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,208(%rdi)
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movdqa 224(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,224(%rdi)
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movdqa 240(%rdi),%xmm1
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psubusb %xmm0,%xmm1
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movdqa %xmm1,240(%rdi)
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done:
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# swap metrics
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movq %rsi,%rax
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movq %rdi,%rsi
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movq %rax,%rdi
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jmp 1b
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2: movq 8(%rbp),%rbx # ebx = vp
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# stash metric pointers
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movq %rsi,OLDMETRICS(%rbx)
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movq %rdi,NEWMETRICS(%rbx)
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movq %rdx,DP(%rbx) # stash incremented value of vp->dp
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xorq %rax,%rax
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err: popq %rbx
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popq %rdx
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popq %rdi
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popq %rsi
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popq %rbp
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ret
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.data
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.align 16
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thirtyones:
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.byte 31,31,31,31,31,31,31,31,31,31,31,31,31,31,31,31
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