diff options
Diffstat (limited to 'sse2bfly29-64.s')
| -rw-r--r-- | sse2bfly29-64.s | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/sse2bfly29-64.s b/sse2bfly29-64.s new file mode 100644 index 0000000..22bd8a1 --- /dev/null +++ b/sse2bfly29-64.s @@ -0,0 +1,254 @@ +/* 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) + + Modifications for x86_64, 2012 Matthias P. Braendli, HB9EGM + - changed registers to x86-64 equivalents + - changed instructions accordingly + - %rip indirect addressing needed for position independent code, + which is required because x86-64 needs dynamic libs to be PIC. + That still doesn't work + + void update_viterbi29_blk_sse2(struct v29 *vp,unsigned char *syms,int nbits) ; +*/ + # SSE2 (128-bit integer SIMD) version + # All X86-64 CPUs include SSE2 + + # These are offsets into struct v29, defined in viterbi29_av.c + .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: + pushq %rbp + movq %rsp,%rbp + /* convention different between i386 and x86_64: rsi and rdi belong to called function, not caller */ + /* Let's say we don't care (yet) */ + pushq %rsi + pushq %rdi + pushq %rdx + pushq %rbx + + movq 8(%rbp),%rdx # edx = vp + testq %rdx,%rdx + jnz 0f + movq -1,%rax + jmp err +0: movq OLDMETRICS(%rdx),%rsi # esi -> old metrics + movq NEWMETRICS(%rdx),%rdi # edi -> new metrics + movq DP(%rdx),%rdx # edx -> decisions + +1: movq 16(%rbp),%rax # eax = nbits + decq %rax + jl 2f # passed zero, we're done + movq %rax,16(%rbp) + + xorq %rax,%rax + movq 12(%rbp),%rbx # ebx = syms + movb (%rbx),%al + movd %rax,%xmm6 # xmm6[0] = first symbol + movb 1(%rbx),%al + movd %rax,%xmm5 # xmm5[0] = second symbol + addq $2,%rbx + movq %rbx,12(%rbp) + + punpcklbw %xmm6,%xmm6 # xmm6[1] = xmm6[0] + punpcklbw %xmm5,%xmm5 + movdqa thirtyones(%rip),%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(%rip),%xmm7 + + # each invocation of this macro does 16 butterflies in parallel + .MACRO butterfly GROUP + # compute branch metrics + movdqa Branchtab29_sse2+(16*\GROUP)(%rip),%xmm4 + movdqa Branchtab29_sse2+128+(16*\GROUP)(%rip),%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)(%rdi) + movdqa %xmm4,(32*\GROUP)(%rdi) + + # 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 + shlq $16,%rbx + .byte 0x66,0x0f,0xd7,0xc4 # pmovmskb %xmm4,%eax + orq %rax,%rbx + movq %rbx,(4*\GROUP)(%rdx) + .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 + + addq $32,%rdx # bump decision pointer + + # see if we have to normalize + movq (%rdi),%rax # extract first output metric + andq $255,%rax + cmp $50,%rax # is it greater than 50? + movq $0,%rax + jle done # No, no need to normalize + + # Normalize by finding smallest metric and subtracting it + # from all metrics + movdqa (%rdi),%xmm0 + pminub 16(%rdi),%xmm0 + pminub 32(%rdi),%xmm0 + pminub 48(%rdi),%xmm0 + pminub 64(%rdi),%xmm0 + pminub 80(%rdi),%xmm0 + pminub 96(%rdi),%xmm0 + pminub 112(%rdi),%xmm0 + pminub 128(%rdi),%xmm0 + pminub 144(%rdi),%xmm0 + pminub 160(%rdi),%xmm0 + pminub 176(%rdi),%xmm0 + pminub 192(%rdi),%xmm0 + pminub 208(%rdi),%xmm0 + pminub 224(%rdi),%xmm0 + pminub 240(%rdi),%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 (%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,(%rdi) + movdqa 16(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,16(%rdi) + movdqa 32(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,32(%rdi) + movdqa 48(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,48(%rdi) + movdqa 64(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,64(%rdi) + movdqa 80(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,80(%rdi) + movdqa 96(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,96(%rdi) + movdqa 112(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,112(%rdi) + movdqa 128(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,128(%rdi) + movdqa 144(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,144(%rdi) + movdqa 160(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,160(%rdi) + movdqa 176(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,176(%rdi) + movdqa 192(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,192(%rdi) + movdqa 208(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,208(%rdi) + movdqa 224(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,224(%rdi) + movdqa 240(%rdi),%xmm1 + psubusb %xmm0,%xmm1 + movdqa %xmm1,240(%rdi) + +done: + # swap metrics + movq %rsi,%rax + movq %rdi,%rsi + movq %rax,%rdi + jmp 1b + +2: movq 8(%rbp),%rbx # ebx = vp + # stash metric pointers + movq %rsi,OLDMETRICS(%rbx) + movq %rdi,NEWMETRICS(%rbx) + movq %rdx,DP(%rbx) # stash incremented value of vp->dp + xorq %rax,%rax +err: popq %rbx + popq %rdx + popq %rdi + popq %rsi + popq %rbp + ret + + .data + .align 16 +thirtyones: + .byte 31,31,31,31,31,31,31,31,31,31,31,31,31,31,31,31 + |