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86 lines
1.6 KiB
86 lines
1.6 KiB
# SIMD SSE2 dot product
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# Equivalent to the following C code:
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# long dotprod(signed short *a,signed short *b,int cnt)
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# {
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# long sum = 0;
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# cnt *= 8;
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# while(cnt--)
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# sum += *a++ + *b++;
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# return sum;
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# }
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# a and b must be 128-bit aligned
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# Copyright 2001, Phil Karn KA9Q
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# May be used under the terms of the GNU Lesser General Public License (LGPL)
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.text
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.global dotprod_sse2_assist
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.type dotprod_sse2_assist,@function
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dotprod_sse2_assist:
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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 %ecx
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pushl %ebx
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movl 8(%ebp),%esi # a
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movl 12(%ebp),%edi # b
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movl 16(%ebp),%ecx # cnt
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pxor %xmm0,%xmm0 # clear running sum (in two 32-bit halves)
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# SSE2 dot product loop unrolled 4 times, crunching 32 terms per loop
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.align 16
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.Loop1: subl $4,%ecx
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jl .Loop1Done
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movdqa (%esi),%xmm1
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pmaddwd (%edi),%xmm1
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paddd %xmm1,%xmm0
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movdqa 16(%esi),%xmm1
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pmaddwd 16(%edi),%xmm1
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paddd %xmm1,%xmm0
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movdqa 32(%esi),%xmm1
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pmaddwd 32(%edi),%xmm1
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paddd %xmm1,%xmm0
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movdqa 48(%esi),%xmm1
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addl $64,%esi
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pmaddwd 48(%edi),%xmm1
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addl $64,%edi
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paddd %xmm1,%xmm0
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jmp .Loop1
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.Loop1Done:
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addl $4,%ecx
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# SSE2 dot product loop, not unrolled, crunching 4 terms per loop
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# This could be redone as Duff's Device on the unrolled loop above
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.Loop2: subl $1,%ecx
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jl .Loop2Done
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movdqa (%esi),%xmm1
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addl $16,%esi
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pmaddwd (%edi),%xmm1
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addl $16,%edi
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paddd %xmm1,%xmm0
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jmp .Loop2
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.Loop2Done:
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movdqa %xmm0,%xmm1
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psrldq $8,%xmm0
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paddd %xmm1,%xmm0
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movd %xmm0,%eax # right-hand word to eax
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psrldq $4,%xmm0
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movd %xmm0,%ebx
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addl %ebx,%eax
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popl %ebx
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popl %ecx
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popl %edi
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popl %esi
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movl %ebp,%esp
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popl %ebp
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ret
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