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| # MMX assist routines for peakval
| # Copyright 2001 Phil Karn, KA9Q
| # May be used under the terms of the GNU Lesser General Public License (LGPL)
|
| .text
|
| # Find peak value in signed 16-bit input samples
| # int peakval_mmx(signed short *in,int cnt);
| .global peakval_mmx
| .type peakval_mmx,@function
| .align 16
| peakval_mmx:
| pushl %ebp
| movl %esp,%ebp
| pushl %esi
| pushl %ecx
| pushl %ebx
|
| movl 8(%ebp),%esi
| movl 12(%ebp),%ecx
|
| pxor %mm7,%mm7 # clear peak
|
| 1: subl $4,%ecx
| jl 2f
| movq (%esi),%mm0
| movq %mm0,%mm1
| psraw $15,%mm1 # mm1 = 1's if negative, 0's if positive
| pxor %mm1,%mm0 # complement negatives
| psubw %mm1,%mm0 # add 1 to negatives
| movq %mm7,%mm6 # copy previous peak
| pcmpgtw %mm0,%mm6 # ff == old peak greater
| pand %mm6,%mm7 # select old peaks that are greater
| pandn %mm0,%mm6 # select new values that are greater
| por %mm6,%mm7
|
| addl $8,%esi
| jmp 1b
|
| 2: movd %mm7,%eax
| psrlq $16,%mm7
| andl $0xffff,%eax
|
| movd %mm7,%edx
| psrlq $16,%mm7
| andl $0xffff,%edx
| cmpl %edx,%eax
| jnl 3f
| movl %edx,%eax
| 3:
| movd %mm7,%edx
| psrlq $16,%mm7
| andl $0xffff,%edx
| cmpl %edx,%eax
| jnl 4f
| movl %edx,%eax
| 4:
| movd %mm7,%edx
| andl $0xffff,%edx
| cmpl %edx,%eax
| jnl 5f
| movl %edx,%eax
| 5:
| emms
| popl %ebx
| popl %ecx
| popl %esi
| popl %ebp
| ret
|
|
|
