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-rw-r--r--peakval_mmx_assist.s70
1 files changed, 70 insertions, 0 deletions
diff --git a/peakval_mmx_assist.s b/peakval_mmx_assist.s
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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_assist(signed short *in,int cnt);
+ .global peakval_mmx_assist
+ .type peakval_mmx_assist,@function
+ .align 16
+peakval_mmx_assist:
+ 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
+