aboutsummaryrefslogtreecommitdiffstats
path: root/dotprod_mmx_assist.s
diff options
context:
space:
mode:
Diffstat (limited to 'dotprod_mmx_assist.s')
-rw-r--r--dotprod_mmx_assist.s83
1 files changed, 83 insertions, 0 deletions
diff --git a/dotprod_mmx_assist.s b/dotprod_mmx_assist.s
new file mode 100644
index 0000000..25deffd
--- /dev/null
+++ b/dotprod_mmx_assist.s
@@ -0,0 +1,83 @@
+# SIMD MMX dot product
+# Equivalent to the following C code:
+# long dotprod(signed short *a,signed short *b,int cnt)
+# {
+# long sum = 0;
+# cnt *= 4;
+# while(cnt--)
+# sum += *a++ + *b++;
+# return sum;
+# }
+# a and b should also be 64-bit aligned, or speed will suffer greatly
+# Copyright 1999, Phil Karn KA9Q
+# May be used under the terms of the GNU Lesser General Public License (LGPL)
+
+ .text
+ .global dotprod_mmx_assist
+ .type dotprod_mmx_assist,@function
+dotprod_mmx_assist:
+ pushl %ebp
+ movl %esp,%ebp
+ pushl %esi
+ pushl %edi
+ pushl %ecx
+ pushl %ebx
+ movl 8(%ebp),%esi # a
+ movl 12(%ebp),%edi # b
+ movl 16(%ebp),%ecx # cnt
+ pxor %mm0,%mm0 # clear running sum (in two 32-bit halves)
+
+# MMX dot product loop unrolled 4 times, crunching 16 terms per loop
+ .align 16
+.Loop1: subl $4,%ecx
+ jl .Loop1Done
+
+ movq (%esi),%mm1 # mm1 = a[3],a[2],a[1],a[0]
+ pmaddwd (%edi),%mm1 # mm1 = b[3]*a[3]+b[2]*a[2],b[1]*a[1]+b[0]*a[0]
+ paddd %mm1,%mm0
+
+ movq 8(%esi),%mm1
+ pmaddwd 8(%edi),%mm1
+ paddd %mm1,%mm0
+
+ movq 16(%esi),%mm1
+ pmaddwd 16(%edi),%mm1
+ paddd %mm1,%mm0
+
+ movq 24(%esi),%mm1
+ addl $32,%esi
+ pmaddwd 24(%edi),%mm1
+ addl $32,%edi
+ paddd %mm1,%mm0
+
+ jmp .Loop1
+.Loop1Done:
+
+ addl $4,%ecx
+
+# MMX dot product loop, not unrolled, crunching 4 terms per loop
+# This could be redone as Duff's Device on the unrolled loop above
+.Loop2: subl $1,%ecx
+ jl .Loop2Done
+
+ movq (%esi),%mm1
+ addl $8,%esi
+ pmaddwd (%edi),%mm1
+ addl $8,%edi
+ paddd %mm1,%mm0
+ jmp .Loop2
+.Loop2Done:
+
+ movd %mm0,%ebx # right-hand word to ebx
+ punpckhdq %mm0,%mm0 # left-hand word to right side of %mm0
+ movd %mm0,%eax
+ addl %ebx,%eax # running sum now in %eax
+ emms # done with MMX
+
+ popl %ebx
+ popl %ecx
+ popl %edi
+ popl %esi
+ movl %ebp,%esp
+ popl %ebp
+ ret