firs.s.txt

一些纠错编码的c程序实现

/* 16-tap pipelined dot product for Pentium, equivalent to (but much faster
 * than) the C routine:
 *
 * float fir16(float a[16],float b[16])
 * {
 *	int i;
 *	float sum = 0;
 *	for(i=0;i<16;i++)
 *		sum += a[i]*b[i];
 *	return sum;
 * }
 *
 * Copyright 1996 Phil Karn, KA9Q	
 */
.globl _fir16
_fir16:
	pushl	%ebx

	movl	8(%esp),%eax	/* eax -> a[] */
	movl	12(%esp),%ebx	/* ebx -> b[] */

	flds	(%eax)
	fmuls	(%ebx)	/* a[0]*b[0] */
	flds	4(%eax)
	fmuls	4(%ebx)	/* a[1]*b[1]	a[0]*b[0] */
	flds	8(%eax)
	fmuls	8(%ebx)	/* a[2]*b[2]	a[1]*b[1]	a[0]*b[0] */
	fxch	%st(2)	/* a[0]*b[0]	a[1]*b[1]	a[2]*b[2] */
	faddp		/* sum0,1	a[2]*b[2] */
	flds	12(%eax)
	fmuls	12(%ebx)/* a[3]*b[3]	sum0,1		a[2]*b[2] */
	fxch	%st(2)	/* a[2]*b[2]	sum0,1		a[3]*b[3] */
	faddp		/* sum0,1,2	a[3]*b[3] */
	flds	16(%eax)
	fmuls	16(%ebx)
	fxch	%st(2)
	faddp
	flds	20(%eax)
	fmuls	20(%ebx)
	fxch	%st(2)
	faddp
	flds	24(%eax)
	fmuls	24(%ebx)
	fxch	%st(2)
	faddp
	flds	28(%eax)
	fmuls	28(%ebx)
	fxch	%st(2)
	faddp
	flds	32(%eax)
	fmuls	32(%ebx)
	fxch	%st(2)
	faddp
	flds	36(%eax)
	fmuls	36(%ebx)
	fxch	%st(2)
	faddp
	flds	40(%eax)
	fmuls	40(%ebx)
	fxch	%st(2)
	faddp
	flds	44(%eax)
	fmuls	44(%ebx)
	fxch	%st(2)
	faddp
	flds	48(%eax)
	fmuls	48(%ebx)
	fxch	%st(2)
	faddp
	flds	52(%eax)
	fmuls	52(%ebx)
	fxch	%st(2)
	faddp
	flds	56(%eax)
	fmuls	56(%ebx)
	fxch	%st(2)
	faddp
	flds	60(%eax)
	fmuls	60(%ebx)
	fxch	%st(2)
	faddp		/* sum		a[15]*b[15] */

	pop	%ebx

	faddp		/* sum left on stack */

	ret