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/*=============================================================================
//
// This software has been released under the terms of the GNU Public
// license. See http://www.gnu.org/copyleft/gpl.html for details.
//
// Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
//
//=============================================================================
*/
#ifndef __FIR_H__
#define __FIR_H__
/* Fixpoint 16 bit fir filter FIR filter. The filter is implemented
both in C and MMX assembly. The filter consists of one macro
UPDATE_QUE and one inline function firn. The macro can be used for
adding new data to the circular buffer used by the filter firn.
Limitations: max length of n = 16*4 and n must be multiple of 4 (pad
fiter with zeros for other lengths). Sometimes it works with filters
longer than 4*16 (the problem is overshoot and the acumulated energy
in the filter taps). */
#ifdef HAVE_MMX
inline int32_t firn(int16_t* x, int16_t* w, int16_t n)
{
register int32_t y; // Output
// Prologue
asm volatile(" pxor %mm1, %mm1;\n" ); // Clear buffer yt
// Main loop
while((n-=4)>=0){
asm volatile(
" movq (%1), %%mm0;\n" // Load x(n:n+4)
" pmaddwd (%0), %%mm0;\n" // yt(n:n+1)=sum(x(n:n+4).*w(n:n+4))
" psrld $16, %%mm0;\n" // yt(n:n+1)=yt(n:n+1)>>16
" paddd %%mm0, %%mm1;\n" // yt(n:n+1)=yt(n-2:n-1)+yt(n:n+1)
:: "r" (w), "r" (x));
w+=4; x+=4;
}
// Epilogue
asm volatile(
" movq %%mm1, %%mm0;\n"
" punpckhdq %%mm1, %%mm0;\n"
" paddd %%mm0, %%mm1;\n" //yt(n)=yt(n)+yt(n+1)
" movd %%mm1, %0 ;\n" //y=yt
" emms ;\n"
: "=&r" (y));
return y;
}
#else /* HAVE_MMX */
// Same thing as above but in C
inline int32_t firn(int16_t* x, int16_t* w, int16_t n)
{
register int32_t y=0;
while((n-=4) >=0)
y+=w[n]*x[n]+w[n+1]*x[n+1]+w[n+2]*x[n+2]+w[n+3]*x[n+3] >> 16;
return y;
}
#endif /* HAVE_MMX */
// Macro to add new data to circular queue
#define UPDATE_QUE(ind,xq,xid) \
xid=(--xid)&(L-1); \
xq[xid]=xq[xid+L]=*(ind);
#ifdef L8
#ifdef HAVE_MMX
#define FIR(x,w,y) *y=(int16_t)firn(x,w,8);
#else /* HAVE_MMX */
// Unrolled loop to speed up execution
#define FIR(x,w,y){ \
int16_t a = (w[0]*x[0]+w[1]*x[1]+w[2]*x[2]+w[3]*x[3]) >> 16; \
int16_t b = (w[4]*x[4]+w[5]*x[5]+w[6]*x[6]+w[7]*x[7]) >> 16; \
y[0] = a+b; \
}
#endif /* HAVE_MMX */
#endif /* L8 */
#ifdef L16
#define FIR(x,w,y) *y=(int16_t)firn(x,w,16);
#endif /* L16 */
#endif /* __FIR_H__ */
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