/src/opus/silk/Inlines.h

Source
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/*! \file silk_Inlines.h
 *  \brief silk_Inlines.h defines OPUS_INLINE signal processing functions.
 */

#ifndef SILK_FIX_INLINES_H
#define SILK_FIX_INLINES_H


/* count leading zeros of opus_int64 */
static OPUS_INLINE opus_int32 silk_CLZ64( opus_int64 in )
{
    opus_int32 in_upper;

    in_upper = (opus_int32)silk_RSHIFT64(in, 32);
    if (in_upper == 0) {
        /* Search in the lower 32 bits */
        return 32 + silk_CLZ32( (opus_int32) in );
    } else {
        /* Search in the upper 32 bits */
        return silk_CLZ32( in_upper );
    }
}

/* get number of leading zeros and fractional part (the bits right after the leading one */
static OPUS_INLINE void silk_CLZ_FRAC(
    opus_int32 in,            /* I  input                               */
    opus_int32 *lz,           /* O  number of leading zeros             */
    opus_int32 *frac_Q7       /* O  the 7 bits right after the leading one */
)
{
    opus_int32 lzeros = silk_CLZ32(in);

    * lz = lzeros;
    * frac_Q7 = silk_ROR32(in, 24 - lzeros) & 0x7f;
}

/* Approximation of square root                                          */
/* Accuracy: < +/- 10%  for output values > 15                           */
/*           < +/- 2.5% for output values > 120                          */
static OPUS_INLINE opus_int32 silk_SQRT_APPROX( opus_int32 x )
{
    opus_int32 y, lz, frac_Q7;

    if( x <= 0 ) {
        return 0;
    }

    silk_CLZ_FRAC(x, &lz, &frac_Q7);

    if( lz & 1 ) {
        y = 32768;
    } else {
        y = 46214;        /* 46214 = sqrt(2) * 32768 */
    }

    /* get scaling right */
    y >>= silk_RSHIFT(lz, 1);

    /* increment using fractional part of input */
    y = silk_SMLAWB(y, y, silk_SMULBB(213, frac_Q7));

    return y;
}

/* Divide two int32 values and return result as int32 in a given Q-domain */
static OPUS_INLINE opus_int32 silk_DIV32_varQ(   /* O    returns a good approximation of "(a32 << Qres) / b32" */
    const opus_int32     a32,               /* I    numerator (Q0)                  */
    const opus_int32     b32,               /* I    denominator (Q0)                */
    const opus_int       Qres               /* I    Q-domain of result (>= 0)       */
)
{
    opus_int   a_headrm, b_headrm, lshift;
    opus_int32 b32_inv, a32_nrm, b32_nrm, result;

    silk_assert( b32 != 0 );
    silk_assert( Qres >= 0 );

    /* Compute number of bits head room and normalize inputs */
    a_headrm = silk_CLZ32( silk_abs(a32) ) - 1;
    a32_nrm = silk_LSHIFT(a32, a_headrm);                                       /* Q: a_headrm                  */
    b_headrm = silk_CLZ32( silk_abs(b32) ) - 1;
    b32_nrm = silk_LSHIFT(b32, b_headrm);                                       /* Q: b_headrm                  */

    /* Inverse of b32, with 14 bits of precision */
    b32_inv = silk_DIV32_16( silk_int32_MAX >> 2, silk_RSHIFT(b32_nrm, 16) );   /* Q: 29 + 16 - b_headrm        */

    /* First approximation */
    result = silk_SMULWB(a32_nrm, b32_inv);                                     /* Q: 29 + a_headrm - b_headrm  */

    /* Compute residual by subtracting product of denominator and first approximation */
    /* It's OK to overflow because the final value of a32_nrm should always be small */
    a32_nrm = silk_SUB32_ovflw(a32_nrm, silk_LSHIFT_ovflw( silk_SMMUL(b32_nrm, result), 3 ));  /* Q: a_headrm   */

    /* Refinement */
    result = silk_SMLAWB(result, a32_nrm, b32_inv);                             /* Q: 29 + a_headrm - b_headrm  */

    /* Convert to Qres domain */
    lshift = 29 + a_headrm - b_headrm - Qres;
    if( lshift < 0 ) {
        return silk_LSHIFT_SAT32(result, -lshift);
    } else {
        if( lshift < 32){
            return silk_RSHIFT(result, lshift);
        } else {
            /* Avoid undefined result */
            return 0;
        }
    }
}

/* Invert int32 value and return result as int32 in a given Q-domain */
static OPUS_INLINE opus_int32 silk_INVERSE32_varQ(   /* O    returns a good approximation of "(1 << Qres) / b32" */
    const opus_int32     b32,                   /* I    denominator (Q0)                */
    const opus_int       Qres                   /* I    Q-domain of result (> 0)        */
)
{
    opus_int   b_headrm, lshift;
    opus_int32 b32_inv, b32_nrm, err_Q32, result;

    silk_assert( b32 != 0 );
    silk_assert( Qres > 0 );

    /* Compute number of bits head room and normalize input */
    b_headrm = silk_CLZ32( silk_abs(b32) ) - 1;
    b32_nrm = silk_LSHIFT(b32, b_headrm);                                       /* Q: b_headrm                */

    /* Inverse of b32, with 14 bits of precision */
    b32_inv = silk_DIV32_16( silk_int32_MAX >> 2, silk_RSHIFT(b32_nrm, 16) );   /* Q: 29 + 16 - b_headrm    */

    /* First approximation */
    result = silk_LSHIFT(b32_inv, 16);                                          /* Q: 61 - b_headrm            */

    /* Compute residual by subtracting product of denominator and first approximation from one */
    err_Q32 = silk_LSHIFT( ((opus_int32)1<<29) - silk_SMULWB(b32_nrm, b32_inv), 3 );        /* Q32                        */

    /* Refinement */
    result = silk_SMLAWW(result, err_Q32, b32_inv);                             /* Q: 61 - b_headrm            */

    /* Convert to Qres domain */
    lshift = 61 - b_headrm - Qres;
    if( lshift <= 0 ) {
        return silk_LSHIFT_SAT32(result, -lshift);
    } else {
        if( lshift < 32){
            return silk_RSHIFT(result, lshift);
        }else{
            /* Avoid undefined result */
            return 0;
        }
    }
}

#endif /* SILK_FIX_INLINES_H */

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Created: 2026-03-19 07:24