Inlines.h

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#ifndef SILK_FIX_INLINES_H
#define SILK_FIX_INLINES_H

#ifdef __cplusplus
extern "C"
{
#endif

/* 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;
 }
 }
}

#ifdef __cplusplus
}
#endif

#endif /* SILK_FIX_INLINES_H */