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#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <arm_neon.h>
#include "SigProc_FIX.h"
#include "define.h"

#define QA                          24
#define A_LIMIT                     SILK_FIX_CONST( 0.99975, QA )

#define MUL32_FRAC_Q(a32, b32, Q)   ((opus_int32)(silk_RSHIFT_ROUND64(silk_SMULL(a32, b32), Q)))

/* The difficulty is how to judge a 64-bit signed integer tmp64 is 32-bit overflowed,
 * since NEON has no 64-bit min, max or comparison instructions.
 * A failed idea is to compare the results of vmovn(tmp64) and vqmovn(tmp64) whether they are equal or not.
 * However, this idea fails when the tmp64 is something like 0xFFFFFFF980000000.
 * Here we know that mult2Q >= 1, so the highest bit (bit 63, sign bit) of tmp64 must equal to bit 62.
 * tmp64 was shifted left by 1 and we got tmp64'. If high_half(tmp64') != 0 and high_half(tmp64') != -1,
 * then we know that bit 31 to bit 63 of tmp64 can not all be the sign bit, and therefore tmp64 is 32-bit overflowed.
 * That is, we judge if tmp64' > 0x00000000FFFFFFFF, or tmp64' <= 0xFFFFFFFF00000000.
 * We use narrowing shift right 31 bits to tmp32' to save data bandwidth and instructions.
 * That is, we judge if tmp32' > 0x00000000, or tmp32' <= 0xFFFFFFFF.
 */

/* Compute inverse of LPC prediction gain, and                          */
/* test if LPC coefficients are stable (all poles within unit circle)   */
static OPUS_INLINE opus_int32 LPC_inverse_pred_gain_QA_neon( /* O   Returns inverse prediction gain in energy domain, Q30    */
    opus_int32           A_QA[ SILK_MAX_ORDER_LPC ],         /* I   Prediction coefficients                                  */
    const opus_int       order                               /* I   Prediction order                                         */
)
{
    opus_int   k, n, mult2Q;
    opus_int32 invGain_Q30, rc_Q31, rc_mult1_Q30, rc_mult2, tmp1, tmp2;
    opus_int32 max, min;
    int32x4_t  max_s32x4, min_s32x4;
    int32x2_t  max_s32x2, min_s32x2;

    max_s32x4 = vdupq_n_s32( silk_int32_MIN );
    min_s32x4 = vdupq_n_s32( silk_int32_MAX );
    invGain_Q30 = SILK_FIX_CONST( 1, 30 );
    for( k = order - 1; k > 0; k-- ) {
        int32x2_t rc_Q31_s32x2, rc_mult2_s32x2;
        int64x2_t mult2Q_s64x2;

        /* Check for stability */
        if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {
            return 0;
        }

        /* Set RC equal to negated AR coef */
        rc_Q31 = -silk_LSHIFT( A_QA[ k ], 31 - QA );

        /* rc_mult1_Q30 range: [ 1 : 2^30 ] */
        rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );
        silk_assert( rc_mult1_Q30 > ( 1 << 15 ) );                   /* reduce A_LIMIT if fails */
        silk_assert( rc_mult1_Q30 <= ( 1 << 30 ) );

        /* Update inverse gain */
        /* invGain_Q30 range: [ 0 : 2^30 ] */
        invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
        silk_assert( invGain_Q30 >= 0           );
        silk_assert( invGain_Q30 <= ( 1 << 30 ) );
        if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {
            return 0;
        }

        /* rc_mult2 range: [ 2^30 : silk_int32_MAX ] */
        mult2Q = 32 - silk_CLZ32( silk_abs( rc_mult1_Q30 ) );
        rc_mult2 = silk_INVERSE32_varQ( rc_mult1_Q30, mult2Q + 30 );

        /* Update AR coefficient */
        rc_Q31_s32x2   = vdup_n_s32( rc_Q31 );
        mult2Q_s64x2   = vdupq_n_s64( -mult2Q );
        rc_mult2_s32x2 = vdup_n_s32( rc_mult2 );

        for( n = 0; n < ( ( k + 1 ) >> 1 ) - 3; n += 4 ) {
            /* We always calculate extra elements of A_QA buffer when ( k % 4 ) != 0, to take the advantage of SIMD parallelization. */
            int32x4_t tmp1_s32x4, tmp2_s32x4, t0_s32x4, t1_s32x4, s0_s32x4, s1_s32x4, t_QA0_s32x4, t_QA1_s32x4;
            int64x2_t t0_s64x2, t1_s64x2, t2_s64x2, t3_s64x2;
            tmp1_s32x4  = vld1q_s32( A_QA + n );
            tmp2_s32x4  = vld1q_s32( A_QA + k - n - 4 );
            tmp2_s32x4  = vrev64q_s32( tmp2_s32x4 );
            tmp2_s32x4  = vcombine_s32( vget_high_s32( tmp2_s32x4 ), vget_low_s32( tmp2_s32x4 ) );
            t0_s32x4    = vqrdmulhq_lane_s32( tmp2_s32x4, rc_Q31_s32x2, 0 );
            t1_s32x4    = vqrdmulhq_lane_s32( tmp1_s32x4, rc_Q31_s32x2, 0 );
            t_QA0_s32x4 = vqsubq_s32( tmp1_s32x4, t0_s32x4 );
            t_QA1_s32x4 = vqsubq_s32( tmp2_s32x4, t1_s32x4 );
            t0_s64x2    = vmull_s32( vget_low_s32 ( t_QA0_s32x4 ), rc_mult2_s32x2 );
            t1_s64x2    = vmull_s32( vget_high_s32( t_QA0_s32x4 ), rc_mult2_s32x2 );
            t2_s64x2    = vmull_s32( vget_low_s32 ( t_QA1_s32x4 ), rc_mult2_s32x2 );
            t3_s64x2    = vmull_s32( vget_high_s32( t_QA1_s32x4 ), rc_mult2_s32x2 );
            t0_s64x2    = vrshlq_s64( t0_s64x2, mult2Q_s64x2 );
            t1_s64x2    = vrshlq_s64( t1_s64x2, mult2Q_s64x2 );
            t2_s64x2    = vrshlq_s64( t2_s64x2, mult2Q_s64x2 );
            t3_s64x2    = vrshlq_s64( t3_s64x2, mult2Q_s64x2 );
            t0_s32x4    = vcombine_s32( vmovn_s64( t0_s64x2 ), vmovn_s64( t1_s64x2 ) );
            t1_s32x4    = vcombine_s32( vmovn_s64( t2_s64x2 ), vmovn_s64( t3_s64x2 ) );
            s0_s32x4    = vcombine_s32( vshrn_n_s64( t0_s64x2, 31 ), vshrn_n_s64( t1_s64x2, 31 ) );
            s1_s32x4    = vcombine_s32( vshrn_n_s64( t2_s64x2, 31 ), vshrn_n_s64( t3_s64x2, 31 ) );
            max_s32x4   = vmaxq_s32( max_s32x4, s0_s32x4 );
            min_s32x4   = vminq_s32( min_s32x4, s0_s32x4 );
            max_s32x4   = vmaxq_s32( max_s32x4, s1_s32x4 );
            min_s32x4   = vminq_s32( min_s32x4, s1_s32x4 );
            t1_s32x4    = vrev64q_s32( t1_s32x4 );
            t1_s32x4    = vcombine_s32( vget_high_s32( t1_s32x4 ), vget_low_s32( t1_s32x4 ) );
            vst1q_s32( A_QA + n,         t0_s32x4 );
            vst1q_s32( A_QA + k - n - 4, t1_s32x4 );
        }
        for( ; n < (k + 1) >> 1; n++ ) {
            opus_int64 tmp64;
            tmp1 = A_QA[ n ];
            tmp2 = A_QA[ k - n - 1 ];
            tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp1,
                  MUL32_FRAC_Q( tmp2, rc_Q31, 31 ) ), rc_mult2 ), mult2Q);
            if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {
               return 0;
            }
            A_QA[ n ] = ( opus_int32 )tmp64;
            tmp64 = silk_RSHIFT_ROUND64( silk_SMULL( silk_SUB_SAT32(tmp2,
                  MUL32_FRAC_Q( tmp1, rc_Q31, 31 ) ), rc_mult2), mult2Q);
            if( tmp64 > silk_int32_MAX || tmp64 < silk_int32_MIN ) {
               return 0;
            }
            A_QA[ k - n - 1 ] = ( opus_int32 )tmp64;
        }
    }

    /* Check for stability */
    if( ( A_QA[ k ] > A_LIMIT ) || ( A_QA[ k ] < -A_LIMIT ) ) {
        return 0;
    }

    max_s32x2 = vmax_s32( vget_low_s32( max_s32x4 ), vget_high_s32( max_s32x4 ) );
    min_s32x2 = vmin_s32( vget_low_s32( min_s32x4 ), vget_high_s32( min_s32x4 ) );
    max_s32x2 = vmax_s32( max_s32x2, vreinterpret_s32_s64( vshr_n_s64( vreinterpret_s64_s32( max_s32x2 ), 32 ) ) );
    min_s32x2 = vmin_s32( min_s32x2, vreinterpret_s32_s64( vshr_n_s64( vreinterpret_s64_s32( min_s32x2 ), 32 ) ) );
    max = vget_lane_s32( max_s32x2, 0 );
    min = vget_lane_s32( min_s32x2, 0 );
    if( ( max > 0 ) || ( min < -1 ) ) {
        return 0;
    }

    /* Set RC equal to negated AR coef */
    rc_Q31 = -silk_LSHIFT( A_QA[ 0 ], 31 - QA );

    /* Range: [ 1 : 2^30 ] */
    rc_mult1_Q30 = silk_SUB32( SILK_FIX_CONST( 1, 30 ), silk_SMMUL( rc_Q31, rc_Q31 ) );

    /* Update inverse gain */
    /* Range: [ 0 : 2^30 ] */
    invGain_Q30 = silk_LSHIFT( silk_SMMUL( invGain_Q30, rc_mult1_Q30 ), 2 );
    silk_assert( invGain_Q30 >= 0           );
    silk_assert( invGain_Q30 <= ( 1 << 30 ) );
    if( invGain_Q30 < SILK_FIX_CONST( 1.0f / MAX_PREDICTION_POWER_GAIN, 30 ) ) {
        return 0;
    }

    return invGain_Q30;
}

/* For input in Q12 domain */
opus_int32 silk_LPC_inverse_pred_gain_neon(         /* O   Returns inverse prediction gain in energy domain, Q30        */
    const opus_int16            *A_Q12,             /* I   Prediction coefficients, Q12 [order]                         */
    const opus_int              order               /* I   Prediction order                                             */
)
{
#ifdef OPUS_CHECK_ASM
    const opus_int32 invGain_Q30_c = silk_LPC_inverse_pred_gain_c( A_Q12, order );
#endif

    opus_int32 invGain_Q30;
    if( ( SILK_MAX_ORDER_LPC != 24 ) || ( order & 1 )) {
        invGain_Q30 = silk_LPC_inverse_pred_gain_c( A_Q12, order );
    }
    else {
        opus_int32 Atmp_QA[ SILK_MAX_ORDER_LPC ];
        opus_int32 DC_resp;
        int16x8_t  t0_s16x8, t1_s16x8, t2_s16x8;
        int32x4_t  t0_s32x4;
        const opus_int leftover = order & 7;

        /* Increase Q domain of the AR coefficients */
        t0_s16x8 = vld1q_s16( A_Q12 +  0 );
        t1_s16x8 = vld1q_s16( A_Q12 +  8 );
        t2_s16x8 = vld1q_s16( A_Q12 + 16 );
        t0_s32x4 = vpaddlq_s16( t0_s16x8 );

        switch( order - leftover )
        {
        case 24:
            t0_s32x4 = vpadalq_s16( t0_s32x4, t2_s16x8 );
            /* FALLTHROUGH */

        case 16:
            t0_s32x4 = vpadalq_s16( t0_s32x4, t1_s16x8 );
            vst1q_s32( Atmp_QA + 16, vshll_n_s16( vget_low_s16 ( t2_s16x8 ), QA - 12 ) );
            vst1q_s32( Atmp_QA + 20, vshll_n_s16( vget_high_s16( t2_s16x8 ), QA - 12 ) );
            /* FALLTHROUGH */

        case 8:
        {
            const int32x2_t t_s32x2 = vpadd_s32( vget_low_s32( t0_s32x4 ), vget_high_s32( t0_s32x4 ) );
            const int64x1_t t_s64x1 = vpaddl_s32( t_s32x2 );
            DC_resp = vget_lane_s32( vreinterpret_s32_s64( t_s64x1 ), 0 );
            vst1q_s32( Atmp_QA +  8, vshll_n_s16( vget_low_s16 ( t1_s16x8 ), QA - 12 ) );
            vst1q_s32( Atmp_QA + 12, vshll_n_s16( vget_high_s16( t1_s16x8 ), QA - 12 ) );
        }
        break;

        default:
            DC_resp = 0;
            break;
        }
        A_Q12 += order - leftover;

        switch( leftover )
        {
        case 6:
            DC_resp += (opus_int32)A_Q12[ 5 ];
            DC_resp += (opus_int32)A_Q12[ 4 ];
            /* FALLTHROUGH */

        case 4:
            DC_resp += (opus_int32)A_Q12[ 3 ];
            DC_resp += (opus_int32)A_Q12[ 2 ];
            /* FALLTHROUGH */

        case 2:
            DC_resp += (opus_int32)A_Q12[ 1 ];
            DC_resp += (opus_int32)A_Q12[ 0 ];
            /* FALLTHROUGH */

        default:
            break;
        }

        /* If the DC is unstable, we don't even need to do the full calculations */
        if( DC_resp >= 4096 ) {
            invGain_Q30 = 0;
        } else {
            vst1q_s32( Atmp_QA + 0, vshll_n_s16( vget_low_s16 ( t0_s16x8 ), QA - 12 ) );
            vst1q_s32( Atmp_QA + 4, vshll_n_s16( vget_high_s16( t0_s16x8 ), QA - 12 ) );
            invGain_Q30 = LPC_inverse_pred_gain_QA_neon( Atmp_QA, order );
        }
    }

#ifdef OPUS_CHECK_ASM
    silk_assert( invGain_Q30_c == invGain_Q30 );
#endif

    return invGain_Q30;
}