f16_sqrt.c File Reference

#include <stdbool.h>
#include <stdint.h>
#include "platform.h"
#include "internals.h"
#include "specialize.h"
#include "softfloat.h"

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Functions
float16_t	f16_sqrt (float16_t a)

Variables
const uint16_t	softfloat_approxRecipSqrt_1k0s []
const uint16_t	softfloat_approxRecipSqrt_1k1s []

Function Documentation

f16_sqrt()

float16_t f16_sqrt

(

float16_t

a

)

Definition at line 47 of file f16_sqrt.c.

{
    union ui16_f16 uA;
    uint_fast16_t uiA;
    bool signA;
    int_fast8_t expA;
    uint_fast16_t sigA, uiZ;
    struct exp8_sig16 normExpSig;
    int_fast8_t expZ;
    int index;
    uint_fast16_t r0;
    uint_fast32_t ESqrR0;
    uint16_t sigma0;
    uint_fast16_t recipSqrt16, sigZ, shiftedSigZ;
    uint16_t negRem;
    union ui16_f16 uZ;
 
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    uA.f = a;
    uiA = uA.ui;
    signA = signF16UI( uiA );
    expA  = expF16UI( uiA );
    sigA  = fracF16UI( uiA );
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    if ( expA == 0x1F ) {
        if ( sigA ) {
            uiZ = softfloat_propagateNaNF16UI( uiA, 0 );
            goto uiZ;
        }
        if ( ! signA ) return a;
        goto invalid;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    if ( signA ) {
        if ( ! (expA | sigA) ) return a;
        goto invalid;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    if ( ! expA ) {
        if ( ! sigA ) return a;
        normExpSig = softfloat_normSubnormalF16Sig( sigA );
        expA = normExpSig.exp;
        sigA = normExpSig.sig;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    expZ = ((expA - 0xF)>>1) + 0xE;
    expA &= 1;
    sigA |= 0x0400;
    index = (sigA>>6 & 0xE) + expA;
    r0 = softfloat_approxRecipSqrt_1k0s[index]
             - (((uint_fast32_t) softfloat_approxRecipSqrt_1k1s[index]
                     * (sigA & 0x7F))
                    >>11);
    ESqrR0 = ((uint_fast32_t) r0 * r0)>>1;
    if ( expA ) ESqrR0 >>= 1;
    sigma0 = ~(uint_fast16_t) ((ESqrR0 * sigA)>>16);
    recipSqrt16 = r0 + (((uint_fast32_t) r0 * sigma0)>>25);
    if ( ! (recipSqrt16 & 0x8000) ) recipSqrt16 = 0x8000;
    sigZ = ((uint_fast32_t) (sigA<<5) * recipSqrt16)>>16;
    if ( expA ) sigZ >>= 1;
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    ++sigZ;
    if ( ! (sigZ & 7) ) {
        shiftedSigZ = sigZ>>1;
        negRem = shiftedSigZ * shiftedSigZ;
        sigZ &= ~1;
        if ( negRem & 0x8000 ) {
            sigZ |= 1;
        } else {
            if ( negRem ) --sigZ;
        }
    }
    return softfloat_roundPackToF16( 0, expZ, sigZ );
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
 invalid:
    softfloat_raiseFlags( softfloat_flag_invalid );
    uiZ = defaultNaNF16UI;
 uiZ:
    uZ.ui = uiZ;
    return uZ.f;
 
}

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Variable Documentation

softfloat_approxRecipSqrt_1k0s

const uint16_t softfloat_approxRecipSqrt_1k0s[]

extern

Definition at line 41 of file s_approxRecipSqrt_1Ks.c.

                                                    {
    0xB4C9, 0xFFAB, 0xAA7D, 0xF11C, 0xA1C5, 0xE4C7, 0x9A43, 0xDA29,
    0x93B5, 0xD0E5, 0x8DED, 0xC8B7, 0x88C6, 0xC16D, 0x8424, 0xBAE1
};

softfloat_approxRecipSqrt_1k1s

const uint16_t softfloat_approxRecipSqrt_1k1s[]

extern

Definition at line 45 of file s_approxRecipSqrt_1Ks.c.

                                                    {
    0xA5A5, 0xEA42, 0x8C21, 0xC62D, 0x788F, 0xAA7F, 0x6928, 0x94B6,
    0x5CC7, 0x8335, 0x52A6, 0x74E2, 0x4A3E, 0x68FE, 0x432B, 0x5EFD
};