f16_rem.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_rem (float16_t a, float16_t b)

Function Documentation

f16_rem()

float16_t f16_rem	(	float16_t	a,
		float16_t	b )

Definition at line 44 of file f16_rem.c.

{
    union ui16_f16 uA;
    uint_fast16_t uiA;
    bool signA;
    int_fast8_t expA;
    uint_fast16_t sigA;
    union ui16_f16 uB;
    uint_fast16_t uiB;
    int_fast8_t expB;
    uint_fast16_t sigB;
    struct exp8_sig16 normExpSig;
    uint16_t rem;
    int_fast8_t expDiff;
    uint_fast16_t q;
    uint32_t recip32, q32;
    uint16_t altRem, meanRem;
    bool signRem;
    uint_fast16_t uiZ;
    union ui16_f16 uZ;
 
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    uA.f = a;
    uiA = uA.ui;
    signA = signF16UI( uiA );
    expA  = expF16UI( uiA );
    sigA  = fracF16UI( uiA );
    uB.f = b;
    uiB = uB.ui;
    expB = expF16UI( uiB );
    sigB = fracF16UI( uiB );
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    if ( expA == 0x1F ) {
        if ( sigA || ((expB == 0x1F) && sigB) ) goto propagateNaN;
        goto invalid;
    }
    if ( expB == 0x1F ) {
        if ( sigB ) goto propagateNaN;
        return a;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    if ( ! expB ) {
        if ( ! sigB ) goto invalid;
        normExpSig = softfloat_normSubnormalF16Sig( sigB );
        expB = normExpSig.exp;
        sigB = normExpSig.sig;
    }
    if ( ! expA ) {
        if ( ! sigA ) return a;
        normExpSig = softfloat_normSubnormalF16Sig( sigA );
        expA = normExpSig.exp;
        sigA = normExpSig.sig;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    rem = sigA | 0x0400;
    sigB |= 0x0400;
    expDiff = expA - expB;
    if ( expDiff < 1 ) {
        if ( expDiff < -1 ) return a;
        sigB <<= 3;
        if ( expDiff ) {
            rem <<= 2;
            q = 0;
        } else {
            rem <<= 3;
            q = (sigB <= rem);
            if ( q ) rem -= sigB;
        }
    } else {
        recip32 = softfloat_approxRecip32_1( (uint_fast32_t) sigB<<21 );
        /*--------------------------------------------------------------------
        | Changing the shift of `rem' here requires also changing the initial
        | subtraction from `expDiff'.
        *--------------------------------------------------------------------*/
        rem <<= 4;
        expDiff -= 31;
        /*--------------------------------------------------------------------
        | The scale of `sigB' affects how many bits are obtained during each
        | cycle of the loop.  Currently this is 29 bits per loop iteration,
        | which is believed to be the maximum possible.
        *--------------------------------------------------------------------*/
        sigB <<= 3;
        for (;;) {
            q32 = (rem * (uint_fast64_t) recip32)>>16;
            if ( expDiff < 0 ) break;
            rem = -((uint_fast16_t) q32 * sigB);
            expDiff -= 29;
        }
        /*--------------------------------------------------------------------
        | (`expDiff' cannot be less than -30 here.)
        *--------------------------------------------------------------------*/
        q32 >>= ~expDiff & 31;
        q = q32;
        rem = (rem<<(expDiff + 30)) - q * sigB;
    }
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
    do {
        altRem = rem;
        ++q;
        rem -= sigB;
    } while ( ! (rem & 0x8000) );
    meanRem = rem + altRem;
    if ( (meanRem & 0x8000) || (! meanRem && (q & 1)) ) rem = altRem;
    signRem = signA;
    if ( 0x8000 <= rem ) {
        signRem = ! signRem;
        rem = -rem;
    }
    return softfloat_normRoundPackToF16( signRem, expB, rem );
    /*------------------------------------------------------------------------
    *------------------------------------------------------------------------*/
 propagateNaN:
    uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
    goto uiZ;
 invalid:
    softfloat_raiseFlags( softfloat_flag_invalid );
    uiZ = defaultNaNF16UI;
 uiZ:
    uZ.ui = uiZ;
    return uZ.f;
 
}

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