libclc/generic/lib/math/clc_hypot.cl

/*
 * Copyright (c) 2014 Advanced Micro Devices, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include <clc/clc.h>
#include <math/clc_hypot.h>

#include "config.h"
#include "math.h"
#include "../clcmacro.h"

// Returns sqrt(x*x + y*y) with no overflow or underflow unless the result warrants it
_CLC_DEF _CLC_OVERLOAD float __clc_hypot(float x, float y)
{
    uint ux = as_uint(x);
    uint aux = ux & EXSIGNBIT_SP32;
    uint uy = as_uint(y);
    uint auy = uy & EXSIGNBIT_SP32;
    float retval;
    int c = aux > auy;
    ux = c ? aux : auy;
    uy = c ? auy : aux;

    int xexp = clamp((int)(ux >> EXPSHIFTBITS_SP32) - EXPBIAS_SP32, -126, 126);
    float fx_exp = as_float((xexp + EXPBIAS_SP32) << EXPSHIFTBITS_SP32);
    float fi_exp = as_float((-xexp + EXPBIAS_SP32) << EXPSHIFTBITS_SP32);
    float fx = as_float(ux) * fi_exp;
    float fy = as_float(uy) * fi_exp;
    retval = sqrt(mad(fx, fx, fy*fy)) * fx_exp;

    retval = ux > PINFBITPATT_SP32 | uy == 0 ? as_float(ux) : retval;
    retval = ux == PINFBITPATT_SP32 | uy == PINFBITPATT_SP32 ? as_float(PINFBITPATT_SP32) : retval;
    return retval;
}
_CLC_BINARY_VECTORIZE(_CLC_DEF _CLC_OVERLOAD, float, __clc_hypot, float, float)

#ifdef cl_khr_fp64
_CLC_DEF _CLC_OVERLOAD double __clc_hypot(double x, double y)
{
    ulong ux = as_ulong(x) & ~SIGNBIT_DP64;
    int xexp = ux >> EXPSHIFTBITS_DP64;
    x = as_double(ux);

    ulong uy = as_ulong(y) & ~SIGNBIT_DP64;
    int yexp = uy >> EXPSHIFTBITS_DP64;
    y = as_double(uy);

    int c = xexp > EXPBIAS_DP64 + 500 | yexp > EXPBIAS_DP64 + 500;
    double preadjust = c ? 0x1.0p-600 : 1.0;
    double postadjust = c ? 0x1.0p+600 : 1.0;

    c = xexp < EXPBIAS_DP64 - 500 | yexp < EXPBIAS_DP64 - 500;
    preadjust = c ? 0x1.0p+600 : preadjust;
    postadjust = c ? 0x1.0p-600 : postadjust;

    double ax = x * preadjust;
    double ay = y * preadjust;

    // The post adjust may overflow, but this can't be avoided in any case
    double r = sqrt(fma(ax, ax, ay*ay)) * postadjust;

    // If the difference in exponents between x and y is large
    double s = x + y;
    c = abs(xexp - yexp) > MANTLENGTH_DP64 + 1;
    r = c ? s : r;

    // Check for NaN
    //c = x != x | y != y;
    c = isnan(x) | isnan(y);
    r = c ? as_double(QNANBITPATT_DP64) : r;

    // If either is Inf, we must return Inf
    c = x == as_double(PINFBITPATT_DP64) | y == as_double(PINFBITPATT_DP64);
    r = c ? as_double(PINFBITPATT_DP64) : r;

    return r;
}

_CLC_BINARY_VECTORIZE(_CLC_DEF _CLC_OVERLOAD, double, __clc_hypot, double, double)
#endif