/* Implementations for copysign, ilogb, and nextafter for float16 based on
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* corresponding float32 implementations in
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* bionic/libm/upstream-freebsd/lib/msun/src
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include "rs_core.rsh"
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#include "rs_f16_util.h"
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// Based on bionic/libm/upstream-freebsd/lib/msun/src/s_copysignf.c
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extern half __attribute__((overloadable)) copysign(half x, half y) {
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short hx, hy;
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GET_HALF_WORD(hx, x);
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GET_HALF_WORD(hy, y);
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SET_HALF_WORD(x, (hx & 0x7fff) | (hy & 0x8000));
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return x;
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}
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// Based on bionic/libm/upstream-freebsd/lib/msun/src/s_frexpf.c
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extern half __attribute__((overloadable)) frexp(half x, int *eptr) {
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short hx, ix;
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static const half two12 = 4096;
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GET_HALF_WORD(hx, x);
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ix = hx & 0x7fff;
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*eptr = 0;
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if (ix >= 0x7c00 || ix == 0) return x; // NaN, infinity or zero
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if (ix <= 0x0400) {
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// x is subnormal. Scale it by 2^12 (and adjust eptr accordingly) so
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// that even the smallest subnormal value becomes normal.
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x *= two12;
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GET_HALF_WORD(hx, x);
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ix = hx & 0x7fff;
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*eptr = -12;
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}
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// Adjust eptr by (non-biased exponent of hx + 1). Set the non-biased
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// exponent to be equal to -1 so that abs(hx) is between 0.5 and 1.
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*eptr += (ix >> 10) - 14;
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hx = (hx & 0x83ff) | 0x3800;
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SET_HALF_WORD(x, hx);
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return x;
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}
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// Based on bionic/libm/upstream-freebsd/lib/msun/src/s_ilogbf.c
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extern int __attribute__((overloadable)) ilogb(half x) {
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const int RS_INT_MAX = 0x7fffffff;
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const int RS_INT_MIN = 0x80000000;
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short hx, ix;
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GET_HALF_WORD(hx, x);
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hx &= 0x7fff;
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if (hx < 0x0400) { // subnormal
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if (hx == 0)
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return RS_INT_MIN; // for zero
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for (hx <<= 5, ix = -14; hx > 0; hx <<= 1)
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ix -= 1;
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return ix;
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}
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else if (hx < 0x7c00) {
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return (hx >> 10) - 15;
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}
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else { // hx >= 0x7c00
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return RS_INT_MAX; // for NaN and infinity
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}
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}
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// Based on bionic/libm/upstream-freebsd/lib/msun/src/s_modff.c
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extern half __attribute__((overloadable)) modf(half x, half *iptr) {
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short i0, j0;
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unsigned short i;
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GET_HALF_WORD(i0, x);
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j0 = ((i0 >> 10) & 0x1f) - 15; // exponent of x
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if (j0 < 10) {
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if (j0 < 0) { // No integral part
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SET_HALF_WORD(*iptr, i0 & 0x8000); // *iptr = +/- 0
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return x;
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}
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else {
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i = 0x03ff >> j0; // mask to check fractional parts of x
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if ((i0 & i) == 0) { // no bits set in fractional part
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*iptr = x;
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SET_HALF_WORD(x, i0 & 0x8000);
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return x;
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}
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else {
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SET_HALF_WORD(*iptr, i0 & ~i); // zero out fractional parts
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return x - *iptr;
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}
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}
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}
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else { // No fractional part
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unsigned short ix;
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*iptr = x;
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if (x != x)
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return x;
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GET_HALF_WORD(ix, x);
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SET_HALF_WORD(x, ix & 0x8000); // x = +/- 0
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return x;
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}
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}
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// Based on bionic/libm/upstream-freebsd/lib/msun/src/s_nextafterf.c
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extern half __attribute__((overloadable)) nextafter(half x, half y) {
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short hx, hy, ix, iy;
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GET_HALF_WORD(hx, x);
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GET_HALF_WORD(hy, y);
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ix = hx & 0x7fff; // |x|
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iy = hy & 0x7fff; // |y|
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if ((ix > 0x7c00) || // x is nan
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(iy > 0x7c00)) // y is nan
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return x + y; // return nan
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if (x == y) return y; // x == y. return y
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if (ix == 0) {
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SET_HALF_WORD(x, (hy & 0x8000) | 1);
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return x;
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}
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if (hx >= 0) { // x >= 0
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if (hx > hy)
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hx -= 1; // x > y, x -= 1 ulp
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else
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hx += 1; // x < y, x += 1 ulp
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}
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else { // x < 0
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if (hy>= 0 || hx > hy)
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hx -= 1; // x < y, x -= 1 ulp
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else
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hx += 1;
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}
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SET_HALF_WORD(x, hx);
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return x;
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}
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