LXR uboot/post/lib_powerpc/fpu/darwin-ldouble.c

   1/*
   2 * Borrowed from GCC 4.2.2 (which still was GPL v2+)
   3 */
   4/* 128-bit long double support routines for Darwin.
   5   Copyright (C) 1993, 2003, 2004, 2005, 2006, 2007
   6   Free Software Foundation, Inc.
   7
   8This file is part of GCC.
   9
  10 * SPDX-License-Identifier:     GPL-2.0+
  11 */
  12
  13/*
  14 * Implementations of floating-point long double basic arithmetic
  15 * functions called by the IBM C compiler when generating code for
  16 * PowerPC platforms.  In particular, the following functions are
  17 * implemented: __gcc_qadd, __gcc_qsub, __gcc_qmul, and __gcc_qdiv.
  18 * Double-double algorithms are based on the paper "Doubled-Precision
  19 * IEEE Standard 754 Floating-Point Arithmetic" by W. Kahan, February 26,
  20 * 1987.  An alternative published reference is "Software for
  21 * Doubled-Precision Floating-Point Computations", by Seppo Linnainmaa,
  22 * ACM TOMS vol 7 no 3, September 1981, pages 272-283.
  23 */
  24
  25/*
  26 * Each long double is made up of two IEEE doubles.  The value of the
  27 * long double is the sum of the values of the two parts.  The most
  28 * significant part is required to be the value of the long double
  29 * rounded to the nearest double, as specified by IEEE.  For Inf
  30 * values, the least significant part is required to be one of +0.0 or
  31 * -0.0.  No other requirements are made; so, for example, 1.0 may be
  32 * represented as (1.0, +0.0) or (1.0, -0.0), and the low part of a
  33 * NaN is don't-care.
  34 *
  35 * This code currently assumes big-endian.
  36 */
  37
  38#define fabs(x) __builtin_fabs(x)
  39#define isless(x, y) __builtin_isless(x, y)
  40#define inf() __builtin_inf()
  41#define unlikely(x) __builtin_expect((x), 0)
  42#define nonfinite(a) unlikely(!isless(fabs(a), inf()))
  43
  44typedef union {
  45        long double ldval;
  46        double dval[2];
  47} longDblUnion;
  48
  49/* Add two 'long double' values and return the result.  */
  50long double __gcc_qadd(double a, double aa, double c, double cc)
  51{
  52        longDblUnion x;
  53        double z, q, zz, xh;
  54
  55        z = a + c;
  56
  57        if (nonfinite(z)) {
  58                z = cc + aa + c + a;
  59                if (nonfinite(z))
  60                        return z;
  61                x.dval[0] = z;  /* Will always be DBL_MAX.  */
  62                zz = aa + cc;
  63                if (fabs(a) > fabs(c))
  64                        x.dval[1] = a - z + c + zz;
  65                else
  66                        x.dval[1] = c - z + a + zz;
  67        } else {
  68                q = a - z;
  69                zz = q + c + (a - (q + z)) + aa + cc;
  70
  71                /* Keep -0 result.  */
  72                if (zz == 0.0)
  73                        return z;
  74
  75                xh = z + zz;
  76                if (nonfinite(xh))
  77                        return xh;
  78
  79                x.dval[0] = xh;
  80                x.dval[1] = z - xh + zz;
  81        }
  82        return x.ldval;
  83}
  84
  85long double __gcc_qsub(double a, double b, double c, double d)
  86{
  87        return __gcc_qadd(a, b, -c, -d);
  88}
  89
  90long double __gcc_qmul(double a, double b, double c, double d)
  91{
  92        longDblUnion z;
  93        double t, tau, u, v, w;
  94
  95        t = a * c;              /* Highest order double term.  */
  96
  97        if (unlikely(t == 0)    /* Preserve -0.  */
  98            || nonfinite(t))
  99                return t;
 100
 101        /* Sum terms of two highest orders. */
 102
 103        /* Use fused multiply-add to get low part of a * c.  */
 104#ifndef __NO_FPRS__
 105        asm("fmsub %0,%1,%2,%3" : "=f"(tau) : "f"(a), "f"(c), "f"(t));
 106#else
 107        tau = fmsub(a, c, t);
 108#endif
 109        v = a * d;
 110        w = b * c;
 111        tau += v + w;           /* Add in other second-order terms.  */
 112        u = t + tau;
 113
 114        /* Construct long double result.  */
 115        if (nonfinite(u))
 116                return u;
 117        z.dval[0] = u;
 118        z.dval[1] = (t - u) + tau;
 119        return z.ldval;
 120}
 121