GK SDK 源码库: XMIPCLinuxV100R005C00SPC030 (kernel/tools/open_source excluded)

source/bootloader/u-boot-2020.01/post/lib_powerpc/fpu/darwin-ldouble.c

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+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Borrowed from GCC 4.2.2 (which still was GPL v2+)
+ */
+/* 128-bit long double support routines for Darwin.
+   Copyright (C) 1993, 2003, 2004, 2005, 2006, 2007
+   Free Software Foundation, Inc.
+
+This file is part of GCC.
+ */
+
+/*
+ * Implementations of floating-point long double basic arithmetic
+ * functions called by the IBM C compiler when generating code for
+ * PowerPC platforms.  In particular, the following functions are
+ * implemented: __gcc_qadd, __gcc_qsub, __gcc_qmul, and __gcc_qdiv.
+ * Double-double algorithms are based on the paper "Doubled-Precision
+ * IEEE Standard 754 Floating-Point Arithmetic" by W. Kahan, February 26,
+ * 1987.  An alternative published reference is "Software for
+ * Doubled-Precision Floating-Point Computations", by Seppo Linnainmaa,
+ * ACM TOMS vol 7 no 3, September 1981, pages 272-283.
+ */
+
+/*
+ * Each long double is made up of two IEEE doubles.  The value of the
+ * long double is the sum of the values of the two parts.  The most
+ * significant part is required to be the value of the long double
+ * rounded to the nearest double, as specified by IEEE.  For Inf
+ * values, the least significant part is required to be one of +0.0 or
+ * -0.0.  No other requirements are made; so, for example, 1.0 may be
+ * represented as (1.0, +0.0) or (1.0, -0.0), and the low part of a
+ * NaN is don't-care.
+ *
+ * This code currently assumes big-endian.
+ */
+
+#define fabs(x) __builtin_fabs(x)
+#define isless(x, y) __builtin_isless(x, y)
+#define inf() __builtin_inf()
+#define unlikely(x) __builtin_expect((x), 0)
+#define nonfinite(a) unlikely(!isless(fabs(a), inf()))
+
+typedef union {
+	long double ldval;
+	double dval[2];
+} longDblUnion;
+
+/* Add two 'long double' values and return the result.	*/
+long double __gcc_qadd(double a, double aa, double c, double cc)
+{
+	longDblUnion x;
+	double z, q, zz, xh;
+
+	z = a + c;
+
+	if (nonfinite(z)) {
+		z = cc + aa + c + a;
+		if (nonfinite(z))
+			return z;
+		x.dval[0] = z;	/* Will always be DBL_MAX.  */
+		zz = aa + cc;
+		if (fabs(a) > fabs(c))
+			x.dval[1] = a - z + c + zz;
+		else
+			x.dval[1] = c - z + a + zz;
+	} else {
+		q = a - z;
+		zz = q + c + (a - (q + z)) + aa + cc;
+
+		/* Keep -0 result.  */
+		if (zz == 0.0)
+			return z;
+
+		xh = z + zz;
+		if (nonfinite(xh))
+			return xh;
+
+		x.dval[0] = xh;
+		x.dval[1] = z - xh + zz;
+	}
+	return x.ldval;
+}
+
+long double __gcc_qsub(double a, double b, double c, double d)
+{
+	return __gcc_qadd(a, b, -c, -d);
+}
+
+long double __gcc_qmul(double a, double b, double c, double d)
+{
+	longDblUnion z;
+	double t, tau, u, v, w;
+
+	t = a * c;		/* Highest order double term.  */
+
+	if (unlikely(t == 0)	/* Preserve -0.  */
+	    || nonfinite(t))
+		return t;
+
+	/* Sum terms of two highest orders. */
+
+	/* Use fused multiply-add to get low part of a * c.  */
+#ifndef __NO_FPRS__
+	asm("fmsub %0,%1,%2,%3" : "=f"(tau) : "f"(a), "f"(c), "f"(t));
+#else
+	tau = fmsub(a, c, t);
+#endif
+	v = a * d;
+	w = b * c;
+	tau += v + w;		/* Add in other second-order terms.  */
+	u = t + tau;
+
+	/* Construct long double result.  */
+	if (nonfinite(u))
+		return u;
+	z.dval[0] = u;
+	z.dval[1] = (t - u) + tau;
+	return z.ldval;
+}