From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 arch/x86/math-emu/poly_2xm1.c | 145 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 arch/x86/math-emu/poly_2xm1.c

(limited to 'arch/x86/math-emu/poly_2xm1.c')

diff --git a/arch/x86/math-emu/poly_2xm1.c b/arch/x86/math-emu/poly_2xm1.c
new file mode 100644
index 000000000..b00e9e10c
--- /dev/null
+++ b/arch/x86/math-emu/poly_2xm1.c
@@ -0,0 +1,145 @@
+/*---------------------------------------------------------------------------+
+ |  poly_2xm1.c                                                              |
+ |                                                                           |
+ | Function to compute 2^x-1 by a polynomial approximation.                  |
+ |                                                                           |
+ | Copyright (C) 1992,1993,1994,1997                                         |
+ |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ |                  E-mail   billm@suburbia.net                              |
+ |                                                                           |
+ |                                                                           |
+ +---------------------------------------------------------------------------*/
+
+#include "exception.h"
+#include "reg_constant.h"
+#include "fpu_emu.h"
+#include "fpu_system.h"
+#include "control_w.h"
+#include "poly.h"
+
+#define	HIPOWER	11
+static const unsigned long long lterms[HIPOWER] = {
+	0x0000000000000000LL,	/* This term done separately as 12 bytes */
+	0xf5fdeffc162c7543LL,
+	0x1c6b08d704a0bfa6LL,
+	0x0276556df749cc21LL,
+	0x002bb0ffcf14f6b8LL,
+	0x0002861225ef751cLL,
+	0x00001ffcbfcd5422LL,
+	0x00000162c005d5f1LL,
+	0x0000000da96ccb1bLL,
+	0x0000000078d1b897LL,
+	0x000000000422b029LL
+};
+
+static const Xsig hiterm = MK_XSIG(0xb17217f7, 0xd1cf79ab, 0xc8a39194);
+
+/* Four slices: 0.0 : 0.25 : 0.50 : 0.75 : 1.0,
+   These numbers are 2^(1/4), 2^(1/2), and 2^(3/4)
+ */
+static const Xsig shiftterm0 = MK_XSIG(0, 0, 0);
+static const Xsig shiftterm1 = MK_XSIG(0x9837f051, 0x8db8a96f, 0x46ad2318);
+static const Xsig shiftterm2 = MK_XSIG(0xb504f333, 0xf9de6484, 0x597d89b3);
+static const Xsig shiftterm3 = MK_XSIG(0xd744fcca, 0xd69d6af4, 0x39a68bb9);
+
+static const Xsig *shiftterm[] = { &shiftterm0, &shiftterm1,
+	&shiftterm2, &shiftterm3
+};
+
+/*--- poly_2xm1() -----------------------------------------------------------+
+ | Requires st(0) which is TAG_Valid and < 1.                                |
+ +---------------------------------------------------------------------------*/
+int poly_2xm1(u_char sign, FPU_REG *arg, FPU_REG *result)
+{
+	long int exponent, shift;
+	unsigned long long Xll;
+	Xsig accumulator, Denom, argSignif;
+	u_char tag;
+
+	exponent = exponent16(arg);
+
+#ifdef PARANOID
+	if (exponent >= 0) {	/* Don't want a |number| >= 1.0 */
+		/* Number negative, too large, or not Valid. */
+		EXCEPTION(EX_INTERNAL | 0x127);
+		return 1;
+	}
+#endif /* PARANOID */
+
+	argSignif.lsw = 0;
+	XSIG_LL(argSignif) = Xll = significand(arg);
+
+	if (exponent == -1) {
+		shift = (argSignif.msw & 0x40000000) ? 3 : 2;
+		/* subtract 0.5 or 0.75 */
+		exponent -= 2;
+		XSIG_LL(argSignif) <<= 2;
+		Xll <<= 2;
+	} else if (exponent == -2) {
+		shift = 1;
+		/* subtract 0.25 */
+		exponent--;
+		XSIG_LL(argSignif) <<= 1;
+		Xll <<= 1;
+	} else
+		shift = 0;
+
+	if (exponent < -2) {
+		/* Shift the argument right by the required places. */
+		if (FPU_shrx(&Xll, -2 - exponent) >= 0x80000000U)
+			Xll++;	/* round up */
+	}
+
+	accumulator.lsw = accumulator.midw = accumulator.msw = 0;
+	polynomial_Xsig(&accumulator, &Xll, lterms, HIPOWER - 1);
+	mul_Xsig_Xsig(&accumulator, &argSignif);
+	shr_Xsig(&accumulator, 3);
+
+	mul_Xsig_Xsig(&argSignif, &hiterm);	/* The leading term */
+	add_two_Xsig(&accumulator, &argSignif, &exponent);
+
+	if (shift) {
+		/* The argument is large, use the identity:
+		   f(x+a) = f(a) * (f(x) + 1) - 1;
+		 */
+		shr_Xsig(&accumulator, -exponent);
+		accumulator.msw |= 0x80000000;	/* add 1.0 */
+		mul_Xsig_Xsig(&accumulator, shiftterm[shift]);
+		accumulator.msw &= 0x3fffffff;	/* subtract 1.0 */
+		exponent = 1;
+	}
+
+	if (sign != SIGN_POS) {
+		/* The argument is negative, use the identity:
+		   f(-x) = -f(x) / (1 + f(x))
+		 */
+		Denom.lsw = accumulator.lsw;
+		XSIG_LL(Denom) = XSIG_LL(accumulator);
+		if (exponent < 0)
+			shr_Xsig(&Denom, -exponent);
+		else if (exponent > 0) {
+			/* exponent must be 1 here */
+			XSIG_LL(Denom) <<= 1;
+			if (Denom.lsw & 0x80000000)
+				XSIG_LL(Denom) |= 1;
+			(Denom.lsw) <<= 1;
+		}
+		Denom.msw |= 0x80000000;	/* add 1.0 */
+		div_Xsig(&accumulator, &Denom, &accumulator);
+	}
+
+	/* Convert to 64 bit signed-compatible */
+	exponent += round_Xsig(&accumulator);
+
+	result = &st(0);
+	significand(result) = XSIG_LL(accumulator);
+	setexponent16(result, exponent);
+
+	tag = FPU_round(result, 1, 0, FULL_PRECISION, sign);
+
+	setsign(result, sign);
+	FPU_settag0(tag);
+
+	return 0;
+
+}
-- 
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