Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / arch / mips / math-emu / dp_sqrt.c

diff --git a/kernel/arch/mips/math-emu/dp_sqrt.c b/kernel/arch/mips/math-emu/dp_sqrt.c
new file mode 100644 (file)
index 0000000..cd5bc08
--- /dev/null
+++ b/kernel/arch/mips/math-emu/dp_sqrt.c
@@ -0,0 +1,163 @@
+/* IEEE754 floating point arithmetic
+ * double precision square root
+ */
+/*
+ * MIPS floating point support
+ * Copyright (C) 1994-2000 Algorithmics Ltd.
+ *
+ *  This program is free software; you can distribute it and/or modify it
+ *  under the terms of the GNU General Public License (Version 2) as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+ */
+
+#include "ieee754dp.h"
+
+static const unsigned table[] = {
+       0, 1204, 3062, 5746, 9193, 13348, 18162, 23592,
+       29598, 36145, 43202, 50740, 58733, 67158, 75992,
+       85215, 83599, 71378, 60428, 50647, 41945, 34246,
+       27478, 21581, 16499, 12183, 8588, 5674, 3403,
+       1742, 661, 130
+};
+
+union ieee754dp ieee754dp_sqrt(union ieee754dp x)
+{
+       struct _ieee754_csr oldcsr;
+       union ieee754dp y, z, t;
+       unsigned scalx, yh;
+       COMPXDP;
+
+       EXPLODEXDP;
+       ieee754_clearcx();
+       FLUSHXDP;
+
+       /* x == INF or NAN? */
+       switch (xc) {
+       case IEEE754_CLASS_SNAN:
+               return ieee754dp_nanxcpt(x);
+
+       case IEEE754_CLASS_QNAN:
+               /* sqrt(Nan) = Nan */
+               return x;
+
+       case IEEE754_CLASS_ZERO:
+               /* sqrt(0) = 0 */
+               return x;
+
+       case IEEE754_CLASS_INF:
+               if (xs) {
+                       /* sqrt(-Inf) = Nan */
+                       ieee754_setcx(IEEE754_INVALID_OPERATION);
+                       return ieee754dp_indef();
+               }
+               /* sqrt(+Inf) = Inf */
+               return x;
+
+       case IEEE754_CLASS_DNORM:
+               DPDNORMX;
+               /* fall through */
+
+       case IEEE754_CLASS_NORM:
+               if (xs) {
+                       /* sqrt(-x) = Nan */
+                       ieee754_setcx(IEEE754_INVALID_OPERATION);
+                       return ieee754dp_indef();
+               }
+               break;
+       }
+
+       /* save old csr; switch off INX enable & flag; set RN rounding */
+       oldcsr = ieee754_csr;
+       ieee754_csr.mx &= ~IEEE754_INEXACT;
+       ieee754_csr.sx &= ~IEEE754_INEXACT;
+       ieee754_csr.rm = FPU_CSR_RN;
+
+       /* adjust exponent to prevent overflow */
+       scalx = 0;
+       if (xe > 512) {         /* x > 2**-512? */
+               xe -= 512;      /* x = x / 2**512 */
+               scalx += 256;
+       } else if (xe < -512) { /* x < 2**-512? */
+               xe += 512;      /* x = x * 2**512 */
+               scalx -= 256;
+       }
+
+       y = x = builddp(0, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT);
+
+       /* magic initial approximation to almost 8 sig. bits */
+       yh = y.bits >> 32;
+       yh = (yh >> 1) + 0x1ff80000;
+       yh = yh - table[(yh >> 15) & 31];
+       y.bits = ((u64) yh << 32) | (y.bits & 0xffffffff);
+
+       /* Heron's rule once with correction to improve to ~18 sig. bits */
+       /* t=x/y; y=y+t; py[n0]=py[n0]-0x00100006; py[n1]=0; */
+       t = ieee754dp_div(x, y);
+       y = ieee754dp_add(y, t);
+       y.bits -= 0x0010000600000000LL;
+       y.bits &= 0xffffffff00000000LL;
+
+       /* triple to almost 56 sig. bits: y ~= sqrt(x) to within 1 ulp */
+       /* t=y*y; z=t;  pt[n0]+=0x00100000; t+=z; z=(x-z)*y; */
+       z = t = ieee754dp_mul(y, y);
+       t.bexp += 0x001;
+       t = ieee754dp_add(t, z);
+       z = ieee754dp_mul(ieee754dp_sub(x, z), y);
+
+       /* t=z/(t+x) ;  pt[n0]+=0x00100000; y+=t; */
+       t = ieee754dp_div(z, ieee754dp_add(t, x));
+       t.bexp += 0x001;
+       y = ieee754dp_add(y, t);
+
+       /* twiddle last bit to force y correctly rounded */
+
+       /* set RZ, clear INEX flag */
+       ieee754_csr.rm = FPU_CSR_RZ;
+       ieee754_csr.sx &= ~IEEE754_INEXACT;
+
+       /* t=x/y; ...chopped quotient, possibly inexact */
+       t = ieee754dp_div(x, y);
+
+       if (ieee754_csr.sx & IEEE754_INEXACT || t.bits != y.bits) {
+
+               if (!(ieee754_csr.sx & IEEE754_INEXACT))
+                       /* t = t-ulp */
+                       t.bits -= 1;
+
+               /* add inexact to result status */
+               oldcsr.cx |= IEEE754_INEXACT;
+               oldcsr.sx |= IEEE754_INEXACT;
+
+               switch (oldcsr.rm) {
+               case FPU_CSR_RU:
+                       y.bits += 1;
+                       /* drop through */
+               case FPU_CSR_RN:
+                       t.bits += 1;
+                       break;
+               }
+
+               /* y=y+t; ...chopped sum */
+               y = ieee754dp_add(y, t);
+
+               /* adjust scalx for correctly rounded sqrt(x) */
+               scalx -= 1;
+       }
+
+       /* py[n0]=py[n0]+scalx; ...scale back y */
+       y.bexp += scalx;
+
+       /* restore rounding mode, possibly set inexact */
+       ieee754_csr = oldcsr;
+
+       return y;
+}