Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 298 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/ieee754/ldbl-128/s_fmal.c b/REORG.TODO/sysdeps/ieee754/ldbl-128/s_fmal.c
new file mode 100644
index 0000000000..40c4e73d2b
--- /dev/null
+++ b/REORG.TODO/sysdeps/ieee754/ldbl-128/s_fmal.c
@@ -0,0 +1,298 @@
+/* Compute x * y + z as ternary operation.
+   Copyright (C) 2010-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Jakub Jelinek <jakub@redhat.com>, 2010.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <float.h>
+#include <math.h>
+#include <fenv.h>
+#include <ieee754.h>
+#include <math_private.h>
+#include <tininess.h>
+
+/* This implementation uses rounding to odd to avoid problems with
+   double rounding.  See a paper by Boldo and Melquiond:
+   http://www.lri.fr/~melquion/doc/08-tc.pdf  */
+
+_Float128
+__fmal (_Float128 x, _Float128 y, _Float128 z)
+{
+  union ieee854_long_double u, v, w;
+  int adjust = 0;
+  u.d = x;
+  v.d = y;
+  w.d = z;
+  if (__builtin_expect (u.ieee.exponent + v.ieee.exponent
+			>= 0x7fff + IEEE854_LONG_DOUBLE_BIAS
+			   - LDBL_MANT_DIG, 0)
+      || __builtin_expect (u.ieee.exponent >= 0x7fff - LDBL_MANT_DIG, 0)
+      || __builtin_expect (v.ieee.exponent >= 0x7fff - LDBL_MANT_DIG, 0)
+      || __builtin_expect (w.ieee.exponent >= 0x7fff - LDBL_MANT_DIG, 0)
+      || __builtin_expect (u.ieee.exponent + v.ieee.exponent
+			   <= IEEE854_LONG_DOUBLE_BIAS + LDBL_MANT_DIG, 0))
+    {
+      /* If z is Inf, but x and y are finite, the result should be
+	 z rather than NaN.  */
+      if (w.ieee.exponent == 0x7fff
+	  && u.ieee.exponent != 0x7fff
+          && v.ieee.exponent != 0x7fff)
+	return (z + x) + y;
+      /* If z is zero and x are y are nonzero, compute the result
+	 as x * y to avoid the wrong sign of a zero result if x * y
+	 underflows to 0.  */
+      if (z == 0 && x != 0 && y != 0)
+	return x * y;
+      /* If x or y or z is Inf/NaN, or if x * y is zero, compute as
+	 x * y + z.  */
+      if (u.ieee.exponent == 0x7fff
+	  || v.ieee.exponent == 0x7fff
+	  || w.ieee.exponent == 0x7fff
+	  || x == 0
+	  || y == 0)
+	return x * y + z;
+      /* If fma will certainly overflow, compute as x * y.  */
+      if (u.ieee.exponent + v.ieee.exponent
+	  > 0x7fff + IEEE854_LONG_DOUBLE_BIAS)
+	return x * y;
+      /* If x * y is less than 1/4 of LDBL_TRUE_MIN, neither the
+	 result nor whether there is underflow depends on its exact
+	 value, only on its sign.  */
+      if (u.ieee.exponent + v.ieee.exponent
+	  < IEEE854_LONG_DOUBLE_BIAS - LDBL_MANT_DIG - 2)
+	{
+	  int neg = u.ieee.negative ^ v.ieee.negative;
+	  _Float128 tiny = neg ? L(-0x1p-16494) : L(0x1p-16494);
+	  if (w.ieee.exponent >= 3)
+	    return tiny + z;
+	  /* Scaling up, adding TINY and scaling down produces the
+	     correct result, because in round-to-nearest mode adding
+	     TINY has no effect and in other modes double rounding is
+	     harmless.  But it may not produce required underflow
+	     exceptions.  */
+	  v.d = z * L(0x1p114) + tiny;
+	  if (TININESS_AFTER_ROUNDING
+	      ? v.ieee.exponent < 115
+	      : (w.ieee.exponent == 0
+		 || (w.ieee.exponent == 1
+		     && w.ieee.negative != neg
+		     && w.ieee.mantissa3 == 0
+		     && w.ieee.mantissa2 == 0
+		     && w.ieee.mantissa1 == 0
+		     && w.ieee.mantissa0 == 0)))
+	    {
+	      _Float128 force_underflow = x * y;
+	      math_force_eval (force_underflow);
+	    }
+	  return v.d * L(0x1p-114);
+	}
+      if (u.ieee.exponent + v.ieee.exponent
+	  >= 0x7fff + IEEE854_LONG_DOUBLE_BIAS - LDBL_MANT_DIG)
+	{
+	  /* Compute 1p-113 times smaller result and multiply
+	     at the end.  */
+	  if (u.ieee.exponent > v.ieee.exponent)
+	    u.ieee.exponent -= LDBL_MANT_DIG;
+	  else
+	    v.ieee.exponent -= LDBL_MANT_DIG;
+	  /* If x + y exponent is very large and z exponent is very small,
+	     it doesn't matter if we don't adjust it.  */
+	  if (w.ieee.exponent > LDBL_MANT_DIG)
+	    w.ieee.exponent -= LDBL_MANT_DIG;
+	  adjust = 1;
+	}
+      else if (w.ieee.exponent >= 0x7fff - LDBL_MANT_DIG)
+	{
+	  /* Similarly.
+	     If z exponent is very large and x and y exponents are
+	     very small, adjust them up to avoid spurious underflows,
+	     rather than down.  */
+	  if (u.ieee.exponent + v.ieee.exponent
+	      <= IEEE854_LONG_DOUBLE_BIAS + 2 * LDBL_MANT_DIG)
+	    {
+	      if (u.ieee.exponent > v.ieee.exponent)
+		u.ieee.exponent += 2 * LDBL_MANT_DIG + 2;
+	      else
+		v.ieee.exponent += 2 * LDBL_MANT_DIG + 2;
+	    }
+	  else if (u.ieee.exponent > v.ieee.exponent)
+	    {
+	      if (u.ieee.exponent > LDBL_MANT_DIG)
+		u.ieee.exponent -= LDBL_MANT_DIG;
+	    }
+	  else if (v.ieee.exponent > LDBL_MANT_DIG)
+	    v.ieee.exponent -= LDBL_MANT_DIG;
+	  w.ieee.exponent -= LDBL_MANT_DIG;
+	  adjust = 1;
+	}
+      else if (u.ieee.exponent >= 0x7fff - LDBL_MANT_DIG)
+	{
+	  u.ieee.exponent -= LDBL_MANT_DIG;
+	  if (v.ieee.exponent)
+	    v.ieee.exponent += LDBL_MANT_DIG;
+	  else
+	    v.d *= L(0x1p113);
+	}
+      else if (v.ieee.exponent >= 0x7fff - LDBL_MANT_DIG)
+	{
+	  v.ieee.exponent -= LDBL_MANT_DIG;
+	  if (u.ieee.exponent)
+	    u.ieee.exponent += LDBL_MANT_DIG;
+	  else
+	    u.d *= L(0x1p113);
+	}
+      else /* if (u.ieee.exponent + v.ieee.exponent
+		  <= IEEE854_LONG_DOUBLE_BIAS + LDBL_MANT_DIG) */
+	{
+	  if (u.ieee.exponent > v.ieee.exponent)
+	    u.ieee.exponent += 2 * LDBL_MANT_DIG + 2;
+	  else
+	    v.ieee.exponent += 2 * LDBL_MANT_DIG + 2;
+	  if (w.ieee.exponent <= 4 * LDBL_MANT_DIG + 6)
+	    {
+	      if (w.ieee.exponent)
+		w.ieee.exponent += 2 * LDBL_MANT_DIG + 2;
+	      else
+		w.d *= L(0x1p228);
+	      adjust = -1;
+	    }
+	  /* Otherwise x * y should just affect inexact
+	     and nothing else.  */
+	}
+      x = u.d;
+      y = v.d;
+      z = w.d;
+    }
+
+  /* Ensure correct sign of exact 0 + 0.  */
+  if (__glibc_unlikely ((x == 0 || y == 0) && z == 0))
+    {
+      x = math_opt_barrier (x);
+      return x * y + z;
+    }
+
+  fenv_t env;
+  feholdexcept (&env);
+  fesetround (FE_TONEAREST);
+
+  /* Multiplication m1 + m2 = x * y using Dekker's algorithm.  */
+#define C ((1LL << (LDBL_MANT_DIG + 1) / 2) + 1)
+  _Float128 x1 = x * C;
+  _Float128 y1 = y * C;
+  _Float128 m1 = x * y;
+  x1 = (x - x1) + x1;
+  y1 = (y - y1) + y1;
+  _Float128 x2 = x - x1;
+  _Float128 y2 = y - y1;
+  _Float128 m2 = (((x1 * y1 - m1) + x1 * y2) + x2 * y1) + x2 * y2;
+
+  /* Addition a1 + a2 = z + m1 using Knuth's algorithm.  */
+  _Float128 a1 = z + m1;
+  _Float128 t1 = a1 - z;
+  _Float128 t2 = a1 - t1;
+  t1 = m1 - t1;
+  t2 = z - t2;
+  _Float128 a2 = t1 + t2;
+  /* Ensure the arithmetic is not scheduled after feclearexcept call.  */
+  math_force_eval (m2);
+  math_force_eval (a2);
+  feclearexcept (FE_INEXACT);
+
+  /* If the result is an exact zero, ensure it has the correct sign.  */
+  if (a1 == 0 && m2 == 0)
+    {
+      feupdateenv (&env);
+      /* Ensure that round-to-nearest value of z + m1 is not reused.  */
+      z = math_opt_barrier (z);
+      return z + m1;
+    }
+
+  fesetround (FE_TOWARDZERO);
+  /* Perform m2 + a2 addition with round to odd.  */
+  u.d = a2 + m2;
+
+  if (__glibc_likely (adjust == 0))
+    {
+      if ((u.ieee.mantissa3 & 1) == 0 && u.ieee.exponent != 0x7fff)
+	u.ieee.mantissa3 |= fetestexcept (FE_INEXACT) != 0;
+      feupdateenv (&env);
+      /* Result is a1 + u.d.  */
+      return a1 + u.d;
+    }
+  else if (__glibc_likely (adjust > 0))
+    {
+      if ((u.ieee.mantissa3 & 1) == 0 && u.ieee.exponent != 0x7fff)
+	u.ieee.mantissa3 |= fetestexcept (FE_INEXACT) != 0;
+      feupdateenv (&env);
+      /* Result is a1 + u.d, scaled up.  */
+      return (a1 + u.d) * L(0x1p113);
+    }
+  else
+    {
+      if ((u.ieee.mantissa3 & 1) == 0)
+	u.ieee.mantissa3 |= fetestexcept (FE_INEXACT) != 0;
+      v.d = a1 + u.d;
+      /* Ensure the addition is not scheduled after fetestexcept call.  */
+      math_force_eval (v.d);
+      int j = fetestexcept (FE_INEXACT) != 0;
+      feupdateenv (&env);
+      /* Ensure the following computations are performed in default rounding
+	 mode instead of just reusing the round to zero computation.  */
+      asm volatile ("" : "=m" (u) : "m" (u));
+      /* If a1 + u.d is exact, the only rounding happens during
+	 scaling down.  */
+      if (j == 0)
+	return v.d * L(0x1p-228);
+      /* If result rounded to zero is not subnormal, no double
+	 rounding will occur.  */
+      if (v.ieee.exponent > 228)
+	return (a1 + u.d) * L(0x1p-228);
+      /* If v.d * 0x1p-228L with round to zero is a subnormal above
+	 or equal to LDBL_MIN / 2, then v.d * 0x1p-228L shifts mantissa
+	 down just by 1 bit, which means v.ieee.mantissa3 |= j would
+	 change the round bit, not sticky or guard bit.
+	 v.d * 0x1p-228L never normalizes by shifting up,
+	 so round bit plus sticky bit should be already enough
+	 for proper rounding.  */
+      if (v.ieee.exponent == 228)
+	{
+	  /* If the exponent would be in the normal range when
+	     rounding to normal precision with unbounded exponent
+	     range, the exact result is known and spurious underflows
+	     must be avoided on systems detecting tininess after
+	     rounding.  */
+	  if (TININESS_AFTER_ROUNDING)
+	    {
+	      w.d = a1 + u.d;
+	      if (w.ieee.exponent == 229)
+		return w.d * L(0x1p-228);
+	    }
+	  /* v.ieee.mantissa3 & 2 is LSB bit of the result before rounding,
+	     v.ieee.mantissa3 & 1 is the round bit and j is our sticky
+	     bit.  */
+	  w.d = 0;
+	  w.ieee.mantissa3 = ((v.ieee.mantissa3 & 3) << 1) | j;
+	  w.ieee.negative = v.ieee.negative;
+	  v.ieee.mantissa3 &= ~3U;
+	  v.d *= L(0x1p-228);
+	  w.d *= L(0x1p-2);
+	  return v.d + w.d;
+	}
+      v.ieee.mantissa3 |= j;
+      return v.d * L(0x1p-228);
+    }
+}
+weak_alias (__fmal, fmal)