x86: Use one ldbl2mpn.c file for both i386 and x86_64

1 files changed, 120 insertions, 0 deletions

diff --git a/sysdeps/x86/ldbl2mpn.c b/sysdeps/x86/ldbl2mpn.c
new file mode 100644
index 0000000000..ec8464eef7
--- /dev/null
+++ b/sysdeps/x86/ldbl2mpn.c
@@ -0,0 +1,120 @@
+/* Copyright (C) 1995-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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
+   <https://www.gnu.org/licenses/>.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+#include <ieee754.h>
+#include <float.h>
+#include <stdlib.h>
+
+/* Convert a `long double' in IEEE854 standard double-precision format to a
+   multi-precision integer representing the significand scaled up by its
+   number of bits (64 for long double) and an integral power of two
+   (MPN frexpl). */
+
+mp_size_t
+__mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size,
+			   int *expt, int *is_neg,
+			   long double value)
+{
+  union ieee854_long_double u;
+  u.d = value;
+
+  *is_neg = u.ieee.negative;
+  *expt = (int) u.ieee.exponent - IEEE854_LONG_DOUBLE_BIAS;
+
+#if BITS_PER_MP_LIMB == 32
+  res_ptr[0] = u.ieee.mantissa1; /* Low-order 32 bits of fraction.  */
+  res_ptr[1] = u.ieee.mantissa0; /* High-order 32 bits.  */
+  #define N 2
+#elif BITS_PER_MP_LIMB == 64
+  /* Hopefully the compiler will combine the two bitfield extracts
+     and this composition into just the original quadword extract.  */
+  res_ptr[0] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1;
+  #define N 1
+#else
+  #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
+#endif
+
+  if (u.ieee.exponent == 0)
+    {
+      /* A biased exponent of zero is a special case.
+	 Either it is a zero or it is a denormal number.  */
+      if (res_ptr[0] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=2.  */
+	/* It's zero.  */
+	*expt = 0;
+      else
+	{
+	  /* It is a denormal number, meaning it has no implicit leading
+	     one bit, and its exponent is in fact the format minimum.  */
+	  int cnt;
+
+	  /* One problem with Intel's 80-bit format is that the explicit
+	     leading one in the normalized representation has to be zero
+	     for denormalized number.  If it is one, the number is according
+	     to Intel's specification an invalid number.  We make the
+	     representation unique by explicitly clearing this bit.  */
+	  res_ptr[N - 1] &= ~((mp_limb_t) 1 << ((LDBL_MANT_DIG - 1) % BITS_PER_MP_LIMB));
+
+	  if (res_ptr[N - 1] != 0)
+	    {
+	      count_leading_zeros (cnt, res_ptr[N - 1]);
+	      if (cnt != 0)
+		{
+#if N == 2
+		  res_ptr[N - 1] = res_ptr[N - 1] << cnt
+				   | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));
+		  res_ptr[0] <<= cnt;
+#else
+		  res_ptr[N - 1] <<= cnt;
+#endif
+		}
+	      *expt = LDBL_MIN_EXP - 1 - cnt;
+	    }
+	  else if (res_ptr[0] != 0)
+	    {
+	      count_leading_zeros (cnt, res_ptr[0]);
+	      res_ptr[N - 1] = res_ptr[0] << cnt;
+	      res_ptr[0] = 0;
+	      *expt = LDBL_MIN_EXP - 1 - BITS_PER_MP_LIMB - cnt;
+	    }
+	  else
+	    {
+	      /* This is the special case of the pseudo denormal number
+		 with only the implicit leading bit set.  The value is
+		 in fact a normal number and so we have to treat this
+		 case differently.  */
+#if N == 2
+	      res_ptr[N - 1] = 0x80000000ul;
+#else
+	      res_ptr[0] = 0x8000000000000000ul;
+#endif
+	      *expt = LDBL_MIN_EXP - 1;
+	    }
+	}
+    }
+  else if (u.ieee.exponent < 0x7fff
+#if N == 2
+	   && res_ptr[0] == 0
+#endif
+	   && res_ptr[N - 1] == 0)
+    /* Pseudo zero.  */
+    *expt = 0;
+
+  return N;
+}