Revert "Remove gmp from AOS"

This reverts commit f37c97684f0910a3f241394549392f00145ab0f7.

We need gmp for SymEngine for symbolicmanipultion in C++

Change-Id: Ia13216d1715cf96944f7b4f422b7a799f921d4a4
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/third_party/gmp/mpf/mul.c b/third_party/gmp/mpf/mul.c
new file mode 100644
index 0000000..3099461
--- /dev/null
+++ b/third_party/gmp/mpf/mul.c
@@ -0,0 +1,134 @@
+/* mpf_mul -- Multiply two floats.
+
+Copyright 1993, 1994, 1996, 2001, 2005, 2019 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+  * the GNU Lesser General Public License as published by the Free
+    Software Foundation; either version 3 of the License, or (at your
+    option) any later version.
+
+or
+
+  * the GNU General Public License as published by the Free Software
+    Foundation; either version 2 of the License, or (at your option) any
+    later version.
+
+or both in parallel, as here.
+
+The GNU MP 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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library.  If not,
+see https://www.gnu.org/licenses/.  */
+
+#include "gmp-impl.h"
+
+void
+mpf_mul (mpf_ptr r, mpf_srcptr u, mpf_srcptr v)
+{
+  mp_size_t sign_product;
+  mp_size_t prec = r->_mp_prec;
+  mp_size_t rsize;
+  mp_limb_t cy_limb;
+  mp_ptr rp, tp;
+  mp_size_t adj;
+  TMP_DECL;
+
+  if (u == v)
+    {
+      mp_srcptr up;
+      mp_size_t usize;
+
+      usize = u->_mp_size;
+      sign_product = 0;
+
+      usize = ABS (usize);
+
+      up = u->_mp_d;
+      if (usize > prec)
+	{
+	  up += usize - prec;
+	  usize = prec;
+	}
+
+      if (usize == 0)
+	{
+	  r->_mp_size = 0;
+	  r->_mp_exp = 0;		/* ??? */
+	  return;
+	}
+      else
+	{
+	  TMP_MARK;
+	  rsize = 2 * usize;
+	  tp = TMP_ALLOC_LIMBS (rsize);
+
+	  mpn_sqr (tp, up, usize);
+	  cy_limb = tp[rsize - 1];
+	}
+    }
+  else
+    {
+      mp_srcptr up, vp;
+      mp_size_t usize, vsize;
+
+      usize = u->_mp_size;
+      vsize = v->_mp_size;
+      sign_product = usize ^ vsize;
+
+      usize = ABS (usize);
+      vsize = ABS (vsize);
+
+      up = u->_mp_d;
+      vp = v->_mp_d;
+      if (usize > prec)
+	{
+	  up += usize - prec;
+	  usize = prec;
+	}
+      if (vsize > prec)
+	{
+	  vp += vsize - prec;
+	  vsize = prec;
+	}
+
+      if (usize == 0 || vsize == 0)
+	{
+	  r->_mp_size = 0;
+	  r->_mp_exp = 0;
+	  return;
+	}
+      else
+	{
+	  TMP_MARK;
+	  rsize = usize + vsize;
+	  tp = TMP_ALLOC_LIMBS (rsize);
+	  cy_limb = (usize >= vsize
+		     ? mpn_mul (tp, up, usize, vp, vsize)
+		     : mpn_mul (tp, vp, vsize, up, usize));
+
+	}
+    }
+
+  adj = cy_limb == 0;
+  rsize -= adj;
+  prec++;
+  if (rsize > prec)
+    {
+      tp += rsize - prec;
+      rsize = prec;
+    }
+  rp = r->_mp_d;
+  MPN_COPY (rp, tp, rsize);
+  r->_mp_exp = u->_mp_exp + v->_mp_exp - adj;
+  r->_mp_size = sign_product >= 0 ? rsize : -rsize;
+
+  TMP_FREE;
+}