Rename jerry-libm to jerry-math (#4410)

That "libm" in the name of the library resulted in awkward naming
on *nix systems (`libjerry-libm.*`, "lib" occurring twice). And the
name of the corresponding header is `math.h` anyway.

Note that this is a breaking change in some sense. The commit
contains no API change, but the build system does change for users
of the math library.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-math/nextafter.c

@@ -0,0 +1,135 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * This file is based on work under the following copyright and permission
+ * notice:
+ *
+ *     Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ *     Developed at SunSoft, a Sun Microsystems, Inc. business.
+ *     Permission to use, copy, modify, and distribute this
+ *     software is freely granted, provided that this notice
+ *     is preserved.
+ *
+ *     @(#)s_nextafter.c 1.3 95/01/18
+ */
+
+#include "jerry-math-internal.h"
+
+double
+nextafter (double x,
+           double y)
+{
+  int hx, hy, ix, iy;
+  unsigned lx, ly;
+  double_accessor ret;
+
+  hx = __HI (x); /* high word of x */
+  lx = __LO (x); /* low  word of x */
+  hy = __HI (y); /* high word of y */
+  ly = __LO (y); /* low  word of y */
+  ix = hx & 0x7fffffff; /* |x| */
+  iy = hy & 0x7fffffff; /* |y| */
+
+  if (((ix >= 0x7ff00000) && ((ix - 0x7ff00000) | lx) != 0)     /* x is nan */
+      || ((iy >= 0x7ff00000) && ((iy - 0x7ff00000) | ly) != 0)) /* y is nan */
+  {
+    return x + y;
+  }
+
+  if (x == y)
+  {
+    return x; /* x=y, return x */
+  }
+
+  if ((ix | lx) == 0)
+  { /* x == 0 */
+    ret.as_int.hi = hy & 0x80000000; /* return +-minsubnormal */
+    ret.as_int.lo = 1;
+    y = ret.dbl * ret.dbl;
+    if (y == ret.dbl)
+    {
+      return y;
+    }
+    else
+    {
+      return ret.dbl; /* raise underflow flag */
+    }
+  }
+
+  if (hx >= 0)
+  { /* x > 0 */
+    if (hx > hy || ((hx == hy) && (lx > ly)))
+    { /* x > y, x -= ulp */
+      if (lx == 0)
+      {
+        hx -= 1;
+      }
+
+      lx -= 1;
+    }
+    else
+    { /* x < y, x += ulp */
+      lx += 1;
+
+      if (lx == 0)
+      {
+        hx += 1;
+      }
+    }
+  }
+  else
+  { /* x < 0 */
+    if (hy >= 0 || hx > hy || ((hx == hy) && (lx > ly)))
+    { /* x < y, x -= ulp */
+      if (lx == 0)
+      {
+        hx -= 1;
+      }
+
+      lx -= 1;
+    }
+    else
+    { /* x > y, x += ulp */
+      lx += 1;
+
+      if (lx == 0)
+      {
+        hx += 1;
+      }
+    }
+  }
+
+  hy = hx & 0x7ff00000;
+
+  if (hy >= 0x7ff00000)
+  {
+    return x + x; /* overflow */
+  }
+
+  if (hy < 0x00100000)
+  { /* underflow */
+    y = x * x;
+    if (y != x)
+    { /* raise underflow flag */
+      ret.as_int.hi = hx;
+      ret.as_int.lo = lx;
+      return ret.dbl;
+    }
+  }
+
+  ret.as_int.hi = hx;
+  ret.as_int.lo = lx;
+  return ret.dbl;
+} /* nextafter */