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/scalbn.c

@@ -0,0 +1,99 @@
+/* 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_scalbn.c 1.3 95/01/18
+ */
+
+#include "jerry-math-internal.h"
+
+/* scalbn(x,n) returns x* 2**n  computed by  exponent
+ * manipulation rather than by actually performing an
+ * exponentiation or a multiplication.
+ */
+
+#define two54  1.80143985094819840000e+16 /* 0x43500000, 0x00000000 */
+#define twom54 5.55111512312578270212e-17 /* 0x3C900000, 0x00000000 */
+#define huge   1.0e+300
+#define tiny   1.0e-300
+
+double
+scalbn (double x, int n)
+{
+  int k, hx, lx;
+
+  hx = __HI (x);
+  lx = __LO (x);
+  k = (hx & 0x7ff00000) >> 20; /* extract exponent */
+  if (k == 0) /* 0 or subnormal x */
+  {
+    if ((lx | (hx & 0x7fffffff)) == 0) /* +-0 */
+    {
+      return x;
+    }
+    x *= two54;
+    hx = __HI (x);
+    k = ((hx & 0x7ff00000) >> 20) - 54;
+    if (n < -50000) /*underflow */
+    {
+      return tiny * x;
+    }
+  }
+  if (k == 0x7ff) /* NaN or Inf */
+  {
+    return x + x;
+  }
+  k = k + n;
+  if (k > 0x7fe) /* overflow  */
+  {
+    return huge * copysign (huge, x);
+  }
+  if (k > 0) /* normal result */
+  {
+    double_accessor ret;
+    ret.dbl = x;
+    ret.as_int.hi = (hx & 0x800fffff) | (k << 20);
+    return ret.dbl;
+  }
+  if (k <= -54)
+  {
+    if (n > 50000) /* in case integer overflow in n + k */
+    {
+      return huge * copysign (huge, x); /*overflow */
+    }
+    else
+    {
+      return tiny * copysign (tiny, x); /*underflow */
+    }
+  }
+  k += 54; /* subnormal result */
+  double_accessor ret;
+  ret.dbl = x;
+  ret.as_int.hi = (hx & 0x800fffff) | (k << 20);
+  return ret.dbl * twom54;
+} /* scalbn */
+
+#undef two54
+#undef twom54
+#undef huge
+#undef tiny