Implement missing Math logarithm functions from ES6 (#3617)

Math.log2, Math.log10, Math.log1p, Math.expm1 C implementation ported from fdlibm Part of Issue #3568 JerryScript-DCO-1.0-Signed-off-by: Rafal Walczyna r.walczyna@samsung.com
2020-04-04 02:00:41 +02:00
parent c74256ccba
commit e470b13096
13 changed files with 1124 additions and 16 deletions
@@ -0,0 +1,116 @@
+/* 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.
+ *
+ *     @(#)e_log10.c 1.3 95/01/18
+ */
+
+#include "jerry-libm-internal.h"
+
+/* log10(x)
+ * Return the base 10 logarithm of x
+ *
+ * Method :
+ *  Let log10_2hi = leading 40 bits of log10(2) and
+ *      log10_2lo = log10(2) - log10_2hi,
+ *      ivln10   = 1/log(10) rounded.
+ *  Then
+ *    n = ilogb(x),
+ *    if(n<0)  n = n+1;
+ *    x = scalbn(x,-n);
+ *    log10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x))
+ *
+ * Note 1:
+ *  To guarantee log10(10**n)=n, where 10**n is normal, the rounding
+ *  mode must set to Round-to-Nearest.
+ * Note 2:
+ *  [1/log(10)] rounded to 53 bits has error  .198   ulps;
+ *  log10 is monotonic at all binary break points.
+ *
+ * Special cases:
+ *  log10(x) is NaN with signal if x < 0;
+ *  log10(+INF) is +INF with no signal; log10(0) is -INF with signal;
+ *  log10(NaN) is that NaN with no signal;
+ *  log10(10**N) = N  for N=0,1,...,22.
+ *
+ * Constants:
+ * The hexadecimal values are the intended ones for the following constants.
+ * The decimal values may be used, provided that the compiler will convert
+ * from decimal to binary accurately enough to produce the hexadecimal values
+ * shown.
+ */
+
+#define zero 0.0
+#define two54 1.80143985094819840000e+16     /* 0x43500000, 0x00000000 */
+#define ivln10 4.34294481903251816668e-01    /* 0x3FDBCB7B, 0x1526E50E */
+#define log10_2hi 3.01029995663611771306e-01 /* 0x3FD34413, 0x509F6000 */
+#define log10_2lo 3.69423907715893078616e-13 /* 0x3D59FEF3, 0x11F12B36 */
+
+double
+log10 (double x)
+{
+  double y, z;
+  int i, k, hx;
+  unsigned lx;
+  double_accessor temp;
+
+  hx = __HI (x); /* high word of x */
+  lx = __LO (x); /* low word of x */
+
+  k = 0;
+  if (hx < 0x00100000)
+  {
+    /* x < 2**-1022  */
+    if (((hx & 0x7fffffff) | lx) == 0)
+    {
+      /* log(+-0)=-inf */
+      return -two54 / zero;
+    }
+    if (hx < 0)
+    {
+      /* log(-#) = NaN */
+      return (x - x) / zero;
+    }
+    k -= 54;
+    x *= two54;    /* subnormal number, scale up x */
+    hx = __HI (x); /* high word of x */
+  }
+  if (hx >= 0x7ff00000)
+  {
+    return x + x;
+  }
+  k += (hx >> 20) - 1023;
+  i = ((unsigned) k & 0x80000000) >> 31;
+  hx = (hx & 0x000fffff) | ((0x3ff - i) << 20);
+  y = (double) (k + i);
+  temp.dbl = x;
+  temp.as_int.hi = hx;
+  z = y * log10_2lo + ivln10 * log (temp.dbl);
+  return z + y * log10_2hi;
+} /* log10 */
+
+#undef zero
+#undef two54
+#undef ivln10
+#undef log10_2hi
+#undef log10_2lo