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Fixing Math.pow

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The Math.pow implementation relies on libm's pow. However, the ISO C
and ES5.1 standards differ on pow:
  * `x ** NAN` is NAN in ES but `+1 ** y` is 1 in C
  * `+-1 ** +-INF` is NAN in ES but 1 in C

This patch:
  * Modifies the Math.pow implementation to handle the special cases
    instead calling pow.
  * Adds a test case to jerry-test-suite as it did not test
    `Math.pow(1,NaN)`.
  * Fixes jerry-libm's pow, as it was not standard conforming, which
    helped hiding the error in Math.pow.
  * Updates the unit test for libm.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu
This commit is contained in:
Akos Kiss 2016-08-10 16:24:12 +02:00
parent 8f76bab92e
commit 9d4f7c917f
5 changed files with 41 additions and 6 deletions
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11
jerry-core/ecma/builtin-objects/ecma-builtin-math.c
View File

@ -477,7 +477,16 @@ ecma_builtin_math_object_pow (ecma_value_t this_arg, /**< 'this' argument */
ECMA_OP_TO_NUMBER_TRY_CATCH (x, arg1, ret_value);
ECMA_OP_TO_NUMBER_TRY_CATCH (y, arg2, ret_value);
ret_value = ecma_make_number_value (DOUBLE_TO_ECMA_NUMBER_T (pow (x, y)));
if (ecma_number_is_nan (y) ||
(ecma_number_is_infinity (y) && (x == 1.0 || x == -1.0)))
{
/* Handle differences between ES5.1 and ISO C standards for pow. */
ret_value = ecma_make_number_value (ecma_number_make_nan ());
}
else
{
ret_value = ecma_make_number_value (DOUBLE_TO_ECMA_NUMBER_T (pow (x, y)));
}
ECMA_OP_TO_NUMBER_FINALIZE (y);
ECMA_OP_TO_NUMBER_FINALIZE (x);

13
jerry-libm/pow.c
View File

@ -39,6 +39,7 @@
* 3. Return x**y = 2**n*exp(y'*log2)
*
* Special cases:
* 0. +1 ** (anything) is 1
* 1. (anything) ** 0 is 1
* 2. (anything) ** 1 is itself
* 3. (anything) ** NAN is NAN
@ -47,7 +48,7 @@
* 6. +-(|x| > 1) ** -INF is +0
* 7. +-(|x| < 1) ** +INF is +0
* 8. +-(|x| < 1) ** -INF is +INF
* 9. +-1 ** +-INF is NAN
* 9. -1 ** +-INF is 1
* 10. +0 ** (+anything except 0, NAN) is +0
* 11. -0 ** (+anything except 0, NAN, odd integer) is +0
* 12. +0 ** (-anything except 0, NAN) is +INF
@ -133,6 +134,12 @@ pow (double x, double y)
ix = hx & 0x7fffffff;
iy = hy & 0x7fffffff;
/* x == one: 1**y = 1 */
if (((hx - 0x3ff00000) | lx) == 0)
{
return one;
}
/* y == zero: x**0 = 1 */
if ((iy | ly) == 0)
{
@ -184,9 +191,9 @@ pow (double x, double y)
{
if (iy == 0x7ff00000) /* y is +-inf */
{
if (((ix - 0x3ff00000) | lx) == 0) /* inf**+-1 is NaN */
if (((ix - 0x3ff00000) | lx) == 0) /* +-1**+-inf is 1 */
{
return y - y;
return one;
}
else if (ix >= 0x3ff00000) /* (|x|>1)**+-inf = inf,0 */
{

16
tests/jerry-test-suite/15/15.08/15.08.02/15.08.02.13/15.08.02.13-031.js Normal file
View File

@ -0,0 +1,16 @@
// Copyright 2016 Samsung Electronics Co., Ltd.
// Copyright 2016 University of Szeged
//
// 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.
assert(isNaN(Math.pow(1, NaN)));

5
tests/unit/test-libm.inc.h
View File

@ -330,6 +330,11 @@ check_double ("pow (1.0, 1.0)", pow (1.0, 1.0), 1.00000000000000000000E+00);
check_double ("pow (1.0, -1.0)", pow (1.0, -1.0), 1.00000000000000000000E+00);
check_double ("pow (-1.0, 1.0)", pow (-1.0, 1.0), -1.00000000000000000000E+00);
check_double ("pow (-1.0, -1.0)", pow (-1.0, -1.0), -1.00000000000000000000E+00);
check_double ("pow (1.0, INFINITY)", pow (1.0, INFINITY), 1.00000000000000000000E+00);
check_double ("pow (1.0, -INFINITY)", pow (1.0, -INFINITY), 1.00000000000000000000E+00);
check_double ("pow (-1.0, INFINITY)", pow (-1.0, INFINITY), 1.00000000000000000000E+00);
check_double ("pow (-1.0, -INFINITY)", pow (-1.0, -INFINITY), 1.00000000000000000000E+00);
check_double ("pow (1.0, NAN)", pow (1.0, NAN), 1.00000000000000000000E+00);
check_double ("pow (-1.0, NAN)", pow (-1.0, NAN), NAN);
check_double ("pow (INFINITY, 0.0)", pow (INFINITY, 0.0), 1.00000000000000000000E+00);
check_double ("pow (INFINITY, -0.0)", pow (INFINITY, -0.0), 1.00000000000000000000E+00);

2
tools/unit-tests/gen-test-libm.c
View File

@ -465,13 +465,11 @@ main (int argc, char **args)
GEN_DBL_TEST (pow (1.0, -1.0));
GEN_DBL_TEST (pow (-1.0, 1.0));
GEN_DBL_TEST (pow (-1.0, -1.0));
/* SKIPPED: reference libm implementation seems to (incorrectly?) result 1.0 instead of NAN
GEN_DBL_TEST (pow (1.0, INFINITY));
GEN_DBL_TEST (pow (1.0, -INFINITY));
GEN_DBL_TEST (pow (-1.0, INFINITY));
GEN_DBL_TEST (pow (-1.0, -INFINITY));
GEN_DBL_TEST (pow (1.0, NAN));
*/
GEN_DBL_TEST (pow (-1.0, NAN));
GEN_DBL_TEST (pow (INFINITY, 0.0));
GEN_DBL_TEST (pow (INFINITY, -0.0));