[builtins] Introduce proper Float64Exp operator.

test/unittests/base/ieee754-unittest.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <limits>
 
 #include "src/base/ieee754.h"
 #include "src/base/macros.h"
 #include "testing/gmock-support.h"
 #include "testing/gtest-support.h"
@@ skipping 36 matching lines @@
                    atan2(std::numeric_limits<double>::infinity(),
                          -std::numeric_limits<double>::infinity()));
   EXPECT_DOUBLE_EQ(-0.7853981633974483,
                    atan2(-std::numeric_limits<double>::infinity(),
                          std::numeric_limits<double>::infinity()));
   EXPECT_DOUBLE_EQ(-2.356194490192345,
                    atan2(-std::numeric_limits<double>::infinity(),
                          -std::numeric_limits<double>::infinity()));
 }
 
+TEST(Ieee754, Exp) {
+  EXPECT_THAT(exp(std::numeric_limits<double>::quiet_NaN()), IsNaN());
+  EXPECT_THAT(exp(std::numeric_limits<double>::signaling_NaN()), IsNaN());
+  EXPECT_EQ(0.0, exp(-std::numeric_limits<double>::infinity()));
+  EXPECT_EQ(0.0, exp(-1000));
+  EXPECT_EQ(0.0, exp(-745.1332191019412));

[Raymond Toy, 2016/06/16 18:12:44]

DBC:  It might be useful to add comments on what these tests are actually doing.
 At a glance, they just look like lots of random numbers, but they have specific
meanings and are testing certain behaviors. 

[Benedikt Meurer, 2016/06/16 18:13:53]

May we ask you for help on these and the other fdlibm function tests? You seem
to have a lot more background here.

[Raymond Toy, 2016/06/16 18:34:30]

No problem.  I'll look into them shortly.  I see that I was also pretty sloppy
about documenting the tests that I wrote. It will take some time.

But don't let this block landing these changes!

+  EXPECT_EQ(2.2250738585072626e-308, exp(-708.39641853226408));
+  EXPECT_EQ(3.307553003638408e-308, exp(-708.0));
+  EXPECT_EQ(4.9406564584124654e-324, exp(-7.45133219101941108420e+02));
+  EXPECT_EQ(0.36787944117144233, exp(-1.0));
+  EXPECT_EQ(1.0, exp(-0.0));
+  EXPECT_EQ(1.0, exp(0.0));
+  EXPECT_EQ(1.0, exp(2.2250738585072014e-308));
+  EXPECT_GE(exp(1.0), exp(0.9999999999999999));
+  EXPECT_LE(exp(1.0), exp(1.0000000000000002));
+  EXPECT_EQ(2.7182818284590455, exp(1.0));
+  EXPECT_EQ(7.38905609893065e0, exp(2.0));
+  EXPECT_EQ(1.7976931348622732e308, exp(7.09782712893383973096e+02));
+  EXPECT_EQ(2.6881171418161356e+43, exp(100.0));
+  EXPECT_EQ(8.218407461554972e+307, exp(709.0));
+  EXPECT_EQ(1.7968190737295725e308, exp(709.7822265625e0));
+  EXPECT_EQ(std::numeric_limits<double>::infinity(), exp(709.7827128933841e0));
+  EXPECT_EQ(std::numeric_limits<double>::infinity(), exp(710.0));
+  EXPECT_EQ(std::numeric_limits<double>::infinity(), exp(1000.0));
+  EXPECT_EQ(std::numeric_limits<double>::infinity(),
+            exp(std::numeric_limits<double>::infinity()));
+}
+
 TEST(Ieee754, Log) {
   EXPECT_THAT(log(std::numeric_limits<double>::quiet_NaN()), IsNaN());
   EXPECT_THAT(log(std::numeric_limits<double>::signaling_NaN()), IsNaN());
   EXPECT_THAT(log(-std::numeric_limits<double>::infinity()), IsNaN());
   EXPECT_THAT(log(-1.0), IsNaN());
   EXPECT_EQ(-std::numeric_limits<double>::infinity(), log(-0.0));
   EXPECT_EQ(-std::numeric_limits<double>::infinity(), log(0.0));
   EXPECT_EQ(0.0, log(1.0));
   EXPECT_EQ(std::numeric_limits<double>::infinity(),
             log(std::numeric_limits<double>::infinity()));
@@ skipping 47 matching lines @@
   EXPECT_EQ(3.0, log10(1000.0));
   EXPECT_EQ(14.0, log10(100000000000000));  // log10(10 ^ 14)
   EXPECT_EQ(3.7389561269540406, log10(5482.2158));
   EXPECT_EQ(14.661551142893833, log10(458723662312872.125782332587));
   EXPECT_EQ(-0.9083828622192334, log10(0.12348583358871));
 }
 
 }  // namespace ieee754
 }  // namespace base
 }  // namespace v8