[ieee754] Slightly improve unittests for exp/log.

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"
 
 using testing::BitEq;
 using testing::IsNaN;
 
 namespace v8 {
 namespace base {
 namespace ieee754 {
 
 namespace {
 
+double const kE = 2.718281828459045;
 double const kPI = 3.141592653589793;
 double const kTwo120 = 1.329227995784916e+36;
 
 }  // namespace
 
 TEST(Ieee754, Atan) {
   EXPECT_THAT(atan(std::numeric_limits<double>::quiet_NaN()), IsNaN());
   EXPECT_THAT(atan(std::numeric_limits<double>::signaling_NaN()), IsNaN());
   EXPECT_THAT(atan(-0.0), BitEq(-0.0));
   EXPECT_THAT(atan(0.0), BitEq(0.0));
@@ skipping 91 matching lines @@
   EXPECT_EQ(0.0, exp(-std::numeric_limits<double>::infinity()));
   EXPECT_EQ(0.0, exp(-1000));
   EXPECT_EQ(0.0, exp(-745.1332191019412));
   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));
+
+  // Test that exp(x) is monotonic near 1.
   EXPECT_GE(exp(1.0), exp(0.9999999999999999));
   EXPECT_LE(exp(1.0), exp(1.0000000000000002));
-  EXPECT_EQ(2.718281828459045, exp(1.0));
+
+  // Test that we produce the correctly rounded result for 1.
+  EXPECT_EQ(kE, 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()));
@@ skipping 16 matching lines @@
 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()));
+
+  // Test that log(E) produces the correctly rounded result.
+  EXPECT_EQ(1.0, log(kE));
 }
 
 TEST(Ieee754, Log1p) {
   EXPECT_THAT(log1p(std::numeric_limits<double>::quiet_NaN()), IsNaN());
   EXPECT_THAT(log1p(std::numeric_limits<double>::signaling_NaN()), IsNaN());
   EXPECT_THAT(log1p(-std::numeric_limits<double>::infinity()), IsNaN());
   EXPECT_EQ(-std::numeric_limits<double>::infinity(), log1p(-1.0));
   EXPECT_EQ(0.0, log1p(0.0));
   EXPECT_EQ(-0.0, log1p(-0.0));
   EXPECT_EQ(std::numeric_limits<double>::infinity(),
@@ skipping 124 matching lines @@
   EXPECT_EQ(2.910566692924059e11, tan(1048575.0 / 2.0 * kPI));
 
   // Test Hayne-Panek reduction.
   EXPECT_EQ(-0.40806638884180424e0, tan(kTwo120));
   EXPECT_EQ(0.40806638884180424e0, tan(-kTwo120));
 }
 
 }  // namespace ieee754
 }  // namespace base
 }  // namespace v8