Improve saturated_cast performance

base/numerics/safe_numerics_unittest.cc

 // Copyright 2013 The Chromium 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 <stddef.h>
 #include <stdint.h>
 
 #include <limits>
 #include <type_traits>
 
@@ skipping 653 matching lines @@
 
     const CheckedNumeric<Dst> checked_dst;
     TEST_EXPECTED_VALUE(1, checked_dst + static_cast<Src>(1));
     TEST_EXPECTED_FAILURE(checked_dst + SrcLimits::max());
     TEST_EXPECTED_FAILURE(checked_dst + static_cast<Src>(-1));
     TEST_EXPECTED_FAILURE(checked_dst + SrcLimits::lowest());
 
     TEST_EXPECTED_RANGE(RANGE_OVERFLOW, SrcLimits::max());
     TEST_EXPECTED_RANGE(RANGE_VALID, static_cast<Src>(1));
     TEST_EXPECTED_RANGE(RANGE_UNDERFLOW, static_cast<Src>(-1));
+
+    // Additional saturation tests.
+    EXPECT_EQ(DstLimits::max(), saturated_cast<Dst>(SrcLimits::max()));
+    EXPECT_EQ(DstLimits::lowest(), saturated_cast<Dst>(SrcLimits::lowest()));
+
     if (SrcLimits::is_iec559) {
+      EXPECT_EQ(Dst(0), saturated_cast<Dst>(SrcLimits::quiet_NaN()));
+
       TEST_EXPECTED_RANGE(RANGE_UNDERFLOW, SrcLimits::max() * -1);
       TEST_EXPECTED_RANGE(RANGE_OVERFLOW, SrcLimits::infinity());
       TEST_EXPECTED_RANGE(RANGE_UNDERFLOW, SrcLimits::infinity() * -1);
       TEST_EXPECTED_RANGE(RANGE_INVALID, SrcLimits::quiet_NaN());
       if (DstLimits::is_integer) {
         if (SrcLimits::digits < DstLimits::digits) {
           TEST_EXPECTED_RANGE(RANGE_OVERFLOW,
                               static_cast<Src>(DstLimits::max()));
         } else {
           TEST_EXPECTED_RANGE(RANGE_VALID, static_cast<Src>(DstLimits::max()));
@@ skipping 22 matching lines @@
     TestStrictComparison<Dst, Src>();
 
     const CheckedNumeric<Dst> checked_dst;
     TEST_EXPECTED_VALUE(1, checked_dst + static_cast<Src>(1));
     TEST_EXPECTED_FAILURE(checked_dst + SrcLimits::max());
     TEST_EXPECTED_VALUE(SrcLimits::lowest(), checked_dst + SrcLimits::lowest());
 
     TEST_EXPECTED_RANGE(RANGE_VALID, SrcLimits::lowest());
     TEST_EXPECTED_RANGE(RANGE_OVERFLOW, SrcLimits::max());
     TEST_EXPECTED_RANGE(RANGE_VALID, static_cast<Src>(1));
+
+    // Additional saturation tests.
+    EXPECT_EQ(DstLimits::max(), saturated_cast<Dst>(SrcLimits::max()));
+    EXPECT_EQ(Dst(0), saturated_cast<Dst>(SrcLimits::lowest()));
   }
 };
 
 // Helper macro to wrap displaying the conversion types and line numbers
 #define TEST_NUMERIC_CONVERSION(d, s, t) \
   TestNumericConversion<d, s, t>::Test(#d, #s, __LINE__)
 
 TEST(SafeNumerics, IntMinOperations) {
   TEST_NUMERIC_CONVERSION(int8_t, int8_t, SIGN_PRESERVING_VALUE_PRESERVING);
   TEST_NUMERIC_CONVERSION(uint8_t, uint8_t, SIGN_PRESERVING_VALUE_PRESERVING);
@@ skipping 367 matching lines @@
   EXPECT_EQ(static_cast<decltype(d)::type>(-.5), d);
   auto e = CheckMod(MakeCheckedNum(20), 3).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(e)::type>(2), e);
   auto f = CheckLsh(1, MakeCheckedNum(2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(f)::type>(4), f);
   auto g = CheckRsh(4, MakeCheckedNum(2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(g)::type>(1), g);
   auto h = CheckRsh(CheckAdd(1, 1, 1, 1), CheckSub(4, 2)).ValueOrDie();
   EXPECT_EQ(static_cast<decltype(h)::type>(1), h);
 }