Add a test for SafeMath.

Change-Id: I445cd168e6f22a4c12f954eb94e32bd28dba9501

2 files changed, 133 insertions, 0 deletions

diff --git a/build/Android.gtest.mk b/build/Android.gtest.mk
index 63200b7848..00fbd6933b 100644
--- a/build/Android.gtest.mk
+++ b/build/Android.gtest.mk
@@ -111,6 +111,7 @@ RUNTIME_GTEST_COMMON_SRC_FILES := \
   runtime/indirect_reference_table_test.cc \
   runtime/instruction_set_test.cc \
   runtime/intern_table_test.cc \
+  runtime/interpreter/safe_math_test.cc \
   runtime/leb128_test.cc \
   runtime/mem_map_test.cc \
   runtime/mirror/dex_cache_test.cc \
diff --git a/runtime/interpreter/safe_math_test.cc b/runtime/interpreter/safe_math_test.cc
new file mode 100644
index 0000000000..28087a395b
--- /dev/null
+++ b/runtime/interpreter/safe_math_test.cc
@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "safe_math.h"
+
+#include <limits>
+
+#include "gtest/gtest.h"
+
+namespace art {
+namespace interpreter {
+
+TEST(SafeMath, Add) {
+  // Adding 1 overflows 0x7ff... to 0x800... aka max and min.
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int32_t>::max(), 1),
+            std::numeric_limits<int32_t>::min());
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int64_t>::max(), 1),
+            std::numeric_limits<int64_t>::min());
+
+  // Vanilla arithmetic should work too.
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int32_t>::max() - 1, 1),
+            std::numeric_limits<int32_t>::max());
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int64_t>::max() - 1, 1),
+            std::numeric_limits<int64_t>::max());
+
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int32_t>::min() + 1, -1),
+            std::numeric_limits<int32_t>::min());
+  EXPECT_EQ(SafeAdd(std::numeric_limits<int64_t>::min() + 1, -1),
+            std::numeric_limits<int64_t>::min());
+
+  EXPECT_EQ(SafeAdd(int32_t(-1), -1), -2);
+  EXPECT_EQ(SafeAdd(int64_t(-1), -1), -2);
+
+  EXPECT_EQ(SafeAdd(int32_t(1), 1), 2);
+  EXPECT_EQ(SafeAdd(int64_t(1), 1), 2);
+
+  EXPECT_EQ(SafeAdd(int32_t(-1), 1), 0);
+  EXPECT_EQ(SafeAdd(int64_t(-1), 1), 0);
+
+  EXPECT_EQ(SafeAdd(int32_t(1), -1), 0);
+  EXPECT_EQ(SafeAdd(int64_t(1), -1), 0);
+
+  // Test sign extension of smaller operand sizes.
+  EXPECT_EQ(SafeAdd(int32_t(1), int8_t(-1)), 0);
+  EXPECT_EQ(SafeAdd(int64_t(1), int8_t(-1)), 0);
+}
+
+TEST(SafeMath, Sub) {
+  // Subtracting 1 underflows 0x800... to 0x7ff... aka min and max.
+  EXPECT_EQ(SafeSub(std::numeric_limits<int32_t>::min(), 1),
+            std::numeric_limits<int32_t>::max());
+  EXPECT_EQ(SafeSub(std::numeric_limits<int64_t>::min(), 1),
+            std::numeric_limits<int64_t>::max());
+
+  // Vanilla arithmetic should work too.
+  EXPECT_EQ(SafeSub(std::numeric_limits<int32_t>::max() - 1, -1),
+            std::numeric_limits<int32_t>::max());
+  EXPECT_EQ(SafeSub(std::numeric_limits<int64_t>::max() - 1, -1),
+            std::numeric_limits<int64_t>::max());
+
+  EXPECT_EQ(SafeSub(std::numeric_limits<int32_t>::min() + 1, 1),
+            std::numeric_limits<int32_t>::min());
+  EXPECT_EQ(SafeSub(std::numeric_limits<int64_t>::min() + 1, 1),
+            std::numeric_limits<int64_t>::min());
+
+  EXPECT_EQ(SafeSub(int32_t(-1), -1), 0);
+  EXPECT_EQ(SafeSub(int64_t(-1), -1), 0);
+
+  EXPECT_EQ(SafeSub(int32_t(1), 1), 0);
+  EXPECT_EQ(SafeSub(int64_t(1), 1), 0);
+
+  EXPECT_EQ(SafeSub(int32_t(-1), 1), -2);
+  EXPECT_EQ(SafeSub(int64_t(-1), 1), -2);
+
+  EXPECT_EQ(SafeSub(int32_t(1), -1), 2);
+  EXPECT_EQ(SafeSub(int64_t(1), -1), 2);
+
+  // Test sign extension of smaller operand sizes.
+  EXPECT_EQ(SafeAdd(int32_t(1), int8_t(-1)), 0);
+  EXPECT_EQ(SafeAdd(int64_t(1), int8_t(-1)), 0);
+}
+
+TEST(SafeMath, Mul) {
+  // Multiplying by 2 overflows 0x7ff...f to 0xfff...e aka max and -2.
+  EXPECT_EQ(SafeMul(std::numeric_limits<int32_t>::max(), 2),
+            -2);
+  EXPECT_EQ(SafeMul(std::numeric_limits<int64_t>::max(), 2),
+            -2);
+
+  // Vanilla arithmetic should work too.
+  EXPECT_EQ(SafeMul(std::numeric_limits<int32_t>::max() / 2, 2),
+            std::numeric_limits<int32_t>::max() - 1);  // -1 as LSB is lost by division.
+  EXPECT_EQ(SafeMul(std::numeric_limits<int64_t>::max() / 2, 2),
+            std::numeric_limits<int64_t>::max() - 1);  // -1 as LSB is lost by division.
+
+  EXPECT_EQ(SafeMul(std::numeric_limits<int32_t>::min() / 2, 2),
+            std::numeric_limits<int32_t>::min());
+  EXPECT_EQ(SafeMul(std::numeric_limits<int64_t>::min() / 2, 2),
+            std::numeric_limits<int64_t>::min());
+
+  EXPECT_EQ(SafeMul(int32_t(-1), -1), 1);
+  EXPECT_EQ(SafeMul(int64_t(-1), -1), 1);
+
+  EXPECT_EQ(SafeMul(int32_t(1), 1), 1);
+  EXPECT_EQ(SafeMul(int64_t(1), 1), 1);
+
+  EXPECT_EQ(SafeMul(int32_t(-1), 1), -1);
+  EXPECT_EQ(SafeMul(int64_t(-1), 1), -1);
+
+  EXPECT_EQ(SafeMul(int32_t(1), -1), -1);
+  EXPECT_EQ(SafeMul(int64_t(1), -1), -1);
+
+  // Test sign extension of smaller operand sizes.
+  EXPECT_EQ(SafeMul(int32_t(1), int8_t(-1)), -1);
+  EXPECT_EQ(SafeMul(int64_t(1), int8_t(-1)), -1);
+}
+
+}  // namespace interpreter
+}  // namespace art