Add math routines with defined wrapping behavior for the interpreter.
Add a RSUB_INT_LIT16 instruction alias to make instruction opcode switch
statements easier to read.
Change-Id: I3bac07c9518665abf0b05b5c3105a90be22f780a
diff --git a/runtime/interpreter/safe_math.h b/runtime/interpreter/safe_math.h
new file mode 100644
index 0000000..78b3539
--- /dev/null
+++ b/runtime/interpreter/safe_math.h
@@ -0,0 +1,65 @@
+/*
+ * 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.
+ */
+
+#ifndef ART_RUNTIME_INTERPRETER_SAFE_MATH_H_
+#define ART_RUNTIME_INTERPRETER_SAFE_MATH_H_
+
+#include <functional>
+#include <type_traits>
+
+namespace art {
+namespace interpreter {
+
+// Declares a type which is the larger in bit size of the two template parameters.
+template <typename T1, typename T2>
+struct select_bigger {
+ typedef typename std::conditional<sizeof(T1) >= sizeof(T2), T1, T2>::type type;
+};
+
+// Perform signed arithmetic Op on 'a' and 'b' with defined wrapping behavior.
+template<template <typename OpT> class Op, typename T1, typename T2>
+static inline typename select_bigger<T1, T2>::type SafeMath(T1 a, T2 b) {
+ typedef typename select_bigger<T1, T2>::type biggest_T;
+ typedef typename std::make_unsigned<biggest_T>::type unsigned_biggest_T;
+ static_assert(std::is_signed<T1>::value, "Expected T1 to be signed");
+ static_assert(std::is_signed<T2>::value, "Expected T2 to be signed");
+ unsigned_biggest_T val1 = static_cast<unsigned_biggest_T>(static_cast<biggest_T>(a));
+ unsigned_biggest_T val2 = static_cast<unsigned_biggest_T>(b);
+ return static_cast<biggest_T>(Op<unsigned_biggest_T>()(val1, val2));
+}
+
+// Perform signed a signed add on 'a' and 'b' with defined wrapping behavior.
+template<typename T1, typename T2>
+static inline typename select_bigger<T1, T2>::type SafeAdd(T1 a, T2 b) {
+ return SafeMath<std::plus>(a, b);
+}
+
+// Perform signed a signed substract on 'a' and 'b' with defined wrapping behavior.
+template<typename T1, typename T2>
+static inline typename select_bigger<T1, T2>::type SafeSub(T1 a, T2 b) {
+ return SafeMath<std::minus>(a, b);
+}
+
+// Perform signed a signed multiply on 'a' and 'b' with defined wrapping behavior.
+template<typename T1, typename T2>
+static inline typename select_bigger<T1, T2>::type SafeMul(T1 a, T2 b) {
+ return SafeMath<std::multiplies>(a, b);
+}
+
+} // namespace interpreter
+} // namespace art
+
+#endif // ART_RUNTIME_INTERPRETER_SAFE_MATH_H_