Utility functions for checked arithmetic

Provide checkedAdd and checkedMul functions, providing checked
arithmetic on signed integers.

Differential Revision: https://reviews.llvm.org/D43704

llvm-svn: 326516

2 files changed, 72 insertions, 0 deletions

diff --git a/llvm/unittests/Support/CMakeLists.txt b/llvm/unittests/Support/CMakeLists.txt
index 1eb3a04d91d..89e16ef4b3f 100644
--- a/llvm/unittests/Support/CMakeLists.txt
+++ b/llvm/unittests/Support/CMakeLists.txt
@@ -13,6 +13,7 @@ add_llvm_unittest(SupportTests
   CachePruningTest.cpp
   CrashRecoveryTest.cpp
   Casting.cpp
+  CheckedArithmeticTest.cpp
   Chrono.cpp
   CommandLineTest.cpp
   CompressionTest.cpp
diff --git a/llvm/unittests/Support/CheckedArithmeticTest.cpp b/llvm/unittests/Support/CheckedArithmeticTest.cpp
new file mode 100644
index 00000000000..7fc63498e2b
--- /dev/null
+++ b/llvm/unittests/Support/CheckedArithmeticTest.cpp
@@ -0,0 +1,71 @@
+#include "llvm/Support/CheckedArithmetic.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+TEST(CheckedArithmetic, CheckedAdd) {
+  int64_t Out;
+  const int64_t Max = std::numeric_limits<int64_t>::max();
+  const int64_t Min = std::numeric_limits<int64_t>::min();
+  EXPECT_EQ(checkedAdd<int64_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedAdd<int64_t>(Min, -1, &Out), true);
+  EXPECT_EQ(checkedAdd<int64_t>(Max, 1, &Out), true);
+  EXPECT_EQ(checkedAdd<int64_t>(10, 1, &Out), false);
+  EXPECT_EQ(Out, 11);
+}
+
+TEST(CheckedArithmetic, CheckedAddSmall) {
+  int16_t Out;
+  const int16_t Max = std::numeric_limits<int16_t>::max();
+  const int16_t Min = std::numeric_limits<int16_t>::min();
+  EXPECT_EQ(checkedAdd<int16_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedAdd<int16_t>(Min, -1, &Out), true);
+  EXPECT_EQ(checkedAdd<int16_t>(Max, 1, &Out), true);
+  EXPECT_EQ(checkedAdd<int16_t>(10, 1, &Out), false);
+  EXPECT_EQ(Out, 11);
+}
+
+TEST(CheckedArithmetic, CheckedMul) {
+  int64_t Out;
+  const int64_t Max = std::numeric_limits<int64_t>::max();
+  const int64_t Min = std::numeric_limits<int64_t>::min();
+  EXPECT_EQ(checkedMul<int64_t>(Max, 2, &Out), true);
+  EXPECT_EQ(checkedMul<int64_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedMul<int64_t>(Min, 2, &Out), true);
+  EXPECT_EQ(checkedMul<int64_t>(10, 2, &Out), false);
+  EXPECT_EQ(Out, 20);
+}
+
+TEST(CheckedArithmetic, CheckedMulSmall) {
+  int16_t Out;
+  const int16_t Max = std::numeric_limits<int16_t>::max();
+  const int16_t Min = std::numeric_limits<int16_t>::min();
+  EXPECT_EQ(checkedMul<int16_t>(Max, 2, &Out), true);
+  EXPECT_EQ(checkedMul<int16_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedMul<int16_t>(Min, 2, &Out), true);
+  EXPECT_EQ(checkedMul<int16_t>(10, 2, &Out), false);
+  EXPECT_EQ(Out, 20);
+}
+
+TEST(CheckedArithmetic, CheckedAddUnsigned) {
+  uint64_t Out;
+  const uint64_t Max = std::numeric_limits<uint64_t>::max();
+  EXPECT_EQ(checkedAddUnsigned<uint64_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedAddUnsigned<uint64_t>(Max, 1, &Out), true);
+  EXPECT_EQ(checkedAddUnsigned<uint64_t>(10, 1, &Out), false);
+  EXPECT_EQ(Out, uint64_t(11));
+}
+
+TEST(CheckedArithmetic, CheckedMulUnsigned) {
+  uint64_t Out;
+  const uint64_t Max = std::numeric_limits<uint64_t>::max();
+  EXPECT_EQ(checkedMulUnsigned<uint64_t>(Max, 2, &Out), true);
+  EXPECT_EQ(checkedMulUnsigned<uint64_t>(Max, Max, &Out), true);
+  EXPECT_EQ(checkedMulUnsigned<uint64_t>(10, 2, &Out), false);
+  EXPECT_EQ(Out, uint64_t(20));
+}
+
+
+} // namespace