[Support] Add saturating multiply-add support function
Summary: Add SaturatingMultiplyAdd convenience function template since A + (X * Y) comes up frequently when doing weighted arithmetic.
Reviewers: davidxl, silvas
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15385
llvm-svn: 257532
diff --git a/llvm/unittests/Support/MathExtrasTest.cpp b/llvm/unittests/Support/MathExtrasTest.cpp
index 945d832..97309f8 100644
--- a/llvm/unittests/Support/MathExtrasTest.cpp
+++ b/llvm/unittests/Support/MathExtrasTest.cpp
@@ -304,4 +304,58 @@
SaturatingMultiplyTestHelper<uint64_t>();
}
+template<typename T>
+void SaturatingMultiplyAddTestHelper()
+{
+ const T Max = std::numeric_limits<T>::max();
+ bool ResultOverflowed;
+
+ // Test basic multiply-add.
+ EXPECT_EQ(T(16), SaturatingMultiplyAdd(T(2), T(3), T(10)));
+ EXPECT_EQ(T(16), SaturatingMultiplyAdd(T(2), T(3), T(10), &ResultOverflowed));
+ EXPECT_FALSE(ResultOverflowed);
+
+ // Test multiply overflows, add doesn't overflow
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(Max, Max, T(0), &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ // Test multiply doesn't overflow, add overflows
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(T(1), T(1), Max, &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ // Test multiply-add with Max as operand
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(T(1), T(1), Max, &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(T(1), Max, T(1), &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(Max, Max, T(1), &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ EXPECT_EQ(Max, SaturatingMultiplyAdd(Max, Max, Max, &ResultOverflowed));
+ EXPECT_TRUE(ResultOverflowed);
+
+ // Test multiply-add with 0 as operand
+ EXPECT_EQ(T(1), SaturatingMultiplyAdd(T(1), T(1), T(0), &ResultOverflowed));
+ EXPECT_FALSE(ResultOverflowed);
+
+ EXPECT_EQ(T(1), SaturatingMultiplyAdd(T(1), T(0), T(1), &ResultOverflowed));
+ EXPECT_FALSE(ResultOverflowed);
+
+ EXPECT_EQ(T(1), SaturatingMultiplyAdd(T(0), T(0), T(1), &ResultOverflowed));
+ EXPECT_FALSE(ResultOverflowed);
+
+ EXPECT_EQ(T(0), SaturatingMultiplyAdd(T(0), T(0), T(0), &ResultOverflowed));
+ EXPECT_FALSE(ResultOverflowed);
+
+}
+
+TEST(MathExtras, SaturatingMultiplyAdd) {
+ SaturatingMultiplyAddTestHelper<uint8_t>();
+ SaturatingMultiplyAddTestHelper<uint16_t>();
+ SaturatingMultiplyAddTestHelper<uint32_t>();
+ SaturatingMultiplyAddTestHelper<uint64_t>();
+}
+
}