From 7bee31689049dd825ff390fa30fe3645f2d87877 Mon Sep 17 00:00:00 2001
From: Nathan Slingerland <slingn@gmail.com>
Date: Tue, 12 Jan 2016 22:34:00 +0000
Subject: [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
---
 llvm/unittests/Support/MathExtrasTest.cpp | 54 +++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

(limited to 'llvm/unittests/Support/MathExtrasTest.cpp')

diff --git a/llvm/unittests/Support/MathExtrasTest.cpp b/llvm/unittests/Support/MathExtrasTest.cpp
index 945d8322b25..97309f8d31f 100644
--- a/llvm/unittests/Support/MathExtrasTest.cpp
+++ b/llvm/unittests/Support/MathExtrasTest.cpp
@@ -304,4 +304,58 @@ TEST(MathExtras, SaturatingMultiply) {
   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>();
+}
+
 }
-- 
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