[llvm] r253412 - [llvm-profdata] Add SaturatingAdd/SaturatingMultiply Helper Functions
Nathan Slingerland via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 17 16:52:43 PST 2015
Author: slingn
Date: Tue Nov 17 18:52:43 2015
New Revision: 253412
URL: http://llvm.org/viewvc/llvm-project?rev=253412&view=rev
Log:
[llvm-profdata] Add SaturatingAdd/SaturatingMultiply Helper Functions
Summary:
This change adds MathExtras helper functions for handling unsigned, saturating addition and multiplication. It also updates the instrumentation and sample profile merge implementations to use them.
No functional changes.
Reviewers: dnovillo, bogner, davidxl
Subscribers: davidxl, llvm-commits
Differential Revision: http://reviews.llvm.org/D14720
Modified:
llvm/trunk/include/llvm/ProfileData/InstrProf.h
llvm/trunk/include/llvm/ProfileData/SampleProf.h
llvm/trunk/include/llvm/Support/MathExtras.h
llvm/trunk/unittests/Support/MathExtrasTest.cpp
Modified: llvm/trunk/include/llvm/ProfileData/InstrProf.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ProfileData/InstrProf.h?rev=253412&r1=253411&r2=253412&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ProfileData/InstrProf.h (original)
+++ llvm/trunk/include/llvm/ProfileData/InstrProf.h Tue Nov 17 18:52:43 2015
@@ -226,7 +226,7 @@ struct InstrProfValueSiteRecord {
while (I != IE && I->Value < J->Value)
++I;
if (I != IE && I->Value == J->Value) {
- I->Count += J->Count;
+ I->Count = SaturatingAdd(I->Count, J->Count);
++I;
continue;
}
Modified: llvm/trunk/include/llvm/ProfileData/SampleProf.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ProfileData/SampleProf.h?rev=253412&r1=253411&r2=253412&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ProfileData/SampleProf.h (original)
+++ llvm/trunk/include/llvm/ProfileData/SampleProf.h Tue Nov 17 18:52:43 2015
@@ -173,10 +173,7 @@ public:
/// Sample counts accumulate using saturating arithmetic, to avoid wrapping
/// around unsigned integers.
void addSamples(uint64_t S) {
- if (NumSamples <= std::numeric_limits<uint64_t>::max() - S)
- NumSamples += S;
- else
- NumSamples = std::numeric_limits<uint64_t>::max();
+ NumSamples = SaturatingAdd(NumSamples, S);
}
/// Add called function \p F with samples \p S.
@@ -185,10 +182,7 @@ public:
/// around unsigned integers.
void addCalledTarget(StringRef F, uint64_t S) {
uint64_t &TargetSamples = CallTargets[F];
- if (TargetSamples <= std::numeric_limits<uint64_t>::max() - S)
- TargetSamples += S;
- else
- TargetSamples = std::numeric_limits<uint64_t>::max();
+ TargetSamples = SaturatingAdd(TargetSamples, S);
}
/// Return true if this sample record contains function calls.
Modified: llvm/trunk/include/llvm/Support/MathExtras.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/MathExtras.h?rev=253412&r1=253411&r2=253412&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/MathExtras.h (original)
+++ llvm/trunk/include/llvm/Support/MathExtras.h Tue Nov 17 18:52:43 2015
@@ -653,6 +653,32 @@ inline int64_t SignExtend64(uint64_t X,
return int64_t(X << (64 - B)) >> (64 - B);
}
+/// \brief Add two unsigned integers, X and Y, of type T.
+/// Clamp the result to the maximum representable value of T on overflow.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+SaturatingAdd(T X, T Y) {
+ // Hacker's Delight, p. 29
+ T Z = X + Y;
+ if (Z < X || Z < Y)
+ return std::numeric_limits<T>::max();
+ else
+ return Z;
+}
+
+/// \brief Multiply two unsigned integers, X and Y, of type T.
+/// Clamp the result to the maximum representable value of T on overflow.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+SaturatingMultiply(T X, T Y) {
+ // Hacker's Delight, p. 30
+ T Z = X * Y;
+ if (Y != 0 && Z / Y != X)
+ return std::numeric_limits<T>::max();
+ else
+ return Z;
+}
+
extern const float huge_valf;
} // End llvm namespace
Modified: llvm/trunk/unittests/Support/MathExtrasTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/Support/MathExtrasTest.cpp?rev=253412&r1=253411&r2=253412&view=diff
==============================================================================
--- llvm/trunk/unittests/Support/MathExtrasTest.cpp (original)
+++ llvm/trunk/unittests/Support/MathExtrasTest.cpp Tue Nov 17 18:52:43 2015
@@ -190,4 +190,52 @@ TEST(MathExtras, RoundUpToAlignment) {
EXPECT_EQ(552u, RoundUpToAlignment(321, 255, 42));
}
+template<typename T>
+void SaturatingAddTestHelper()
+{
+ EXPECT_EQ(static_cast<T>(3),
+ SaturatingAdd(static_cast<T>(1), static_cast<T>(2)));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingAdd(std::numeric_limits<T>::max(), static_cast<T>(1)));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingAdd(static_cast<T>(1), std::numeric_limits<T>::max()));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingAdd(std::numeric_limits<T>::max(),
+ std::numeric_limits<T>::max()));
+}
+
+TEST(MathExtras, SaturatingAdd) {
+ SaturatingAddTestHelper<uint8_t>();
+ SaturatingAddTestHelper<uint16_t>();
+ SaturatingAddTestHelper<uint32_t>();
+ SaturatingAddTestHelper<uint64_t>();
+}
+
+template<typename T>
+void SaturatingMultiplyTestHelper()
+{
+ EXPECT_EQ(static_cast<T>(0),
+ SaturatingMultiply(static_cast<T>(1), static_cast<T>(0)));
+ EXPECT_EQ(static_cast<T>(0),
+ SaturatingMultiply(static_cast<T>(0), static_cast<T>(1)));
+ EXPECT_EQ(static_cast<T>(6),
+ SaturatingMultiply(static_cast<T>(2), static_cast<T>(3)));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingMultiply(std::numeric_limits<T>::max(),
+ static_cast<T>(2)));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingMultiply(static_cast<T>(2),
+ std::numeric_limits<T>::max()));
+ EXPECT_EQ(std::numeric_limits<T>::max(),
+ SaturatingMultiply(std::numeric_limits<T>::max(),
+ std::numeric_limits<T>::max()));
+}
+
+TEST(MathExtras, SaturatingMultiply) {
+ SaturatingMultiplyTestHelper<uint8_t>();
+ SaturatingMultiplyTestHelper<uint16_t>();
+ SaturatingMultiplyTestHelper<uint32_t>();
+ SaturatingMultiplyTestHelper<uint64_t>();
+}
+
}
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