[block-freq] Add a right shift to BlockFrequency that saturates at 1.
llvm-svn: 197302
diff --git a/llvm/include/llvm/Support/BlockFrequency.h b/llvm/include/llvm/Support/BlockFrequency.h
index 997d11e..dae520b 100644
--- a/llvm/include/llvm/Support/BlockFrequency.h
+++ b/llvm/include/llvm/Support/BlockFrequency.h
@@ -55,6 +55,9 @@
BlockFrequency &operator+=(const BlockFrequency &Freq);
const BlockFrequency operator+(const BlockFrequency &Freq) const;
+ /// \brief Shift block frequency to the right by count digits saturating to 1.
+ BlockFrequency &operator>>=(const unsigned count);
+
/// \brief Scale the given BlockFrequency by N/D. Return the remainder from
/// the division by D. Upon overflow, the routine will saturate.
uint32_t scale(const BranchProbability &Prob);
diff --git a/llvm/lib/Support/BlockFrequency.cpp b/llvm/lib/Support/BlockFrequency.cpp
index d1f8408..00cf75b 100644
--- a/llvm/lib/Support/BlockFrequency.cpp
+++ b/llvm/lib/Support/BlockFrequency.cpp
@@ -145,6 +145,18 @@
return Freq;
}
+BlockFrequency &BlockFrequency::operator>>=(const unsigned count) {
+ // Frequency can never be 0 by design.
+ assert(Frequency != 0);
+
+ // Shift right by count.
+ Frequency >>= count;
+
+ // Saturate to 1 if we are 0.
+ Frequency |= Frequency == 0;
+ return *this;
+}
+
uint32_t BlockFrequency::scale(const BranchProbability &Prob) {
return scale(Prob.getNumerator(), Prob.getDenominator());
}
diff --git a/llvm/unittests/Support/BlockFrequencyTest.cpp b/llvm/unittests/Support/BlockFrequencyTest.cpp
index ffdea2c..c318451 100644
--- a/llvm/unittests/Support/BlockFrequencyTest.cpp
+++ b/llvm/unittests/Support/BlockFrequencyTest.cpp
@@ -237,4 +237,12 @@
EXPECT_FALSE(BigZero >= BigOne);
}
+TEST(BlockFrequencyTest, SaturatingRightShift) {
+ BlockFrequency Freq(0x10080ULL);
+ Freq >>= 2;
+ EXPECT_EQ(Freq.getFrequency(), 0x4020ULL);
+ Freq >>= 20;
+ EXPECT_EQ(Freq.getFrequency(), 0x1ULL);
+}
+
}