Add a division operator to BlockFrequency.

Allow a BlockFrequency to be divided by a non-zero BranchProbability
with saturating arithmetic. This will be used to compute the frequency
of a loop header given the probability of leaving the loop.

Our long division algorithm already saturates on overflow, so that was a
freebie.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185184 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 0 deletions

diff --git a/include/llvm/Support/BlockFrequency.h b/include/llvm/Support/BlockFrequency.h
index 85e9437a57..147d52abe4 100644
--- a/include/llvm/Support/BlockFrequency.h
+++ b/include/llvm/Support/BlockFrequency.h
@@ -27,6 +27,9 @@ class BlockFrequency {
   uint64_t Frequency;
   static const int64_t ENTRY_FREQ = 1 << 14;
 
+  // Scale frequency by N/D, saturating on overflow.
+  void scale(uint32_t N, uint32_t D);
+
 public:
   BlockFrequency(uint64_t Freq = 0) : Frequency(Freq) { }
 
@@ -42,6 +45,11 @@ public:
   BlockFrequency &operator*=(const BranchProbability &Prob);
   const BlockFrequency operator*(const BranchProbability &Prob) const;
 
+  /// \brief Divide by a non-zero branch probability using saturating
+  /// arithmetic.
+  BlockFrequency &operator/=(const BranchProbability &Prob);
+  BlockFrequency operator/(const BranchProbability &Prob) const;
+
   /// \brief Adds another block frequency using saturating arithmetic.
   BlockFrequency &operator+=(const BlockFrequency &Freq);
   const BlockFrequency operator+(const BlockFrequency &Freq) const;