1 files changed, 45 insertions, 4 deletions
diff --git a/lib/Support/BranchProbability.cpp b/lib/Support/BranchProbability.cpp
index 65878d6e3025..771d02c0aa3c 100644
--- a/lib/Support/BranchProbability.cpp
+++ b/lib/Support/BranchProbability.cpp
@@ -15,17 +15,58 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cassert>
 
 using namespace llvm;
 
+const uint32_t BranchProbability::D;
+
 raw_ostream &BranchProbability::print(raw_ostream &OS) const {
-  return OS << N << " / " << D << " = "
-            << format("%g%%", ((double)N / D) * 100.0);
+  if (isUnknown())
+    return OS << "?%";
+
+  // Get a percentage rounded to two decimal digits. This avoids
+  // implementation-defined rounding inside printf.
+  double Percent = rint(((double)N / D) * 100.0 * 100.0) / 100.0;
+  return OS << format("0x%08" PRIx32 " / 0x%08" PRIx32 " = %.2f%%", N, D,
+                      Percent);
 }
 
 void BranchProbability::dump() const { print(dbgs()) << '\n'; }
 
+BranchProbability::BranchProbability(uint32_t Numerator, uint32_t Denominator) {
+  assert(Denominator > 0 && "Denominator cannot be 0!");
+  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
+  if (Denominator == D)
+    N = Numerator;
+  else {
+    uint64_t Prob64 =
+        (Numerator * static_cast<uint64_t>(D) + Denominator / 2) / Denominator;
+    N = static_cast<uint32_t>(Prob64);
+  }
+}
+
+BranchProbability
+BranchProbability::getBranchProbability(uint64_t Numerator,
+                                        uint64_t Denominator) {
+  assert(Numerator <= Denominator && "Probability cannot be bigger than 1!");
+  // Scale down Denominator to fit in a 32-bit integer.
+  int Scale = 0;
+  while (Denominator > UINT32_MAX) {
+    Denominator >>= 1;
+    Scale++;
+  }
+  return BranchProbability(Numerator >> Scale, Denominator);
+}
+
+// If ConstD is not zero, then replace D by ConstD so that division and modulo
+// operations by D can be optimized, in case this function is not inlined by the
+// compiler.
+template <uint32_t ConstD>
 static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
+  if (ConstD > 0)
+    D = ConstD;
+
   assert(D && "divide by 0");
 
   // Fast path for multiplying by 1.0.
@@ -65,9 +106,9 @@ static uint64_t scale(uint64_t Num, uint32_t N, uint32_t D) {
 }
 
 uint64_t BranchProbability::scale(uint64_t Num) const {
-  return ::scale(Num, N, D);
+  return ::scale<D>(Num, N, D);
 }
 
 uint64_t BranchProbability::scaleByInverse(uint64_t Num) const {
-  return ::scale(Num, D, N);
+  return ::scale<0>(Num, D, N);
 }