2 files changed, 62 insertions, 5 deletions
diff --git a/include/llvm/Analysis/BlockFrequencyInfoImpl.h b/include/llvm/Analysis/BlockFrequencyInfoImpl.h
index bd72d3ed6d..7ad76e5350 100644
--- a/include/llvm/Analysis/BlockFrequencyInfoImpl.h
+++ b/include/llvm/Analysis/BlockFrequencyInfoImpl.h
@@ -22,6 +22,7 @@
 #include "llvm/Support/BlockFrequency.h"
 #include "llvm/Support/BranchProbability.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/ScaledNumber.h"
 #include "llvm/Support/raw_ostream.h"
 #include <deque>
 #include <list>
@@ -343,12 +344,11 @@ private:
   }
 
   static UnsignedFloat getRounded(UnsignedFloat P, bool Round) {
-    if (!Round)
+    // Saturate.
+    if (P.isLargest())
       return P;
-    if (P.Digits == DigitsLimits::max())
-      // Careful of overflow in the exponent.
-      return UnsignedFloat(1, P.Exponent) <<= Width;
-    return UnsignedFloat(P.Digits + 1, P.Exponent);
+
+    return ScaledNumbers::getRounded(P.Digits, P.Exponent, Round);
   }
 };
 
diff --git a/include/llvm/Support/ScaledNumber.h b/include/llvm/Support/ScaledNumber.h
new file mode 100644
index 0000000000..afdc7dc188
--- /dev/null
+++ b/include/llvm/Support/ScaledNumber.h
@@ -0,0 +1,57 @@
+//===- llvm/Support/ScaledNumber.h - Support for scaled numbers -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains functions (and a class) useful for working with scaled
+// numbers -- in particular, pairs of integers where one represents digits and
+// another represents a scale.  The functions are helpers and live in the
+// namespace ScaledNumbers.  The class ScaledNumber is useful for modelling
+// certain cost metrics that need simple, integer-like semantics that are easy
+// to reason about.
+//
+// These might remind you of soft-floats.  If you want one of those, you're in
+// the wrong place.  Look at include/llvm/ADT/APFloat.h instead.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_SCALEDNUMBER_H
+#define LLVM_SUPPORT_SCALEDNUMBER_H
+
+#include <cstdint>
+#include <limits>
+#include <utility>
+
+namespace llvm {
+namespace ScaledNumbers {
+
+/// \brief Get the width of a number.
+template <class DigitsT> inline int getWidth() { return sizeof(DigitsT) * 8; }
+
+/// \brief Conditionally round up a scaled number.
+///
+/// Given \c Digits and \c Scale, round up iff \c ShouldRound is \c true.
+/// Always returns \c Scale unless there's an overflow, in which case it
+/// returns \c 1+Scale.
+///
+/// \pre adding 1 to \c Scale will not overflow INT16_MAX.
+template <class DigitsT>
+inline std::pair<DigitsT, int16_t> getRounded(DigitsT Digits, int16_t Scale,
+                                              bool ShouldRound) {
+  static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
+
+  if (ShouldRound)
+    if (!++Digits)
+      // Overflow.
+      return std::make_pair(DigitsT(1) << (getWidth<DigitsT>() - 1), Scale + 1);
+  return std::make_pair(Digits, Scale);
+}
+}
+}
+
+#endif
+