1 files changed, 57 insertions, 0 deletions
diff --git a/src/base/types.hh b/src/base/types.hh
index ba6d53ad7..4caf92c97 100644
--- a/src/base/types.hh
+++ b/src/base/types.hh
@@ -39,6 +39,8 @@
 
 #include <inttypes.h>
 
+#include <cassert>
+
 /** uint64_t constant */
 #define ULL(N)          ((uint64_t)N##ULL)
 /** int64_t constant */
@@ -58,6 +60,61 @@ typedef uint64_t Tick;
 const Tick MaxTick = ULL(0xffffffffffffffff);
 
 /**
+ * Cycles is a wrapper class for representing cycle counts, i.e. a
+ * relative difference between two points in time, expressed in a
+ * number of clock cycles.
+ *
+ * The Cycles wrapper class is a type-safe alternative to a
+ * typedef, aiming to avoid unintentional mixing of cycles and ticks
+ * in the code base.
+ *
+ * Operators are defined inside an ifndef block to avoid swig touching
+ * them. Note that there is no overloading of the bool operator as the
+ * compiler is allowed to turn booleans into integers and this causes
+ * a whole range of issues in a handful locations. The solution to
+ * this problem would be to use the safe bool idiom, but for now we
+ * make do without the test and use the more elaborate comparison >
+ * Cycles(0).
+ */
+class Cycles
+{
+
+  private:
+
+    /** Member holding the actual value. */
+    uint64_t c;
+
+  public:
+
+    /** Explicit constructor assigning a value. */
+    explicit Cycles(uint64_t _c) : c(_c) { }
+
+#ifndef SWIG // keep the operators away from SWIG
+
+    /** Converting back to the value type. */
+    operator uint64_t() const { return c; }
+
+    /** Prefix increment operator. */
+    Cycles& operator++()
+    { ++c; return *this; }
+
+    /** Prefix decrement operator. Is only temporarily used in the O3 CPU. */
+    Cycles& operator--()
+    { assert(c != 0); --c; return *this; }
+
+    /** In-place addition of cycles. */
+    const Cycles& operator+=(const Cycles& cc)
+    { c += cc.c; return *this; }
+
+    /** Greater than comparison used for > Cycles(0). */
+    bool operator>(const Cycles& cc) const
+    { return c > cc.c; }
+
+#endif // SWIG not touching operators
+
+};
+
+/**
  * Address type
  * This will probably be moved somewhere else in the near future.
  * This should be at least as big as the biggest address width in use