+/// \brief Unreachable-terminating branch taken weight.
+///
+/// This is the weight for a branch being taken to a block that terminates
+/// (eventually) in unreachable. These are predicted as unlikely as possible.
+static const uint32_t UR_TAKEN_WEIGHT = 1;
+
+/// \brief Unreachable-terminating branch not-taken weight.
+///
+/// This is the weight for a branch not being taken toward a block that
+/// terminates (eventually) in unreachable. Such a branch is essentially never
+/// taken. Set the weight to an absurdly high value so that nested loops don't
+/// easily subsume it.
+static const uint32_t UR_NONTAKEN_WEIGHT = 1024*1024 - 1;
+
+/// \brief Weight for a branch taken going into a cold block.
+///
+/// This is the weight for a branch taken toward a block marked
+/// cold. A block is marked cold if it's postdominated by a
+/// block containing a call to a cold function. Cold functions
+/// are those marked with attribute 'cold'.
+static const uint32_t CC_TAKEN_WEIGHT = 4;
+
+/// \brief Weight for a branch not-taken into a cold block.
+///
+/// This is the weight for a branch not taken toward a block marked
+/// cold.
+static const uint32_t CC_NONTAKEN_WEIGHT = 64;