// So far this has only been shown profitable for PGO-hot loop headers.
			// The Hotness values allows distinctions betwen initial blocks that are "hot" or not, and "flow-in" or not.
			// Currently only the initial blocks of loops are tagged in this way;
			// there are no blocks tagged "pgo-hot" that are not also tagged "initial".
			// TODO more heuristics, more architectures.