\section{Regmap} A \newdef{regmap} is a mapping from virtual register to virtual or physical register, and is used by MLRISC register allocators to represent the current binding of virtual registers. Regmaps are implemented as \mlrischref{library/intmap.sml}{Intmap} in MLRISC, and are defined in the \href{cells.html}{CELLS} interface. Regmaps are used in phases such as \href{asm.html}{assembly generation} and \href{mc.html}{machine code}. MLRISC program representations such \href{cluster.html}{clusters} and \href{mlrisc-ir.html}{IR} each contains a global regmap per compilation unit. Representations such as \href{hyperblock.html}{hyperblock} may contain its own regmap, which overrides the global regmap.