\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. 
