The Compilation Manager (CM) is SML/NJ’s mechanism for supporting programming-in-the-very-large.
Porting SML/NJ CM files to MLton
To help in porting CM files to MLton, the MLton source distribution
includes the sources for a utility, cm2mlb, that will print an
ML Basis file with essentially the same semantics as the
CM file — handling the full syntax of CM supported by your installed
SML/NJ version and correctly handling export filters.  When cm2mlb
encounters a .cm import, it attempts to convert it to a
corresponding .mlb import.  CM anchored paths are translated to
paths according to a default configuration file
(cm2mlb-map). For example,
the default configuration includes
# Standard ML Basis Library $SMLNJ-BASIS $(SML_LIB)/basis $basis.cm $(SML_LIB)/basis $basis.cm/basis.cm $(SML_LIB)/basis/basis.mlb
to ensure that a $/basis.cm import is translated to a
$(SML_LIB)/basis/basis.mlb import.  See util/cm2mlb for details.
Building cm2mlb requires that you have already installed a recent
version of SML/NJ.