The thing that does
CodeGeneration.
Referred to from several places, the "Code Generator" is a piece of software which, when given appropriate inputs, generates code (Duh!) that can then be compiled. ... Though, technically, a compiler is a
CodeGenerator, too.
Alternatively, it's the software that takes an internal representation of source code and generates
AssemblyLanguage or
MachineCode.
These pages might be of interest: