The E-code dynamic code generator operates by parsing the source language and emitting the appropriate instructions into a memory buffer from which they can be executed directly. Currently, E-code supports dynamic code generation for Intel x86, MIPS, StrongARM, and Sun SPARC (32- and 64-bit) processors. Support for Intel's 64-bit EPIC architecture is under development.
The code generator is subroutine-based and does not require invocation of external binaries. Code is emitted during parsing in the form of virtual instructions for an idealized RISC architecture. Simple, low-hanging fruit optimizations are applied (constant propagation, register renaming, and limited common subexpression elimination), and then the virtual instructions are mapped to their physical counterparts for the target architecture.
E-code's early versions were based upon Icode, an internal interface developed at MIT as part of the 'C project [19]. Icode is itself based on Vcode [11], also developed at MIT by Dawson Engler. E-code's recent versions, however, are based on DRISC, a low-level DCG package developed at Georgia Tech. The performance of the two versions are similar. More information about characteristics of the E-code language, such as examples of the generated code, further details on its performance, and generation times can be found elsewhere [10].