Structure-Preserving Compilation: Efficient Integration of Functional DSLs into Legacy Systems

We present a translation scheme from a pure functional domain-specific language (DSL) to C. The over-arching idea of this scheme is to preserve the structure of the input pro-gram as much as possible. This includes, among other things, to refrain from inlining user-written functions and to retain variable names as much as possible. We apply this transla-tion scheme to GDSL, a DSL used for the specification of decoders for machine instructions. GDSL offers non-trivial language features such as monadic actions that our transla-tion scheme maps one-to-one to C statements, resulting in code that closely resembles hand-written C code. Indeed, it is feasible to debug and profile the program at the C level and to interface the generated code with existing C code without marshaling data. Our translation scheme is therefore an attractive starting point for a light-weight DSL since no other language-specific tools besides the compiler are necessary. Moreover, the generated code is amenable to compiler optimizations found in off-the-shelf C compilers. This is illustrated by the performance achieved by a decoder for x86 machine instructions implemented in GDSL which is as fast as a production-quality decoding library shipped by Intel