ISDL: an instruction set description language for retargetability

We present the Instruction Set Description Language,ISDL, a machine description language used to describetarget architectures to a retargetable compiler. The featuresand flexibility of ISDL enable the description of vastly differentarchitectures, in particular VLIW architectures. ISDL explicitlysupports constraints that define valid operation groupingswithin an instruction, increasing the range of specifiable architectures.We have written a tool that, given an ISDL descriptionof a processor, automatically generates an assembler forit. Ongoing work includes the development of an automaticcode-generator generator.