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5.3.8 lookup Instruction

The instruction is the mixed type one, which can be generated when disassembling a node of a multinode model that has positive length of the look-ahead signal segment. That length is specified when creating the multinode model and can be retrieved using the function qsmm_get_ngram_env_la_sz.

The instruction has syntax

        lookup  position

The instruction sets the outcome to a look-ahead signal at given zero-based position.

When the length of the look-ahead signal segment of a multinode model is positive, assembler programs cannot be loaded into nodes of the multinode model. Therefore, if you need to assemble a program that contains lookup instructions (e.g. generated by the disassembler), you have to create a model with the zero-length look-ahead signal segment. You have to define instruction meta-class ‘lookup’ that fetches signals at given positions from an array used as a substitute for the look-ahead signal segment. You also need to register necessary instruction classes derived from instruction meta-class ‘lookup’, the number of which is equal to the number of possible values of position.