Avail
AvailInstruction implements an abstract instruction set that doesn't have to agree precisely with the actual implemented Level One nybblecode instruction set. The mapping is approximately one-to-one, however, other than providing the ability to defer certain analyses, such as last-use of variables, until after selection of AvailInstructions. This allows the analysis to simply mark the already abstractly-emitted instructions with information that affects the precise nybblecodes that will ultimately be emitted.
Author
Mark van Gulik
Parameters
Inheritors
Constructors
Properties
true iff this instruction is a use of an outer variable.
Answer which line number to say that this instruction occurs on. Use the relevantTokens as an approximation, but subclasses might be able to be more precise. Answer -1 if this instruction doesn't seem to have a location in the source associated with it.
The tuple of tokens that contributed to producing this instruction.
Functions
The instructions of a block are being iterated over. Coordinate optimizations between instructions using localData and outerData, two lists manipulated by overrides of this method. Treat each instruction as though it is the last one in the block, and save enough information in the lists to be able to undo consequences of this assumption when a later instruction shows it to be unwarranted.
Write an entry to the encoded line number deltas for each L1 instruction generated. Most AvailInstructions write a single L1 instruction, so that implementation is here.
Write nybbles representing this instruction to the NybbleOutputStream.