Package org.jruby.ir.representations

Class CFGLinearizer

java.lang.Object
org.jruby.ir.representations.CFGLinearizer
public class CFGLinearizer extends Object
This produces a linear list of BasicBlocks so that the linearized instruction list is in executable form. In generating this list, we will also add jumps where required and remove as many jumps as possible.

Ordinary BasicBlocks will follow FollowThrough edges and just concatenate together eliminating the need for executing a jump instruction during execution.

Notes: 1. Basic blocks ending in branches have two edges (FollowTrough/NotTaken and Taken) 2. All BasicBlocks can possibly have two additional edges related to exceptions: - one that transfers control to a rescue block (if one exists that protects the excepting instruction) which is also responsible for running ensures - one that transfers control to an ensure block (if one exists) for situations where we bypass the rescue block (breaks and thread-kill). 3. Branch, Jump, Return, and Exceptions are all boundaries for BasicBlocks 4. Dummy Entry and Exit BasicBlocks exist in all CFGs

NOTE: When the IR builder first builds its list, and the CFG builder builds the CFG, the order in which BBs are created should already be a linearized list. Need to verify this, and we might be able to skip linearization if the CFG has not been transformed by any code transformation passes. This might be the case when JRuby first starts up when we may just build the IR and start interpreting it right away without running any opts. In that scenario, it may be worth it to not run the linearizer at all.

  • Constructor Details

    • CFGLinearizer

      public CFGLinearizer()

  • Method Details