Module: Laser::Analysis::ControlFlow::ConstantPropagation

Included in:
ControlFlowGraph
Defined in:
lib/laser/analysis/control_flow/constant_propagation.rb

Overview

Sparse Conditional Constant Propagation: Wegman and Zadeck Love those IBMers Using Morgan's implementation though.

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Instance Attribute Details

- (Object) constants (readonly)

Returns the value of attribute constants



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# File 'lib/laser/analysis/control_flow/constant_propagation.rb', line 10

def constants
  @constants
end

Instance Method Details

- (Object) perform_constant_propagation(opts = {})

Only public method: mutably turns the CFG into a constant-propagated one. Each binding will have a value assigned to it afterward: either the constant, as a Ruby object (or a proxy to one), UNDEFINED, or VARYING.



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# File 'lib/laser/analysis/control_flow/constant_propagation.rb', line 15

def perform_constant_propagation(opts={})
  opts = {fixed_methods: {}, initial_block: self.enter}.merge(opts)
  
  initialize_constant_propagation(opts)
  visited = Set.new
  worklist = Set.new
  blocklist = Set[opts[:initial_block]]
  while worklist.any? || blocklist.any?
    while worklist.any?
      constant_propagation_for_instruction(
          worklist.pop, blocklist, worklist, opts)
    end
    while blocklist.any?
      constant_propagation_for_block(
          blocklist.pop, visited, blocklist, worklist, opts)
    end
  end
  teardown_constant_propagation
  @constants = find_remaining_constants
end