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Contents
module Furnace
module Transform
module Generic
class LabelNormalize
include AST::Visitor
def transform(ast, method)
# Find the minimal label in each operation sub-tree.
# It's the operation entry point.
visit ast
# Traverse operations in reverse order and bypass all jump_target's,
# recording the forwarded address in label_map.
label_map = {}
last_real_operation = nil
ast.children.reverse.each do |child|
if child.type == :jump_target
label = last_real_operation
else
label = child.metadata[:label]
last_real_operation = label
end
label_map[child.metadata[:label]] = label
end
# Remove jump_target's.
ast.children.reject! { |c| c.type == :jump_target }
# Find all jumpable labels and substitute the addresses to forward
# through jump_target's.
target_map = []
ast.children.each do |child|
if child.type == :jump || child.type == :jump_if
forwarded_target = label_map[child.children[0]]
child.children[0] = forwarded_target
target_map << forwarded_target
end
end
[ ast, target_map, method ]
end
def on_any(node)
return if node.type == :root
child_nodes = node.children.select { |c| c.is_a? AST::Node }
new_label = child_nodes.map { |c| c.metadata[:label] }.compact.min
node.metadata[:label] = new_label if new_label
child_nodes.each { |c| c.metadata.delete :label }
end
end
end
end
end
Version data entries
10 entries across 10 versions & 1 rubygems