Control flow graphs to mermaid

Author: kddnewton

.rubocop.yml

@@ -90,6 +90,9 @@ Style/CaseLikeIf:
 Style/ClassVars:
   Enabled: false
 
+Style/CombinableLoops:
+  Enabled: false
+
 Style/DocumentDynamicEvalDefinition:
   Enabled: false
 

lib/syntax_tree/node.rb

@@ -134,12 +134,12 @@ def to_json(*opts)
       accept(Visitor::JSONVisitor.new).to_json(*opts)
     end
 
-    def construct_keys
-      PrettierPrint.format(+"") { |q| accept(Visitor::MatchVisitor.new(q)) }
+    def to_mermaid
+      accept(Visitor::MermaidVisitor.new)
     end
 
-    def mermaid
-      accept(Visitor::MermaidVisitor.new)
+    def construct_keys
+      PrettierPrint.format(+"") { |q| accept(Visitor::MatchVisitor.new(q)) }
     end
   end
 

lib/syntax_tree/yarv/control_flow_graph.rb

@@ -55,6 +55,40 @@ def disasm
         fmt.string
       end
 
+      def to_mermaid
+        output = StringIO.new
+        output.puts("flowchart TD")
+
+        fmt = Disassembler::Mermaid.new
+        blocks.each do |block|
+          output.puts("  subgraph #{block.id}")
+          previous = nil
+
+          block.each_with_length do |insn, length|
+            node_id = "node_#{length}"
+            label = "%04d %s" % [length, insn.disasm(fmt)]
+
+            output.puts("    #{node_id}(\"#{CGI.escapeHTML(label)}\")")
+            output.puts("    #{previous} --> #{node_id}") if previous
+
+            previous = node_id
+          end
+
+          output.puts("  end")
+        end
+
+        blocks.each do |block|
+          block.outgoing_blocks.each do |outgoing|
+            offset =
+              block.block_start + block.insns.sum(&:length) -
+                block.insns.last.length
+            output.puts("  node_#{offset} --> node_#{outgoing.block_start}")
+          end
+        end
+
+        output.string
+      end
+
       # This method is used to verify that the control flow graph is well
       # formed. It does this by checking that each basic block is itself well
       # formed.

lib/syntax_tree/yarv/disassembler.rb

@@ -3,6 +3,41 @@
 module SyntaxTree
   module YARV
     class Disassembler
+      # This class is another object that handles disassembling a YARV
+      # instruction sequence but it does so in order to provide a label for a
+      # mermaid diagram.
+      class Mermaid
+        def calldata(value)
+          value.inspect
+        end
+
+        def enqueue(iseq)
+        end
+
+        def event(name)
+        end
+
+        def inline_storage(cache)
+          "<is:#{cache}>"
+        end
+
+        def instruction(name, operands = [])
+          operands.empty? ? name : "#{name} #{operands.join(", ")}"
+        end
+
+        def label(value)
+          "%04d" % value.name["label_".length..]
+        end
+
+        def local(index, **)
+          index.inspect
+        end
+
+        def object(value)
+          value.inspect
+        end
+      end
+
       attr_reader :output, :queue
 
       attr_reader :current_prefix