Fix constant propagation and propagate params in Local2SSA.

Gemfile

@@ -5,4 +5,4 @@ gemspec
 gem "pry"
 gem "ruby-prof", :platforms => :mri
 
-gem "furnace", :github => 'whitequark/furnace'
+gem "furnace", :github => 'whitequark/furnace', :branch => 'master'

lib/furnace-avm2/source/decompiler.rb

@@ -465,7 +465,8 @@ def local_token(node)
         end
       end
     end
-    alias :expr_this :local_token
+    alias :expr_this  :local_token
+    alias :expr_param :local_token
 
     def expr_get(node)
       index, = node.children

lib/furnace-avm2/transform/convert_locals_to_ssa.rb

@@ -30,19 +30,32 @@ def on_get_local(node)
         end
       end
 
+      def initialize(options={})
+        @method = options[:method]
+      end
+
       def transform(cfg)
         next_id      = 0
         variable_map = Hash.new { |h, k| h[k] = Set[] }
 
-        # Prepend implicit `this'.
-        this_set = AST::Node.new(:set_local, [
-            0, AST::Node.new(:this)
-          ], {
-            read_barrier:  Set[],
-            write_barrier: Set[],
-          })
+        # Prepend implicit `this' and params.
+        implicit = 0.upto(1 + @method.param_count).map do |local|
+          case local
+          when 0
+            inner_node = AST::Node.new(:this)
+          else
+            inner_node = AST::Node.new(:param, [ local - 1 ])
+          end
+
+          AST::Node.new(:set_local, [
+              local, inner_node
+            ], {
+              read_barrier:  Set[],
+              write_barrier: Set[],
+            })
+        end
 
-        cfg.entry.insns.insert(0, this_set)
+        cfg.entry.insns.insert(0, *implicit)
 
         # Convert (set-local) to (s).
         cfg.nodes.each do |block|

lib/furnace-avm2/transform/propagate_constants.rb

@@ -16,14 +16,15 @@ def transform(cfg)
             # TODO add options for folding complex constants
             if evaluator.immediate?(set_value) ||
                 set_value.type == :this ||
+                set_value.type == :param ||
                 set_value.type == :find_property_strict
 
-              replace_r_nodes(cfg, block, id, set_value) do |child_block|
-                child_block.metadata.live.delete id
-              end
+              replaced_all = replace_r_nodes(cfg, block, id, set_value)
 
-              block.metadata.remove_set id
-              block.insns.delete set
+              if replaced_all
+                block.metadata.remove_set id
+                block.insns.delete set
+              end
 
               changed = true
             end

lib/furnace-avm2/transform/subgraph_operations.rb

@@ -85,18 +85,30 @@ def reduce_phi_nodes(cfg, root, target_id, supplementary_id)
       end
 
       def replace_r_nodes(cfg, root, target_id, replacement)
+        replaced_all = true
+
         walk_live_nodes(cfg, root, target_id) do |block|
           gets = block.metadata.gets_map[target_id]
           gets.each do |get|
-            get.update(replacement.type,
-                replacement.children,
-                replacement.metadata)
+            if get.children.one?
+              get.update(replacement.type,
+                  replacement.children,
+                  replacement.metadata)
+            else
+              replaced_all = false
+            end
           end
 
           block.metadata.unregister_get target_id
+        end
 
-          yield block if block_given?
+        if replaced_all
+          walk_live_nodes(cfg, root, target_id) do |block|
+            block.metadata.live.delete target_id
+          end
         end
+
+        replaced_all
       end
     end
   end