new register allocation generates good looking push/pop

lib/ast/call_site_expression.rb

@@ -22,12 +22,12 @@ module Ast
       raise "No receiver error #{inspect}:#{value_receiver}:#{name}" if (value_receiver.nil?)
       call = Vm::CallSite.new( name ,  value_receiver , params  , function)
       current_function = context.function
-      current_function.save_locals(context , into) if current_function
+      into.push([])  unless current_function.nil?
       call.load_args into
       call.do_call into
       after = into.new_block("#{into.name}_call#{@@counter+=1}")
       into.insert_at after
-      current_function.restore_locals(context , after) if current_function
+      after.pop([]) unless current_function.nil?
       puts "compile call #{function.return_type}"
       function.return_type
     end

lib/ast/if_expression.rb

@@ -11,7 +11,8 @@ module Ast
       puts "compiling if condition #{cond}"
       cond_val = cond.compile(context , into)
       into.b true_block , condition_code: cond_val.operator
-            
+      into.branch = true_block
+
       if_false.each do |part|
         puts "compiling in if false #{part}"
         last = part.compile(context , false_block )

lib/ast/while_expression.rb

@@ -7,6 +7,8 @@ module Ast
       puts "compiling while condition #{condition}"
       cond_val = condition.compile(context , while_block)
       while_block.b ret , condition_code: cond_val.not_operator
+      while_block.branch = ret
+
       last = nil
       body.each do |part|
         puts "compiling in while #{part}"

lib/vm/block.rb

@@ -25,6 +25,7 @@ module Vm
       @function = function
       @name = name.to_sym
       @next = next_block
+      @branch = nil
       @codes = []
       @insert_at = self
       # keeping track of register usage, left (assigns) or right (uses)
@@ -33,15 +34,27 @@ module Vm
     end
 
     attr_reader :name  , :next , :codes , :function , :assigns , :uses
+    attr_accessor :branch
+    
+    def reachable
+      ret = []
+      add_next ret
+      add_branch ret
+      ret
+    end
 
     def add_code(kode)
       raise "alarm #{kode}" if kode.is_a? Word
       raise "alarm #{kode.class} #{kode}" unless kode.is_a? Code
-      @assigns += kode.assigns
-      @uses += kode.uses
-      @insert_at.codes << kode
+      @insert_at.do_add kode
       self
     end
+    def do_add kode
+      kode.assigns.each { |a| (@assigns << a) unless @assigns.include?(a) }
+      kode.uses.each { |use| (@uses << use) unless (@assigns.include?(use) or @uses.include?(use)) }
+      #puts "IN ADD #{name}#{uses}" 
+      @codes << kode
+    end
     alias :<< :add_code 
 
     # create a new linear block after this block. Linear means there is no brach needed from this one
@@ -85,6 +98,13 @@ module Vm
       add_code RegisterMachine.instance.send(meth , *args)
     end
 
+    # returns if this is a block that ends in a call (and thus needs local variable handling)
+    def call_block?
+      return false unless codes.last.is_a?(CallInstruction)
+      return false unless codes.last.opcode == :call
+      codes.dup.reverse.find{ |c| c.is_a? StackInstruction }
+    end
+
     # Code interface follows. Note position is inheitted as is from Code
 
     # length of the block is the length of it's codes, plus any next block (ie no branch follower)
@@ -116,5 +136,19 @@ module Vm
       end
       @next.assemble(io) if @next
     end
+
+    private
+    def add_next ret
+      return if @next.nil?
+      return if ret.include? @next
+      ret << @next
+      ret + @next.reachable
+    end
+    def add_branch ret
+      return if @branch.nil?
+      return if ret.include? @branch
+      ret << @branch
+      ret + @branch.reachable
+    end
   end
 end

lib/vm/function.rb

@@ -56,7 +56,7 @@ module Vm
       @body =  Block.new("body", self , @return)
       @entry = Core::Kernel::function_entry( Vm::Block.new("entry" , self , @body) ,name )
       @locals = []
-      @blocks = []
+      @linked = false # incase link is called twice, we only calculate locals once
     end
 
     attr_reader :args , :entry , :exit , :body , :name , :return_type , :receiver
@@ -81,46 +81,53 @@ module Vm
       @locals << l
       l
     end
-    #BUG - must save receiver
     
-    def save_locals context , into
-      save = args.collect{|a| a.register_symbol } + @locals.collect{|l| l.register_symbol}
-      into.push(save) unless save.empty?
-    end
-
-    def restore_locals context , into
-      #TODO assumes allocation in order, as the pop must be get regs in ascending order (also push)
-      restore = args.collect{|a| a.register_symbol } + @locals.collect{|l| l.register_symbol}
-      into.pop(restore) unless restore.empty?
-    end
-
-    def new_block name
-      block = Block.new(name , self)
-      @blocks << block
-      block
+    # return a list of registers that are still in use after the given block
+    # a call_site uses pushes and pops these to make them available for code after a call
+    def locals_at l_block
+      used =[]
+      assigned = []
+      l_block.reachable.each do |b|
+        b.uses.each {|u|
+          (used << u) unless assigned.include?(u) 
+        }
+        assigned += b.assigns
+      end
+      used.uniq
     end
 
     # return a list of the blocks that are addressable, ie entry and @blocks and all next
     def blocks
       ret = []
-      (@blocks << @entry).each do |b|
-        while b
-          ret << b
-          b = b.next
-        end  
-      end
+      b = @entry
+      while b
+        ret << b
+        b = b.next
+      end  
       ret
     end
+
     # following id the Code interface
     
     # to link we link the entry and then any blocks. The entry links the straight line
     def link_at address , context
       super #just sets the position
       @entry.link_at address , context
-      address += @entry.length
-      @blocks.each do |block|
-        block.link_at(pos , context)
-        pos += block.length
+      return if @linked
+      @linked = true
+      blocks.each do |b|
+        if push = b.call_block?
+          locals = locals_at b
+          if(locals.empty?)
+            puts "Empty #{b}"
+          else
+            puts "PUSH #{push}"
+            push.set_registers(locals)
+            pop = b.next.codes.first
+            puts "POP #{pop}"
+            pop.set_registers(locals)
+          end
+        end
       end
     end
 
@@ -132,16 +139,12 @@ module Vm
     # length of a function is the entry block length (includes the straight line behind it) 
     # plus any out of line blocks that have been added
     def length
-      @blocks.inject(@entry.length) {| sum  , item | sum + item.length}
+      @entry.length
     end
     
     # assembling assembles the entry (straight line/ no branch line) + any additional branches
     def assemble io
       @entry.assemble(io)
-      @blocks.each do |block|
-        block.assemble io
-      end
     end
-
   end
 end

lib/vm/instruction.rb

@@ -62,6 +62,10 @@ module Vm
       @first = first
       super(options)
     end
+    # when calling we place a dummy push/pop in the stream and calculate later what registers actually need saving 
+    def set_registers regs
+      @first = regs.collect{ |r| r.symbol }
+    end
     def is_push?
       opcode == :push
     end

lib/vm/meta_class.rb

@@ -27,16 +27,16 @@ module Vm
     def get_function name
       name = name.to_sym
       f = @functions.detect{ |f| f.name == name }
-      puts "no function for #{name} in Meta #{@me_self.inspect}" unless f
+      puts "no function for :#{name} in Meta #{@me_self.inspect}" unless f
       f
     end
     # way of creating new functions that have not been parsed.
     def get_or_create_function name 
       fun = get_function name
       unless fun or name == :Object
-        supr = @context.object_space.get_or_create_class(@super_class)
+        supr = @me_self.context.object_space.get_or_create_class(@super_class)
         fun = supr.get_function name
-        puts "#{supr.functions.collect(&:name)} for #{name} GOT #{fun.class}" if name == :index_of
+        puts "#{supr.functions.collect(&:name)} for #{name} GOT #{fun.class}"
       end
       fun
     end