change platform to return register names

not just the number of them
also adds protocol to map registers
(like message to r0 , or syscalls)

lib/risc/platform.rb

@@ -8,17 +8,19 @@ module Risc
     # return the translator instance that traslates risc intructions into
     # platform specific ones
     def translator
-      raise "not implemented"
+      raise "not implemented in #{self.class}"
     end
 
     # return an integer where the binary is loaded
     def loaded_at
-      raise "not implemented"
+      raise "not implemented in #{self.class}"
     end
 
-    # return the number of registers the platform supports
-    def num_registers
-      raise "not implemented"
+    # return an array of register names that should be used by the allocator
+    # does not include :message
+    # could be in interpreter and arm, but here for now
+    def register_names
+      (1 ... 16).collect{|i| "r#{i}".to_sym }
     end
 
     # return the Allocator for the platform
@@ -30,6 +32,19 @@ module Risc
       StandardAllocator.new(compiler , self )
     end
 
+    def assign_reg?(name)
+      case name
+      when :message
+        :r0
+      when :syscall_1
+        :r0
+      when :syscall_2
+        :r1
+      else
+        nil
+      end
+    end
+
     # Factory method to create a Platform object according to the platform
     # string given.
     # Currently only "Arm" and "Interpreter"

lib/risc/standard_allocator.rb

@@ -14,7 +14,7 @@ module Risc
       @platform = platform
       @used_regs = {}
       @release_points = Hash.new {|hash , key | hash[key] = [] }
-      @reg_names = (0 ... platform.num_registers).collect{|i| "r#{i}".to_sym }
+      @reg_names = platform.register_names
     end
     attr_reader :used_regs , :compiler , :platform , :reg_names
 
@@ -49,9 +49,11 @@ module Risc
 
     def assign(instruction)
       names = instruction.register_names
-      names.each do |for_name|
-        new_reg = get_reg(for_name)
+      #puts "AT #{instruction}"
+      names.each do |ssa_name|
+        new_reg = get_reg(ssa_name)
         # swap name out
+        #puts "Assign #{new_reg} for #{ssa_name}"
       end
       names
     end
@@ -76,10 +78,6 @@ module Risc
       released
     end
 
-    def used_regs_empty?
-      @used_regs.empty?
-    end
-
     # use the given reg (first) parameter and mark it as assigned to
     # it's ssa form, the second parameter.
     # forward check is trivial, and reverse_used provides reverse check
@@ -88,6 +86,7 @@ module Risc
       raise "Stupid error #{reg}" unless reg.is_a?(Symbol)
       #puts "Using #{reg} for #{ssa_name}"
       @used_regs[reg] = ssa_name
+      reg
     end
 
     # Check whether a register has been assigned to the given ssa form given.
@@ -104,6 +103,12 @@ module Risc
     def get_reg(ssa_name)
       name = reverse_used( ssa_name )
       return name if name
+      get_next_free(ssa_name)
+    end
+
+    def get_next_free(ssa_name)
+      reg = platform.assign_reg?( ssa_name )
+      return use_reg(reg , ssa_name) if reg
       @reg_names.each do |name|
         return use_reg(name , ssa_name) unless @used_regs.has_key?(name)
       end