1 files changed, 19 insertions, 5 deletions
diff --git a/tool/ruby_vm/models/bare_instructions.rb b/tool/ruby_vm/models/bare_instructions.rb
index 7d9ed6da5a..2767f383e6 100755
--- a/tool/ruby_vm/models/bare_instructions.rb
+++ b/tool/ruby_vm/models/bare_instructions.rb
@@ -144,6 +144,7 @@ class RubyVM::BareInstructions
   end
 
   def predefine_attributes
+    # Beware: order matters here because some attribute depends another.
     generate_attribute 'const char*', 'name', "insn_name(#{bin})"
     generate_attribute 'enum ruby_vminsn_type', 'bin', bin
     generate_attribute 'rb_num_t', 'open', opes.size
@@ -151,11 +152,24 @@ class RubyVM::BareInstructions
     generate_attribute 'rb_num_t', 'retn', rets.size
     generate_attribute 'rb_num_t', 'width', width
     generate_attribute 'rb_snum_t', 'sp_inc', rets.size - pops.size
-    generate_attribute 'bool', 'handles_sp', false
-    generate_attribute 'bool', 'leaf', opes.all? {|o|
-      # Insn with ISEQ should yield it; can never be a leaf.
-      o[:type] != 'ISEQ'
-    }
+    generate_attribute 'bool', 'handles_sp', default_definition_of_handles_sp
+    generate_attribute 'bool', 'leaf', default_definition_of_leaf
+  end
+
+  def default_definition_of_handles_sp
+    # Insn with ISEQ should yield it; can handle sp.
+    return opes.any? {|o| o[:type] == 'ISEQ' }
+  end
+
+  def default_definition_of_leaf
+    # Insn that handles SP can never be a leaf.
+    if not has_attribute? 'handles_sp' then
+      return ! default_definition_of_handles_sp
+    elsif handles_sp? then
+      return "! #{call_attribute 'handles_sp'}"
+    else
+      return true
+    end
   end
 
   def typesplit a