Move the ctrl_typevar function into dfg.

Soon, InstructionData won't have sufficient information to compute this.

Give TargetIsa::encode() an explicit ctrl_typevar argument. This
function does not require the instruction to be inserted in the DFG
tables.

lib/cretonne/src/isa/intel/mod.rs

@@ -60,10 +60,11 @@ impl TargetIsa for Isa {
     }
 
     fn encode(&self,
-              dfg: &ir::DataFlowGraph,
-              inst: &ir::InstructionData)
+              _dfg: &ir::DataFlowGraph,
+              inst: &ir::InstructionData,
+              ctrl_typevar: ir::Type)
               -> Result<Encoding, Legalize> {
-        lookup_enclist(inst.ctrl_typevar(dfg),
+        lookup_enclist(ctrl_typevar,
                        inst.opcode(),
                        self.cpumode,
                        &enc_tables::LEVEL2[..])