Factor out common ways to call encode from a dfg or func.

lib/cretonne/src/ir/dfg.rs

@@ -1,7 +1,7 @@
 //! Data flow graph tracking Instructions, Values, and EBBs.
 
 use entity::{PrimaryMap, EntityMap};
-use isa::TargetIsa;
+use isa::{TargetIsa, Encoding, Legalize};
 use ir;
 use ir::builder::ReplaceBuilder;
 use ir::extfunc::ExtFuncData;
@@ -645,6 +645,12 @@ impl DataFlowGraph {
             self.value_type(self.first_result(inst))
         }
     }
+
+    /// Wrapper around `TargetIsa::encode` for encoding an existing instruction
+    /// in the `DataFlowGraph`.
+    pub fn encode(&self, inst: Inst, isa: &TargetIsa) -> Result<Encoding, Legalize> {
+        isa.encode(&self, &self[inst], self.ctrl_typevar(inst))
+    }
 }
 
 /// Allow immutable access to instructions via indexing.

lib/cretonne/src/ir/function.rs

@@ -10,7 +10,7 @@ use ir::{ExternalName, CallConv, Signature, DataFlowGraph, Layout};
 use ir::{InstEncodings, ValueLocations, JumpTables, StackSlots, EbbOffsets, SourceLocs};
 use ir::{Ebb, JumpTableData, JumpTable, StackSlotData, StackSlot, SigRef, ExtFuncData, FuncRef,
          GlobalVarData, GlobalVar, HeapData, Heap};
-use isa::{TargetIsa, EncInfo};
+use isa::{TargetIsa, EncInfo, Legalize};
 use std::fmt;
 use write::write_function;
 
@@ -176,6 +176,13 @@ impl Function {
             iter: self.layout.ebb_insts(ebb),
         }
     }
+
+    /// Wrapper around `DataFlowGraph::encode` which assigns `inst` the resulting encoding.
+    pub fn update_encoding(&mut self, inst: ir::Inst, isa: &TargetIsa) -> Result<(), Legalize> {
+        self.dfg.encode(inst, isa).map(
+            |e| { self.encodings[inst] = e; },
+        )
+    }
 }
 
 /// Wrapper type capable of displaying a `Function` with correct ISA annotations.

lib/cretonne/src/legalizer/mod.rs

@@ -72,12 +72,8 @@ pub fn legalize_function(func: &mut ir::Function, cfg: &mut ControlFlowGraph, is
                 split::simplify_branch_arguments(&mut pos.func.dfg, inst);
             }
 
-            match isa.encode(
-                &pos.func.dfg,
-                &pos.func.dfg[inst],
-                pos.func.dfg.ctrl_typevar(inst),
-            ) {
-                Ok(encoding) => pos.func.encodings[inst] = encoding,
+            match pos.func.update_encoding(inst, isa) {
+                Ok(()) => {}
                 Err(action) => {
                     // We should transform the instruction into legal equivalents.
                     let changed = action(inst, pos.func, cfg, isa);

lib/cretonne/src/verifier/mod.rs

@@ -1058,11 +1058,7 @@ impl<'a> Verifier<'a> {
         if let Some(text) = needs_enc {
             // This instruction needs an encoding, so generate an error.
             // Provide the ISA default encoding as a hint.
-            match isa.encode(
-                &self.func.dfg,
-                &self.func.dfg[inst],
-                self.func.dfg.ctrl_typevar(inst),
-            ) {
+            match self.func.dfg.encode(inst, isa) {
                 Ok(enc) => {
                     return err!(
                         inst,