microinstruction: Identity's type depends on the type of its argument

src/frontend/ir/microinstruction.cpp

@@ -214,6 +214,12 @@ bool Inst::MayHaveSideEffects() const {
 
 }
 
+Type Inst::GetType() const {
+    if (op == Opcode::Identity)
+        return args[0].GetType();
+    return GetTypeOf(op);
+}
+
 Value Inst::GetArg(size_t index) const {
     DEBUG_ASSERT(index < GetNumArgsOf(op));
     DEBUG_ASSERT(!args[index].IsEmpty());

src/frontend/ir/microinstruction.h

@@ -78,7 +78,7 @@ public:
     /// Get the microop this microinstruction represents.
     Opcode GetOpcode() const { return op; }
     /// Get the type this instruction returns.
-    Type GetType() const { return GetTypeOf(op); }
+    Type GetType() const;
     /// Get the number of arguments this instruction has.
     size_t NumArgs() const { return GetNumArgsOf(op); }