diff --git a/artiq/compiler/ir_ast_body.py b/artiq/compiler/ir_ast_body.py
index 7ac1c8846..ced70968a 100644
--- a/artiq/compiler/ir_ast_body.py
+++ b/artiq/compiler/ir_ast_body.py
@@ -1,11 +1,14 @@
 import ast
+from copy import copy
+
+from llvm import core as lc
 
 from artiq.compiler import ir_values
 
 class Visitor:
-	def __init__(self, builder, ns):
-		self.builder = builder
+	def __init__(self, ns, builder=None):
 		self.ns = ns
+		self.builder = builder
 
 	# builder can be None for visit_expression
 	def visit_expression(self, node):
@@ -17,7 +20,17 @@ class Visitor:
 		return visitor(node)
 
 	def _visit_expr_Name(self, node):
-		return self.ns.load(self.builder, node.id)
+		try:
+			r = self.ns[node.id]
+		except KeyError:
+			raise NameError("Name '{}' is not defined".format(node.id))
+		r = copy(r)
+		if self.builder is None:
+			r.llvm_value = None
+		else:
+			if isinstance(r.llvm_value, lc.AllocaInstruction):
+				r.llvm_value = self.builder.load(r.llvm_value)
+		return r
 
 	def _visit_expr_NameConstant(self, node):
 		v = node.value
@@ -112,14 +125,14 @@ class Visitor:
 		val = self.visit_expression(node.value)
 		for target in node.targets:
 			if isinstance(target, ast.Name):
-				self.ns.store(self.builder, val, target.id)
+				self.builder.store(val, self.ns[target.id])
 			else:
 				raise NotImplementedError
 
 	def _visit_stmt_AugAssign(self, node):
 		val = self.visit_expression(ast.BinOp(op=node.op, left=node.target, right=node.value))
 		if isinstance(node.target, ast.Name):
-			self.ns.store(self.builder, val, node.target.id)
+			self.builder.store(val, self.ns[node.target.id])
 		else:
 			raise NotImplementedError
 
diff --git a/artiq/compiler/ir_infer_types.py b/artiq/compiler/ir_infer_types.py
index 1d91f8c18..62f2e3c44 100644
--- a/artiq/compiler/ir_infer_types.py
+++ b/artiq/compiler/ir_infer_types.py
@@ -4,51 +4,43 @@ from copy import deepcopy
 
 from artiq.compiler.ir_ast_body import Visitor
 
-class _Namespace:
-	def __init__(self, name_to_value):
-		self.name_to_value = name_to_value
-
-	def load(self, builder, name):
-		return self.name_to_value[name]
-
 class _TypeScanner(ast.NodeVisitor):
-	def __init__(self, namespace):
-		self.exprv = Visitor(None, namespace)
+	def __init__(self, ns):
+		self.exprv = Visitor(ns)
 
 	def visit_Assign(self, node):
 		val = self.exprv.visit_expression(node.value)
-		n2v = self.exprv.ns.name_to_value
+		ns = self.exprv.ns
 		for target in node.targets:
 			if isinstance(target, ast.Name):
-				if target.id in n2v:
-					n2v[target.id].merge(val)
+				if target.id in ns:
+					ns[target.id].merge(val)
 				else:
-					n2v[target.id] = val
+					ns[target.id] = val
 			else:
 				raise NotImplementedError
 
 	def visit_AugAssign(self, node):
 		val = self.exprv.visit_expression(ast.BinOp(op=node.op, left=node.target, right=node.value))
-		n2v = self.exprv.ns.name_to_value
+		ns = self.exprv.ns
 		target = node.target
 		if isinstance(target, ast.Name):
-			if target.id in n2v:
-				n2v[target.id].merge(val)
+			if target.id in ns:
+				ns[target.id].merge(val)
 			else:
-				n2v[target.id] = val
+				ns[target.id] = val
 		else:
 			raise NotImplementedError
 
 def infer_types(node):
-	name_to_value = dict()
+	ns = dict()
 	while True:
-		prev_name_to_value = deepcopy(name_to_value)
-		ns = _Namespace(name_to_value)
+		prev_ns = deepcopy(ns)
 		ts = _TypeScanner(ns)
 		ts.visit(node)
-		if prev_name_to_value and all(v.same_type(prev_name_to_value[k]) for k, v in name_to_value.items()):
+		if prev_ns and all(v.same_type(prev_ns[k]) for k, v in ns.items()):
 			# no more promotions - completed
-			return name_to_value
+			return ns
 
 if __name__ == "__main__":
 	testcode = """
@@ -60,6 +52,6 @@ x = int64(7)
 a += x         # promotes a to int64
 foo = True
 """
-	n2v = infer_types(ast.parse(testcode))
-	for k, v in sorted(n2v.items(), key=itemgetter(0)):
+	ns = infer_types(ast.parse(testcode))
+	for k, v in sorted(ns.items(), key=itemgetter(0)):
 		print("{:10}-->   {}".format(k, str(v)))