diff --git a/llvm_emulator/stepper.py b/llvm_emulator/stepper.py
index 61cf031..aeb641d 100644
--- a/llvm_emulator/stepper.py
+++ b/llvm_emulator/stepper.py
@@ -25,6 +25,9 @@ class Garbage(Enum):
         return '<<Garbage>>'
 
 
+builtins = ['allocRecord', 'initArray']
+
+
 def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
          tdecs, fdecs, call_res):
     if len(insns) == 0:
@@ -33,6 +36,23 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
     ssa_target, next_insn = insns[0]
     insns_rest = insns[1:]
 
+    def store_in_ssa(res, insns_rest, terminator, blocks, stack_frames, ssa_env, heap,
+                     call_res):
+        if ssa_target is not None:
+            if ssa_target in ssa_env:
+                err('Cannot assign to variable twice: {}'
+                    .format(ssa_target))
+            elif res is None:
+                err('Cannot assign empty value to %{}'
+                    .format(ssa_target))
+            else:
+                # TODO
+                print('%{} <- {}'
+                      .format(ssa_target, res))
+                ssa_env[ssa_target] = res
+
+        return insns_rest, terminator, blocks, stack_frames, ssa_env, heap, call_res
+
     # TODO
     print('Evaluating {}'
           .format(ll.insn2s(next_insn)))
@@ -128,11 +148,26 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
         arguments_v = [eval_oper(oper, ssa_env, global_env)
                        for ty, oper in arguments]
 
-        try:
+        if callee.val in fdecs:
             function = fdecs[callee.val]
-        except KeyError:
+        elif callee.val in builtins:
+            res, new_heap, should_exit = emulate_builtin(callee.val, arguments_v, ssa_env,
+                                                         heap)
+            if should_exit:
+                new_insns = [(None, ll.CallResult(res))]
+                new_terminator = None
+                new_blocks = {}
+                new_ssa_env = ssa_env
+                new_stack_frames = []
+                new_call_res = []
+                return (new_insns, new_terminator, new_blocks, new_stack_frames,
+                        new_ssa_env, heap, new_call_res)
+            else:
+                return store_in_ssa(res, insns_rest, terminator, blocks, stack_frames,
+                                    ssa_env, new_heap, call_res)
+        else:
             err('Could not find function {} in environment:\n{}'
-                .format(callee.val, list(fdecs.keys())))
+                .format(callee.val, list(fdecs.keys()) + builtins))
             return insns_rest, terminator, blocks, stack_frames, ssa_env, heap, call_res
 
         parameters = function.parameters
@@ -214,20 +249,8 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
         err('Unknown LLVM instruction: {}'
             .format(next_insn))
 
-    if ssa_target is not None:
-        if ssa_target in ssa_env:
-            err('Cannot assign to variable twice: {}'
-                .format(ssa_target))
-        elif res is None:
-            err('Cannot assign empty value to %{}'
-                .format(ssa_target))
-        else:
-            # TODO
-            print('%{} <- {}'
-                  .format(ssa_target, res))
-            ssa_env[ssa_target] = res
-
-    return insns_rest, terminator, blocks, stack_frames, ssa_env, heap, call_res
+    return store_in_ssa(res, insns_rest, terminator, blocks, stack_frames, ssa_env, heap,
+                        call_res)
 
 
 def terminate(terminator, blocks, stack_frames, ssa_env, global_env, heap, call_res):
@@ -503,6 +526,71 @@ def alloc_globals(gdecls, heap):
     return global_env
 
 
+def emulate_builtin(name, arguments_v, ssa_env, heap):
+    new_heap = heap
+    res = None
+    should_exit = False
+    if name == 'allocRecord':
+        if len(arguments_v) != 1:
+            err('Number of arguments to {} should be 1'
+                .format(name))
+        else:
+            size = max(arguments_v[0], 1)
+            print('Allocating {} cells'
+                  .format(size))
+            res = len(heap)
+            for i in range(size):
+                heap.append(Garbage.GARBAGE)
+    elif name == 'initArray':
+        if len(arguments_v) != 3:
+            err('Number of arguments to {} should be 3'
+                .format(name))
+        else:
+            num_elements = arguments_v[0]
+            cells_per_element = arguments_v[1]
+            init_ptr = arguments_v[2]
+            print('Allocating {} + {} + {} (size + pointer + content) cells'
+                  .format(1, 1, num_elements * cells_per_element))
+            struct_begin = len(heap)
+            heap.append(num_elements)
+            heap.append(Garbage.GARBAGE)  # pointer to array contents
+            array_begin = len(heap)
+            heap[struct_begin + 1] = array_begin
+            init_val = [heap[init_ptr + j]
+                        for j in range(cells_per_element)]
+            if len(init_val) == 1:
+                init_val_s = init_val[0]
+            else:
+                init_val_s = '{{}}'.format(', '.join(init_val))
+
+            for i in range(num_elements):
+                array_last = len(heap)
+                for j in init_val:
+                    heap.append(j)
+
+            if num_elements <= 0:
+                array_init_s = 'No elements initialized for zero length array'
+            else:
+                array_init_s = ('heap[{}..{}] <- heap[{}] = {}'
+                                .format(array_begin, array_last,
+                                        init_ptr, init_val_s))
+            # TODO
+            print('heap[{}] <- {}, heap[{}] <- {}, --- {}'
+                  .format(struct_begin, num_elements,
+                          struct_begin + 1, array_begin,
+                          array_init_s))
+            res = struct_begin
+    elif name in builtins:
+        TODO('Have not implemented builtin function {}, yet.'
+             .format(name))
+    else:
+        err('Unknown builtin function {}.'
+            .format(name))
+        return None, heap
+
+    return res, new_heap, should_exit
+
+
 def auto_step(ast, function_name='tigermain', function_args=[1234, 5678]):
     tdecls = ast.tdecls
     fdecls = ast.fdecls