Make sure to never wipe out the type of already used expression such …

…as the stack pointer.

src/util.js

@@ -12,6 +12,7 @@
   const BinaryExpression = T.BinaryExpression;
   const Literal = T.Literal;
   const MemberExpression = T.MemberExpression;
+  const SequenceExpression = T.SequenceExpression;
 
 
   function realign(expr, lalign) {
@@ -49,6 +50,7 @@
 
   function dereference(address, byteOffset, ty, scope, loc) {
     assert(scope);
+    address = copy(address, address.ty);
     address = alignAddress(address, byteOffset, ty);
     var expr;
     if (ty instanceof Types.ArrayType) {
@@ -136,6 +138,12 @@
     return node;
   }
 
+  function copy(node, ty) {
+    node = new SequenceExpression([node], node.loc);
+    node.ty = ty;
+    return node;
+  }
+
   var OptParser = (function () {
     function OptParser(flatspec) {
       // ['a', 'arg', default, 'help string']