Restrict immediate operands to smi where only smis are supported.

runtime/vm/locations.cc

Index: runtime/vm/locations.cc
===================================================================
--- runtime/vm/locations.cc	(revision 14796)
+++ runtime/vm/locations.cc	(working copy)
@@ -53,6 +53,14 @@
 }
 
 
+Location Location::RegisterOrSmiConstant(Value* value) {
+  ConstantInstr* constant = value->definition()->AsConstant();
+  return ((constant != NULL) && constant->value().IsSmi())
+      ? Location::Constant(constant->value())
+      : Location::RequiresRegister();
+}
+
+
 Location Location::FixedRegisterOrConstant(Value* value, Register reg) {
   ConstantInstr* constant = value->definition()->AsConstant();
   return (constant != NULL)
@@ -61,6 +69,14 @@
 }
 
 
+Location Location::FixedRegisterOrSmiConstant(Value* value, Register reg) {
+  ConstantInstr* constant = value->definition()->AsConstant();
+  return ((constant != NULL) && constant->value().IsSmi())
+      ? Location::Constant(constant->value())
+      : Location::RegisterLocation(reg);
+}
+
+
 const char* Location::Name() const {
   switch (kind()) {
     case kInvalid: return "?";