Reland "Fixed environment assignment for LCheckNonSmi."

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 90f9a1a236f72eb1b23dac9fcea4262acb986b43..ea5ef9f3af7b1736b51cfcda0533a41f787bd799 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1925,7 +1925,9 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
 
 LInstruction* LChunkBuilder::DoCheckHeapObject(HCheckHeapObject* instr) {
   LOperand* value = UseRegisterAtStart(instr->value());
-  return AssignEnvironment(new(zone()) LCheckNonSmi(value));
+  LInstruction* result = new(zone()) LCheckNonSmi(value);
+  if (!instr->value()->IsHeapObject()) result = AssignEnvironment(result);
+  return result;
 }