Merged r17441 into 3.21 branch.

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 d9daaacca0bbbdbb29f79756ebb330d1ddf5524e..a0e853d4fc374e6bbd12545f1041e03ff3146823 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1899,10 +1899,18 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
-      LInstruction* result =
-          DefineAsRegister(new(zone()) LInteger32ToSmi(value));
-      if (val->HasRange() && val->range()->IsInSmiRange()) {
-        return result;
+      LInstruction* result = NULL;
+      if (val->CheckFlag(HInstruction::kUint32)) {
+        result = DefineAsRegister(new(zone()) LUint32ToSmi(value));
+        if (val->HasRange() && val->range()->IsInSmiRange() &&
+            val->range()->upper() != kMaxInt) {
+          return result;
+        }
+      } else {
+        result = DefineAsRegister(new(zone()) LInteger32ToSmi(value));
+        if (val->HasRange() && val->range()->IsInSmiRange()) {
+          return result;
+        }
       }
       return AssignEnvironment(result);
     } else {