Eliminate Smi check when changing from Smi to Integer32

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 78c7b9c8d60836ea51e2d591efd676fd7da5c202..af4d96a290db9d4fe1de031560c8b632c354533d 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1801,10 +1801,14 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
   Representation from = instr->from();
   Representation to = instr->to();
   if (from.IsSmi()) {
-    if (to.IsTagged()) {
+    if (to.IsSmiOrTagged()) {
       LOperand* value = UseRegister(instr->value());
       return DefineSameAsFirst(new(zone()) LDummyUse(value));
     }
+    if (to.IsInteger32()) {
+      LOperand* value = UseRegister(instr->value());
+      return DefineSameAsFirst(new(zone()) LSmiUntag(value, false));
+    }
     from = Representation::Tagged();
   }
   // Only mark conversions that might need to allocate as calling rather than