Tag length of FixedArrayBase and smi-array[x] as smi representation

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 135c4cf3f9fe19f5c6d0caa52f9df677e199b4d6..51845724cebd2a2c9dc09ce3d6d379bce9caf827 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1815,6 +1815,12 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
   if (from.IsSmi()) {
     if (to.IsTagged()) {
       LOperand* value = UseRegister(instr->value());
+      // For now, always deopt on hole.
+      if (instr->value()->IsLoadKeyed() &&
+          HLoadKeyed::cast(instr->value())->UsesMustHandleHole()) {
+        return AssignEnvironment(
+            DefineSameAsFirst(new(zone()) LCheckSmiAndReturn(value)));
+      }
       return DefineSameAsFirst(new(zone()) LDummyUse(value));
     }
     from = Representation::Tagged();
@@ -1830,9 +1836,9 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       return AssignEnvironment(DefineAsRegister(res));
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
-      LOperand* value = UseRegisterAtStart(val);
+      LOperand* value = UseRegister(val);
       return AssignEnvironment(
-          DefineSameAsFirst(new(zone()) LCheckSmi(value)));
+          DefineSameAsFirst(new(zone()) LCheckSmiAndReturn(value)));
     } else {
       ASSERT(to.IsInteger32());
       LOperand* value = UseRegister(instr->value());
@@ -1937,13 +1943,13 @@ LInstruction* LChunkBuilder::DoCheckPrototypeMaps(HCheckPrototypeMaps* instr) {
 
 LInstruction* LChunkBuilder::DoCheckSmi(HCheckSmi* instr) {
   LOperand* value = UseRegisterAtStart(instr->value());
-  return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));
+  return AssignEnvironment(new(zone()) LCheckSmi(value));
 }
 
 
 LInstruction* LChunkBuilder::DoCheckSmiOrInt32(HCheckSmiOrInt32* instr) {
   LOperand* value = UseRegisterAtStart(instr->value());
-  return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));
+  return AssignEnvironment(new(zone()) LCheckSmi(value));
 }