Handle holes in smi-untag from LoadKeyed requiring hole handling.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 9a1ce9800993d683dc04ea27bee12b54b70c9168..42c6e9148e71d6b5fe16dc810ac643efe43b8ce7 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4606,6 +4606,21 @@ void LCodeGen::DoSmiUntag(LSmiUntag* instr) {
   if (instr->needs_check()) {
     Condition is_smi = __ CheckSmi(input);
     DeoptimizeIf(NegateCondition(is_smi), instr->environment());
+  } else if (instr->hydrogen()->value()->IsLoadKeyed()) {
+    HLoadKeyed* load = HLoadKeyed::cast(instr->hydrogen()->value());
+    if (load->UsesMustHandleHole()) {
+      Condition cc = masm()->CheckSmi(input);
+      if (load->hole_mode() == ALLOW_RETURN_HOLE) {
+        Label done;
+        __ j(cc, &done);
+        __ xor_(input, input);
+        __ bind(&done);
+      } else {
+        DeoptimizeIf(NegateCondition(cc), instr->environment());
+      }
+    } else {
+      __ AssertSmi(input);
+    }
   } else {
     __ AssertSmi(input);
   }