Don't MISS if you read the hole from certain FastHoley arrays.

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index acc647d793c8bb0f020ecc6ab89895decb283ecd..3ec267de3577711215f6f47d5717fef87fa5be29 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -3614,6 +3614,21 @@ void LCodeGen::DoLoadKeyedFixed(LLoadKeyedFixed* instr) {
       DeoptimizeIfRoot(result, Heap::kTheHoleValueRootIndex, instr,
                        Deoptimizer::kHole);
     }
+  } else if (instr->hydrogen()->hole_mode() == CONVERT_HOLE_TO_UNDEFINED) {
+    DCHECK(instr->hydrogen()->elements_kind() == FAST_HOLEY_ELEMENTS);
+    Label done;
+    __ CompareRoot(result, Heap::kTheHoleValueRootIndex);
+    __ B(ne, &done);
+    if (info()->IsStub()) {
+      // A stub can safely convert the hole to undefined only if the array
+      // protector cell contains (Smi) 1. Otherwise it needs to bail out.
+      __ LoadRoot(result, Heap::kArrayProtectorRootIndex);
+      __ ldr(result, FieldMemOperand(result, Cell::kValueOffset));

[Jakob Kummerow, 2015/04/23 13:40:00]

nit: s/ldr/Ldr/ (always use MacroAssembler instructions on arm64).

[mvstanton, 2015/04/27 07:57:12]

Done.

+      __ Cmp(result, Operand(Smi::FromInt(1)));
+      DeoptimizeIf(ne, instr, Deoptimizer::kHole);
+    }
+    __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
+    __ bind(&done);

[Jakob Kummerow, 2015/04/23 13:40:00]

nit: s/bind/Bind/

[mvstanton, 2015/04/27 07:57:12]

Done.

   }
 }