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

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index 564ef0046ab5fed77d89fbfd7b7597d284721cf7..37f8bccd1d7d0ccaa996d425e68521a7fd5675d0 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -3184,6 +3184,21 @@ void LCodeGen::DoLoadKeyedFixedArray(LLoadKeyed* instr) {
       __ cmp(result, factory()->the_hole_value());
       DeoptimizeIf(equal, instr, Deoptimizer::kHole);
     }
+  } else if (instr->hydrogen()->hole_mode() == CONVERT_HOLE_TO_UNDEFINED) {
+    DCHECK(instr->hydrogen()->elements_kind() == FAST_HOLEY_ELEMENTS);
+    Label done;
+    __ cmp(result, factory()->the_hole_value());
+    __ j(not_equal, &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.
+      __ mov(result, isolate()->factory()->array_protector());

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

You can collapse this into one instruction:

__ cmp(Operand::ForCell(isolate()->factory()->array_protector()),
       Immediate(Smi::FromInt(1)));

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

Actually I can't do that for a PropertyCell, just a Cell. Cool idea though, I
didn't know about that instruction!

+      __ cmp(FieldOperand(result, Cell::kValueOffset),
+             Immediate(Smi::FromInt(1)));

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

Please factor out the magic 0/1 constants as "static const int
kArrayProtectorValid = 1" (in class Isolate) or similar.

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

Done.

+      DeoptimizeIf(not_equal, instr, Deoptimizer::kHole);
+    }
+    __ mov(result, isolate()->factory()->undefined_value());
+    __ bind(&done);
   }
 }