Reland "Add basic crankshaft support for slow-mode for-in to avoid disabling optimizations"

src/mips64/lithium-codegen-mips64.cc

Index: src/mips64/lithium-codegen-mips64.cc
diff --git a/src/mips64/lithium-codegen-mips64.cc b/src/mips64/lithium-codegen-mips64.cc
index 2e6ede54aeaeeecf54c866308db28b2671d41629..7df1676ef285a45a2dc9b896ec679075d626e411 100644
--- a/src/mips64/lithium-codegen-mips64.cc
+++ b/src/mips64/lithium-codegen-mips64.cc
@@ -5880,12 +5880,6 @@ void LCodeGen::DoOsrEntry(LOsrEntry* instr) {
 void LCodeGen::DoForInPrepareMap(LForInPrepareMap* instr) {
   Register result = ToRegister(instr->result());
   Register object = ToRegister(instr->object());
-  __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
-  DeoptimizeIf(eq, instr, Deoptimizer::kUndefined, object, Operand(at));
-
-  Register null_value = a5;
-  __ LoadRoot(null_value, Heap::kNullValueRootIndex);
-  DeoptimizeIf(eq, instr, Deoptimizer::kNull, object, Operand(null_value));
 
   __ And(at, object, kSmiTagMask);
   DeoptimizeIf(eq, instr, Deoptimizer::kSmi, at, Operand(zero_reg));
@@ -5897,6 +5891,8 @@ void LCodeGen::DoForInPrepareMap(LForInPrepareMap* instr) {
 
   Label use_cache, call_runtime;
   DCHECK(object.is(a0));
+  Register null_value = a5;
+  __ LoadRoot(null_value, Heap::kNullValueRootIndex);
   __ CheckEnumCache(null_value, &call_runtime);
 
   __ ld(result, FieldMemOperand(object, HeapObject::kMapOffset));