X87: Reland "Add basic crankshaft support for slow-mode for-in to avoid disabling optimizations"

src/x87/lithium-codegen-x87.cc

Index: src/x87/lithium-codegen-x87.cc
diff --git a/src/x87/lithium-codegen-x87.cc b/src/x87/lithium-codegen-x87.cc
index ed5b9d666081e0597349e965c56b74454b798642..a70155367d2468ddca23b37d825a238d10a679e6 100644
--- a/src/x87/lithium-codegen-x87.cc
+++ b/src/x87/lithium-codegen-x87.cc
@@ -6206,12 +6206,6 @@ void LCodeGen::DoOsrEntry(LOsrEntry* instr) {
 
 void LCodeGen::DoForInPrepareMap(LForInPrepareMap* instr) {
   DCHECK(ToRegister(instr->context()).is(esi));
-  __ cmp(eax, isolate()->factory()->undefined_value());
-  DeoptimizeIf(equal, instr, Deoptimizer::kUndefined);
-
-  __ cmp(eax, isolate()->factory()->null_value());
-  DeoptimizeIf(equal, instr, Deoptimizer::kNull);
-
   __ test(eax, Immediate(kSmiTagMask));
   DeoptimizeIf(zero, instr, Deoptimizer::kSmi);