PPC: [for-in] Ensure that we learn from deopts within for-in loop bodies.

src/full-codegen/ppc/full-codegen-ppc.cc

Index: src/full-codegen/ppc/full-codegen-ppc.cc
diff --git a/src/full-codegen/ppc/full-codegen-ppc.cc b/src/full-codegen/ppc/full-codegen-ppc.cc
index 0abae3d6271892fc18a4ede5d3e7087740b0ca9b..a309d12fd0df4235cf7ac03663b33dc23b8417f6 100644
--- a/src/full-codegen/ppc/full-codegen-ppc.cc
+++ b/src/full-codegen/ppc/full-codegen-ppc.cc
@@ -1076,9 +1076,9 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   // We got a fixed array in register r3. Iterate through that.
   __ bind(&fixed_array);
 
+  int const vector_index = SmiFromSlot(slot)->value();
   __ EmitLoadTypeFeedbackVector(r4);
   __ mov(r5, Operand(TypeFeedbackVector::MegamorphicSentinel(isolate())));
-  int vector_index = SmiFromSlot(slot)->value();
   __ StoreP(
       r5, FieldMemOperand(r4, FixedArray::OffsetOfElementAt(vector_index)), r0);
   __ LoadSmiLiteral(r4, Smi::FromInt(1));  // Smi(1) indicates slow check
@@ -1117,6 +1117,17 @@ void FullCodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   __ cmp(r7, r5);
   __ beq(&update_each);
 
+  // We might get here from TurboFan or Crankshaft when something in the
+  // for-in loop body deopts and only now notice in fullcodegen, that we
+  // can now longer use the enum cache, i.e. left fast mode. So better record
+  // this information here, in case we later OSR back into this loop or
+  // reoptimize the whole function w/o rerunning the loop with the slow
+  // mode object in fullcodegen (which would result in a deopt loop).
+  __ EmitLoadTypeFeedbackVector(r3);
+  __ mov(r5, Operand(TypeFeedbackVector::MegamorphicSentinel(isolate())));
+  __ StoreP(
+      r5, FieldMemOperand(r3, FixedArray::OffsetOfElementAt(vector_index)), r0);
+
   // Convert the entry to a string or (smi) 0 if it isn't a property
   // any more. If the property has been removed while iterating, we
   // just skip it.