PPC: [interpreter] Heal closures when bytecode array is gone.

Port 5c8609de

Original commit message:

    This ensures the InterpreterEntryTrampoline heals code entry fields
    inside closures when being called without a valid bytecode array. This
    is preparatory work to allow removal of bytecode when switching some
    functions to other types of code.

R=mstarzinger@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, mbrandy@us.ibm.com

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1913173002

Cr-Commit-Position: refs/heads/master@{#35739}

src/ppc/builtins-ppc.cc

@@ -999,8 +999,8 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ PushStandardFrame(r4);
 
-  // Get the bytecode array from the function object and load the pointer to the
-  // first entry into kInterpreterBytecodeRegister.
+  // Get the bytecode array from the function object (or from the DebugInfo if
+  // it is present) and load it into kInterpreterBytecodeArrayRegister.
   __ LoadP(r3, FieldMemOperand(r4, JSFunction::kSharedFunctionInfoOffset));
   Label array_done;
   Register debug_info = r5;
@@ -1016,8 +1016,13 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
            FieldMemOperand(debug_info, DebugInfo::kAbstractCodeIndex));
   __ bind(&array_done);
 
+  // Check function data field is actually a BytecodeArray object.
+  Label bytecode_array_not_present;
+  __ CompareRoot(kInterpreterBytecodeArrayRegister,
+                 Heap::kUndefinedValueRootIndex);
+  __ beq(&bytecode_array_not_present);
+
   if (FLAG_debug_code) {
-    // Check function data field is actually a BytecodeArray object.
     __ TestIfSmi(kInterpreterBytecodeArrayRegister, r0);
     __ Assert(ne, kFunctionDataShouldBeBytecodeArrayOnInterpreterEntry);
     __ CompareObjectType(kInterpreterBytecodeArrayRegister, r3, no_reg,
@@ -1076,6 +1081,18 @@ void Builtins::Generate_InterpreterEntryTrampoline(MacroAssembler* masm) {
 
   // Even though the first bytecode handler was called, we will never return.
   __ Abort(kUnexpectedReturnFromBytecodeHandler);
+
+  // If the bytecode array is no longer present, then the underlying function
+  // has been switched to a different kind of code and we heal the closure by
+  // switching the code entry field over to the new code object as well.
+  __ bind(&bytecode_array_not_present);
+  __ LeaveFrame(StackFrame::JAVA_SCRIPT);
+  __ LoadP(r7, FieldMemOperand(r4, JSFunction::kSharedFunctionInfoOffset));
+  __ LoadP(r7, FieldMemOperand(r7, SharedFunctionInfo::kCodeOffset));
+  __ addi(r7, r7, Operand(Code::kHeaderSize - kHeapObjectTag));
+  __ StoreP(r7, FieldMemOperand(r4, JSFunction::kCodeEntryOffset), r0);
+  __ RecordWriteCodeEntryField(r4, r7, r8);
+  __ JumpToJSEntry(r7);
 }