[interpreter] Heal closures when bytecode array is gone.

src/x64/builtins-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 614 matching lines @@
   // Open a frame scope to indicate that there is a frame on the stack.  The
   // MANUAL indicates that the scope shouldn't actually generate code to set up
   // the frame (that is done below).
   FrameScope frame_scope(masm, StackFrame::MANUAL);
   __ pushq(rbp);  // Caller's frame pointer.
   __ movp(rbp, rsp);
   __ Push(rsi);  // Callee's context.
   __ Push(rdi);  // Callee's JS function.
   __ Push(rdx);  // Callee's new target.
 
-  // Get the bytecode array from the function object and load the pointer to the
-  // first entry into edi (InterpreterBytecodeRegister).
+  // Get the bytecode array from the function object (or from the DebugInfo if
+  // it is present) and load it into kInterpreterBytecodeArrayRegister.
   __ movp(rax, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
-
   Label load_debug_bytecode_array, bytecode_array_loaded;
   DCHECK_EQ(Smi::FromInt(0), DebugInfo::uninitialized());
   __ cmpp(FieldOperand(rax, SharedFunctionInfo::kDebugInfoOffset),
           Immediate(0));
   __ j(not_equal, &load_debug_bytecode_array);
   __ movp(kInterpreterBytecodeArrayRegister,
           FieldOperand(rax, SharedFunctionInfo::kFunctionDataOffset));
   __ bind(&bytecode_array_loaded);
 
+  // Check function data field is actually a BytecodeArray object.
+  Label bytecode_array_not_present;
+  __ CompareRoot(kInterpreterBytecodeArrayRegister,
+                 Heap::kUndefinedValueRootIndex);
+  __ j(equal, &bytecode_array_not_present);
   if (FLAG_debug_code) {
-    // Check function data field is actually a BytecodeArray object.
     __ AssertNotSmi(kInterpreterBytecodeArrayRegister);
     __ CmpObjectType(kInterpreterBytecodeArrayRegister, BYTECODE_ARRAY_TYPE,
                      rax);
     __ Assert(equal, kFunctionDataShouldBeBytecodeArrayOnInterpreterEntry);
   }
 
   // Push bytecode array.
   __ Push(kInterpreterBytecodeArrayRegister);
   // Push zero for bytecode array offset.
   __ Push(Immediate(0));
@@ skipping 48 matching lines @@
   // Even though the first bytecode handler was called, we will never return.
   __ Abort(kUnexpectedReturnFromBytecodeHandler);
 
   // Load debug copy of the bytecode array.
   __ bind(&load_debug_bytecode_array);
   Register debug_info = kInterpreterBytecodeArrayRegister;
   __ movp(debug_info, FieldOperand(rax, SharedFunctionInfo::kDebugInfoOffset));
   __ movp(kInterpreterBytecodeArrayRegister,
           FieldOperand(debug_info, DebugInfo::kAbstractCodeIndex));
   __ jmp(&bytecode_array_loaded);
+
+  // 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);
+  __ leave();  // Leave the frame so we can tail call.
+  __ movp(rcx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+  __ movp(rcx, FieldOperand(rcx, SharedFunctionInfo::kCodeOffset));
+  __ leap(rcx, FieldOperand(rcx, Code::kHeaderSize));
+  __ movp(FieldOperand(rdi, JSFunction::kCodeEntryOffset), rcx);
+  __ RecordWriteCodeEntryField(rdi, rcx, r15);
+  __ jmp(rcx);
 }
 
 
 void Builtins::Generate_InterpreterExitTrampoline(MacroAssembler* masm) {
   // The return value is in accumulator, which is already in rax.
 
   // Leave the frame (also dropping the register file).
   __ leave();
 
   // Drop receiver + arguments and return.
@@ skipping 2189 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64