[interpreter] Heal closures when bytecode array is gone.

src/ia32/builtins-ia32.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_IA32
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 536 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);
   __ push(ebp);  // Caller's frame pointer.
   __ mov(ebp, esp);
   __ push(esi);  // Callee's context.
   __ push(edi);  // Callee's JS function.
   __ push(edx);  // 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 edi (InterpreterBytecodeArrayRegister).
+  Label load_debug_bytecode_array, bytecode_array_loaded;
   __ mov(eax, FieldOperand(edi, JSFunction::kSharedFunctionInfoOffset));
-
-  Label load_debug_bytecode_array, bytecode_array_loaded;
   __ cmp(FieldOperand(eax, SharedFunctionInfo::kDebugInfoOffset),
          Immediate(DebugInfo::uninitialized()));
   __ j(not_equal, &load_debug_bytecode_array);
   __ mov(kInterpreterBytecodeArrayRegister,
          FieldOperand(eax, SharedFunctionInfo::kFunctionDataOffset));
   __ bind(&bytecode_array_loaded);
 
-  if (FLAG_debug_code) {
-    // Check function data field is actually a BytecodeArray object.
-    __ AssertNotSmi(kInterpreterBytecodeArrayRegister);
-    __ CmpObjectType(kInterpreterBytecodeArrayRegister, BYTECODE_ARRAY_TYPE,
-                     eax);
-    __ Assert(equal, kFunctionDataShouldBeBytecodeArrayOnInterpreterEntry);
-  }
+  // Check function data field is actually a BytecodeArray object.
+  Label bytecode_array_not_present;
+  __ JumpIfSmi(kInterpreterBytecodeArrayRegister, &bytecode_array_not_present);

[rmcilroy, 2016/04/21 15:16:02]

Maybe you could just compare with undefined to check for it not being present,
and keep the debug code assert only if the object is not undefined - I think
that would be slightly more efficient, WDYT?

[Michael Starzinger, 2016/04/21 15:43:08]

Done. Good point.

+  __ CmpObjectType(kInterpreterBytecodeArrayRegister, BYTECODE_ARRAY_TYPE, eax);
+  __ j(not_equal, &bytecode_array_not_present);
 
   // Push bytecode array.
   __ push(kInterpreterBytecodeArrayRegister);
   // Push zero for bytecode array offset.
   __ push(Immediate(0));
 
   // Allocate the local and temporary register file on the stack.
   {
     // Load frame size from the BytecodeArray object.
     __ mov(ebx, FieldOperand(kInterpreterBytecodeArrayRegister,
@@ skipping 45 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;
   __ mov(debug_info, FieldOperand(eax, SharedFunctionInfo::kDebugInfoOffset));
   __ mov(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);
+  __ pop(edx);  // Callee's new target.
+  __ pop(edi);  // Callee's JS function.
+  __ pop(esi);  // Callee's context.
+  __ leave();   // Leave the frame so we can tail call.
+  __ mov(ecx, FieldOperand(edi, JSFunction::kSharedFunctionInfoOffset));
+  __ mov(ecx, FieldOperand(ecx, SharedFunctionInfo::kCodeOffset));
+  __ lea(ecx, FieldOperand(ecx, Code::kHeaderSize));
+  __ mov(FieldOperand(edi, JSFunction::kCodeEntryOffset), ecx);
+  __ RecordWriteCodeEntryField(edi, ecx, ebx);
+  __ jmp(ecx);
 }
 
 
 void Builtins::Generate_InterpreterExitTrampoline(MacroAssembler* masm) {
   // The return value is in accumulator, which is already in eax.
 
   // Leave the frame (also dropping the register file).
   __ leave();
 
   // Drop receiver + arguments and return.
@@ skipping 2205 matching lines @@
   // And "return" to the OSR entry point of the function.
   __ ret(0);
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_IA32