Fix LookupCode for the DatePrototype_GetField builtin

src/builtins/mips/builtins-mips.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_MIPS
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 1838 matching lines @@
   __ Ret();
 
   // 3. Raise a TypeError if the receiver is not a date.
   __ bind(&receiver_not_date);
   {
     FrameScope scope(masm, StackFrame::MANUAL);
     __ Push(a0);
     __ Move(a0, Smi::FromInt(0));
     __ EnterBuiltinFrame(cp, a1, a0);
     __ CallRuntime(Runtime::kThrowNotDateError);
+
+    // It's far from obvious, but this final trailing instruction after the call
+    // is required for StackFrame::LookupCode to work correctly. To illustrate
+    // why: if call were the final instruction in the code object, then the pc
+    // (== return address) would point beyond the code object when the stack is
+    // traversed. When we then try to look up the code object through
+    // StackFrame::LookupCode, we actually return the next code object that
+    // happens to be on the same page in memory.
+    // TODO(jgruber): A proper fix for this would be nice.
+    __ nop();
   }
 }
 
 // static
 void Builtins::Generate_FunctionPrototypeApply(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- a0    : argc
   //  -- sp[0] : argArray
   //  -- sp[4] : thisArg
   //  -- sp[8] : receiver
@@ skipping 1136 matching lines @@
     __ break_(0xCC);
   }
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS