Fix deoptimization of context.

src/deoptimizer.cc

 // Copyright 2013 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/disasm.h"
@@ skipping 1049 matching lines @@
   // so long as we don't inline functions that need local contexts.
   Register context_reg = JavaScriptFrame::context_register();
   output_offset -= kPointerSize;
   input_offset -= kPointerSize;
   // Read the context from the translations.
   DoTranslateCommand(iterator, frame_index, output_offset);
   value = output_frame->GetFrameSlot(output_offset);
   // The context should not be a placeholder for a materialized object.
   CHECK(value !=
         reinterpret_cast<intptr_t>(isolate_->heap()->arguments_marker()));
+  if (value ==
+      reinterpret_cast<intptr_t>(isolate_->heap()->undefined_value())) {
+    // If the context was optimized away, just use the context from
+    // the activation. This should only apply to Crankshaft code.
+    CHECK(!compiled_code_->is_turbofanned());
+    if (is_bottommost) {
+      value = input_->GetFrameSlot(input_offset);
+    } else {
+      value = reinterpret_cast<intptr_t>(function->context());
+    }
+    output_frame->SetFrameSlot(output_offset, value);
+  }
   output_frame->SetContext(value);
   if (is_topmost) output_frame->SetRegister(context_reg.code(), value);
   if (trace_scope_ != NULL) {
     PrintF(trace_scope_->file(),
            "    0x%08" V8PRIxPTR ": [top + %d] <- 0x%08"
            V8PRIxPTR "; context\n",
            top_address + output_offset, output_offset, value);
   }
 
   // The function was mentioned explicitly in the BEGIN_FRAME.
@@ skipping 2583 matching lines @@
 
 
 void DeoptimizedFrameInfo::Iterate(ObjectVisitor* v) {
   v->VisitPointer(BitCast<Object**>(&function_));
   v->VisitPointer(&context_);
   v->VisitPointers(parameters_, parameters_ + parameters_count_);
   v->VisitPointers(expression_stack_, expression_stack_ + expression_count_);
 }
 
 } }  // namespace v8::internal