Fix for issues 6080 - pass in the Isolate's top context into the stub for invoking dart code from n…

runtime/vm/stub_code_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/compiler.h"
@@ skipping 717 matching lines @@
   // done. The assumption is that this register will never be clobbered by
   // compiled or runtime stub code.
 
   // Cache the new Context pointer into CTX while executing Dart code.
   __ movq(CTX, Address(RCX, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load Isolate pointer from Context structure into R8.
   __ movq(R8, FieldAddress(CTX, Context::isolate_offset()));
 
   // Save the top exit frame info. Use RAX as a temporary register.
+  // StackFrameIterator reads the top exit frame info saved in this frame.
+  // The constant kExitLinkOffsetInEntryFrame must be kept in sync with the
+  // code below: kExitLinkOffsetInEntryFrame = -8 * kWordSize.
   __ movq(RAX, Address(R8, Isolate::top_exit_frame_info_offset()));
   __ pushq(RAX);
   __ movq(Address(R8, Isolate::top_exit_frame_info_offset()), Immediate(0));
 
-  // StackFrameIterator reads the top exit frame info saved in this frame.
-  // The constant kExitLinkOffsetInEntryFrame must be kept in sync with the
-  // code above: kExitLinkOffsetInEntryFrame = -8 * kWordSize.
-
   // Save the old Context pointer. Use RAX as a temporary register.
   // Note that VisitObjectPointers will find this saved Context pointer during
   // GC marking, since it traverses any information between SP and
   // FP - kExitLinkOffsetInEntryFrame.
+  // EntryFrame::SavedContext reads the context saved in this frame.
+  // The constant kSavedContextOffsetInEntryFrame must be kept in sync with
+  // the code below: kSavedContextOffsetInEntryFrame = -9 * kWordSize.
   __ movq(RAX, Address(R8, Isolate::top_context_offset()));
   __ pushq(RAX);
 
   // Load arguments descriptor array into R10, which is passed to Dart code.
   __ movq(R10, Address(RSI, VMHandles::kOffsetOfRawPtrInHandle));
 
   // Load number of arguments into RBX.
   __ movq(RBX, FieldAddress(R10, ArgumentsDescriptor::count_offset()));
   __ SmiUntag(RBX);
 
@@ skipping 491 matching lines @@
       tags = RawObject::ClassIdTag::update(context_class.id(), tags);
       __ movq(Address(RBX, Context::tags_offset()), Immediate(tags));
 
       // Set number of variables field to 1 (for captured receiver).
       __ movq(Address(RBX, Context::num_variables_offset()), Immediate(1));
 
       // Set isolate field to isolate of current context.
       __ movq(R10, FieldAddress(CTX, Context::isolate_offset()));
       __ movq(Address(RBX, Context::isolate_offset()), R10);
 
-      // Set the parent field to null.
+      // Set the parent to null.
       __ movq(Address(RBX, Context::parent_offset()), raw_null);
 
       // Initialize the context variable to the receiver.
       __ movq(R10, Address(RSP, kReceiverOffset));
       __ movq(Address(RBX, Context::variable_offset(0)), R10);
 
       // Set the newly allocated context in the newly allocated closure.
       __ addq(RBX, Immediate(kHeapObjectTag));
       __ movq(Address(RAX, Closure::context_offset()), RBX);
     } else {
@@ skipping 804 matching lines @@
   __ cmpq(left, right);
   __ Bind(&done);
   __ popq(right);
   __ popq(left);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64