Fix context unchaining (issue 5991015).

runtime/vm/code_generator_x64.cc

 // Copyright (c) 2012, 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"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/code_generator.h"
 
 #include "lib/error.h"
@@ skipping 966 matching lines @@
   // code checking the type of the actual arguments.
   if (FLAG_enable_type_checks &&
       (node_sequence == parsed_function_.node_sequence())) {
     GenerateArgumentTypeChecks();
   }
   for (int i = 0; i < node_sequence->length(); i++) {
     AstNode* child_node = node_sequence->NodeAt(i);
     state()->set_root_node(child_node);
     child_node->Visit(this);
   }
-  if (node_sequence->label() != NULL) {
-    __ Bind(node_sequence->label()->break_label());
-  }
   if (num_context_variables > 0) {
     // Unchain the previously allocated context.
     __ movq(CTX, FieldAddress(CTX, Context::parent_offset()));
   }
+  // If this node sequence is labeled, a break out of the sequence will have
+  // taken care of unchaining the context.
+  if (node_sequence->label() != NULL) {
+    __ Bind(node_sequence->label()->break_label());
+  }
 }
 
 
 void CodeGenerator::VisitArgumentListNode(ArgumentListNode* arguments) {
   for (int i = 0; i < arguments->length(); i++) {
     AstNode* argument = arguments->NodeAt(i);
     argument->Visit(this);
   }
 }
 
@@ skipping 208 matching lines @@
 
 
 void CodeGenerator::VisitUnaryOpNode(UnaryOpNode* node) {
   if (node->kind() == Token::kNOT) {
     // "!" cannot be overloaded, therefore inline it.
     GenerateLogicalNotOp(node);
     return;
   }
   node->operand()->Visit(this);
   if (node->kind() == Token::kADD) {
+    // TODO(srdjan): Remove this as it is not part of Dart language any longer.
     // Unary operator '+' does not exist, it's a NOP, skip it.
     if (!IsResultNeeded(node)) {
       __ popq(RAX);
     }
     return;
   }
   MarkDeoptPoint(node->id(), node->token_index());
   String& operator_name = String::ZoneHandle();
   if (node->kind() == Token::kSUB) {
     operator_name = String::NewSymbol(Token::Str(Token::kNEGATE));
@@ skipping 750 matching lines @@
 
   // Generate inlined code for all finally blocks as we may transfer
   // control out of the 'try' blocks if any.
   for (intptr_t i = 0; i < node->inlined_finally_list_length(); i++) {
     node->InlinedFinallyNodeAt(i)->Visit(this);
   }
 
   // Unchain the context(s) up to the outer context level of the scope which
   // contains the destination label.
   ASSERT(label->owner() != NULL);
-  LocalScope* outer_context_owner = label->owner()->parent();
-  ASSERT(outer_context_owner != NULL);
   int target_context_level = 0;
-  if (outer_context_owner->HasContextLevel()) {
-    target_context_level = outer_context_owner->context_level();
-    ASSERT(target_context_level >= 0);
-    int context_level = state()->context_level();
-    ASSERT(context_level >= target_context_level);
-    while (context_level-- > target_context_level) {
-      __ movq(CTX, FieldAddress(CTX, Context::parent_offset()));
+  LocalScope* target_scope = label->owner();
+  if (target_scope->num_context_variables() > 0) {
+    // The scope of the target label allocates a context, therefore its outer
+    // scope is at a lower context level.
+    target_context_level = target_scope->context_level() - 1;
+  } else {
+    // The scope of the target label does not allocate a context, so its outer
+    // scope is at the same context level. Find it.
+    while ((target_scope != NULL) &&
+           (target_scope->num_context_variables() == 0)) {
+      target_scope = target_scope->parent();
     }
+    if (target_scope != NULL) {
+      target_context_level = target_scope->context_level();
+    }
+  }
+  ASSERT(target_context_level >= 0);
+  int context_level = state()->context_level();
+  ASSERT(context_level >= target_context_level);
+  while (context_level-- > target_context_level) {
+    __ movq(CTX, FieldAddress(CTX, Context::parent_offset()));
   }
 
   if (node->kind() == Token::kBREAK) {
     __ jmp(label->break_label());
   } else {
     __ jmp(label->continue_label());
   }
 }
 
 
@@ skipping 778 matching lines @@
   const Error& error = Error::Handle(
       Parser::FormatError(script, token_index, "Error", format, args));
   va_end(args);
   Isolate::Current()->long_jump_base()->Jump(1, error);
   UNREACHABLE();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64