Implement async* functions in VM

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
===================================================================
--- runtime/vm/flow_graph_builder.cc	(revision 43883)
+++ runtime/vm/flow_graph_builder.cc	(working copy)
@@ -1111,7 +1111,9 @@
 
   AddReturnExit(node->token_pos(), return_value);
 
-  if ((function.IsAsyncClosure() || function.IsSyncGenClosure()) &&
+  if ((function.IsAsyncClosure() ||
+      function.IsSyncGenClosure() ||
+      function.IsAsyncGenClosure()) &&
       (node->return_type() == ReturnNode::kContinuationTarget)) {
     JoinEntryInstr* const join = new(I) JoinEntryInstr(
         owner()->AllocateBlockId(), owner()->try_index());
@@ -1483,11 +1485,28 @@
 }
 
 
-void EffectGraphVisitor::BuildYieldJump(LocalVariable* old_context,
-                                        LocalVariable* iterator_param,
-                                        const intptr_t old_ctx_level,
-                                        JoinEntryInstr* target) {
+void EffectGraphVisitor::BuildAsyncYieldJump(LocalVariable* old_context,
+                                             const intptr_t old_ctx_level,

[Ivan Posva, 2015/02/23 08:23:36]

old_ctx_level is not used in this function. Why is it being passed?

[hausner, 2015/02/23 17:12:01]

Copy-paste error. I think I will need it though since I'll have to add most of
the implicit variables of an async method in async*.

+                                             JoinEntryInstr* target) {
   // Building a jump consists of the following actions:
+  // * Restore the old context from :await_cxt_var.
+  // * Append a Goto to the target's join.
+  ASSERT((old_context != NULL) && old_context->is_captured());
+
+  // Restore the saved continuation context, i.e. the context that was
+  // saved into :await_ctx_var before the closure suspended.
+  BuildRestoreContext(*old_context);
+
+  // Goto saved join.
+  Goto(target);
+}
+
+
+void EffectGraphVisitor::BuildSyncYieldJump(LocalVariable* old_context,
+                                            LocalVariable* iterator_param,
+                                            const intptr_t old_ctx_level,
+                                            JoinEntryInstr* target) {
+  // Building a jump consists of the following actions:
   // * Load the generator body's iterator parameter (:iterator)
   //   from the current context into a temporary.
   // * Restore the old context from :await_cxt_var.
@@ -3882,7 +3901,9 @@
   // The preamble is generated after visiting the body.
   GotoInstr* preamble_start = NULL;
   if (is_top_level_sequence &&
-      (function.IsAsyncClosure() || function.IsSyncGenClosure())) {
+      (function.IsAsyncClosure() ||
+          function.IsSyncGenClosure() ||
+          function.IsAsyncGenClosure())) {
     JoinEntryInstr* preamble_end = new(I) JoinEntryInstr(
         owner()->AllocateBlockId(), owner()->try_index());
     ASSERT(exit() != NULL);
@@ -3908,7 +3929,9 @@
   // After generating the CFG for the body we can create the preamble
   // because we know exactly how many continuation states we need.
   if (is_top_level_sequence &&
-      (function.IsAsyncClosure() || function.IsSyncGenClosure())) {
+      (function.IsAsyncClosure() ||
+          function.IsSyncGenClosure() ||
+          function.IsAsyncGenClosure())) {
     ASSERT(preamble_start != NULL);
     // We are at the top level. Fetch the corresponding scope.
     LocalScope* top_scope = node->scope();
@@ -3954,14 +3977,19 @@
                                 stack_trace_param,
                                 (*owner()->await_levels())[i],
                                 (*owner()->await_joins())[i]);
+      } else if (function.IsAsyncGenClosure()) {
+        for_true.BuildAsyncYieldJump(old_context,
+                                    (*owner()->await_levels())[i],
+                                    (*owner()->await_joins())[i]);
+
       } else {
         ASSERT(function.IsSyncGenClosure());
         LocalVariable* iterator_param =
             top_scope->LookupVariable(Symbols::IteratorParameter(), false);
-        for_true.BuildYieldJump(old_context,
-                                iterator_param,
-                                (*owner()->await_levels())[i],
-                                (*owner()->await_joins())[i]);
+        for_true.BuildSyncYieldJump(old_context,
+                                    iterator_param,
+                                    (*owner()->await_levels())[i],
+                                    (*owner()->await_joins())[i]);
       }
 
       Join(for_test, for_true, for_false);