Add Zone-based handle allocation interface and reduce use of Isolate-based interfaces.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
===================================================================
--- runtime/vm/flow_graph_allocator.cc	(revision 43075)
+++ runtime/vm/flow_graph_allocator.cc	(working copy)
@@ -540,7 +540,7 @@
   const intptr_t block_count = postorder_.length();
   ASSERT(postorder_.Last()->IsGraphEntry());
   BitVector* current_interference_set = NULL;
-  Isolate* isolate = flow_graph_.isolate();
+  Zone* zone = flow_graph_.zone();
   for (intptr_t i = 0; i < (block_count - 1); i++) {
     BlockEntryInstr* block = postorder_[i];
 
@@ -558,8 +558,8 @@
 
     BlockInfo* loop_header = block_info->loop_header();
     if ((loop_header != NULL) && (loop_header->last_block() == block)) {
-      current_interference_set = new(isolate) BitVector(
-          isolate, flow_graph_.max_virtual_register_number());
+      current_interference_set = new(zone) BitVector(
+          zone, flow_graph_.max_virtual_register_number());
       ASSERT(loop_header->backedge_interference() == NULL);
       // All values flowing into the loop header are live at the back-edge and
       // can interfere with phi moves.
@@ -2025,9 +2025,9 @@
 void ReachingDefs::AddPhi(PhiInstr* phi) {
   // TODO(johnmccutchan): Fix handling of PhiInstr with PairLocation.
   if (phi->reaching_defs() == NULL) {
-    Isolate* isolate = Isolate::Current();
-    phi->set_reaching_defs(new(isolate) BitVector(
-        isolate, flow_graph_.max_virtual_register_number()));
+    Zone* zone = Thread::Current()->zone();

[siva, 2015/01/23 19:29:26]

Zone* zone = flow_graph_.zone();
here?

[koda, 2015/01/23 21:09:42]

Done.

+    phi->set_reaching_defs(new(zone) BitVector(
+        zone, flow_graph_.max_virtual_register_number()));
 
     // Compute initial set reaching defs set.
     bool depends_on_phi = false;