Subzero: Pull the node name out of the node structure.

Instead, non-empty node names are kept in a single vector in the Cfg
object.

This is toward the goal of pulling non-POD fields out of the CfgNode
class so that CfgNode can be arena-allocated and not leak memory.

Also, actual setting of the node name is now guarded by ALLOW_DUMP.

BUG= none
R=jvoung@chromium.org, kschimpf@google.com

Review URL: https://codereview.chromium.org/787333005

src/IceConverter.cpp

diff --git a/src/IceConverter.cpp b/src/IceConverter.cpp
index e06e290..a8148f9 100644
--- a/src/IceConverter.cpp
+++ b/src/IceConverter.cpp
@@ -156,7 +156,9 @@
 
   Ice::CfgNode *mapBasicBlockToNode(const BasicBlock *BB) {
     if (NodeMap.find(BB) == NodeMap.end()) {
-      NodeMap[BB] = Func->makeNode(BB->getName());
+      NodeMap[BB] = Func->makeNode();
+      if (ALLOW_DUMP)
+        NodeMap[BB]->setName(BB->getName());
     }
     return NodeMap[BB];
   }