Revert my last change r11227.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 11228)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -955,45 +955,29 @@
 }
 
 
-void DominatorBasedCSE::Optimize(BlockEntryInstr* graph_entry) {
-  ASSERT(graph_entry->IsGraphEntry());
-  DirectChainedHashMap<BindInstr*> map;
-  OptimizeRecursive(graph_entry, &map);
-}
-
-
-void DominatorBasedCSE::OptimizeRecursive(
-    BlockEntryInstr* block,
-    DirectChainedHashMap<BindInstr*>* map) {
-  for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
-    BindInstr* instr = it.Current()->AsBind();
-    if (instr == NULL || instr->computation()->HasSideEffect()) continue;
-    BindInstr* result = map->Lookup(instr);
-    if (result == NULL) {
-      map->Insert(instr);
-      continue;
+void LocalCSE::Optimize() {
+  for (intptr_t i = 0; i < blocks_.length(); ++i) {
+    BlockEntryInstr* entry = blocks_[i];
+    DirectChainedHashMap<BindInstr*> map;
+    ASSERT(map.IsEmpty());
+    for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
+      BindInstr* instr = it.Current()->AsBind();
+      if (instr == NULL || instr->computation()->HasSideEffect()) continue;
+      BindInstr* result = map.Lookup(instr);
+      if (result == NULL) {
+        map.Insert(instr);
+        continue;
+      }
+      // Replace current with lookup result.
+      instr->ReplaceUsesWith(result);
+      it.RemoveCurrentFromGraph();
+      if (FLAG_trace_optimization) {
+        OS::Print("Replacing v%d with v%d\n",
+                  instr->ssa_temp_index(),
+                  result->ssa_temp_index());
+      }
     }
-    // Replace current with lookup result.
-    instr->ReplaceUsesWith(result);
-    it.RemoveCurrentFromGraph();
-    if (FLAG_trace_optimization) {
-      OS::Print("Replacing v%d with v%d\n",
-                instr->ssa_temp_index(),
-                result->ssa_temp_index());
-    }
   }
-
-  // Process children in the dominator tree recursively.
-  intptr_t num_children = block->dominated_blocks().length();
-  for (intptr_t i = 0; i < num_children; ++i) {
-    BlockEntryInstr* child = block->dominated_blocks()[i];
-    if (i < num_children - 1) {
-      DirectChainedHashMap<BindInstr*> child_map(*map);  // Copy map.
-      OptimizeRecursive(child, &child_map);
-    } else {
-      OptimizeRecursive(child, map);  // Reuse map for the last child.
-    }
-  }
 }