Turn merge removable simulates into a proper HPhase.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 1b113305ef14714e6ad984ef73fea859c405d2ce..096c4e3356a9548c99bac1bed77a9460cbdbd110 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -44,6 +44,7 @@
 #include "hydrogen-osr.h"
 #include "hydrogen-range-analysis.h"
 #include "hydrogen-redundant-phi.h"
+#include "hydrogen-removable-simulates.h"
 #include "hydrogen-representation-changes.h"
 #include "hydrogen-sce.h"
 #include "hydrogen-uint32-analysis.h"
@@ -2572,69 +2573,6 @@ void HGraph::CollectPhis() {
 }
 
 
-void HGraph::MergeRemovableSimulates() {
-  HPhase phase("H_Merge removable simulates", this);
-  ZoneList<HSimulate*> mergelist(2, zone());
-  for (int i = 0; i < blocks()->length(); ++i) {
-    HBasicBlock* block = blocks()->at(i);
-    // Make sure the merge list is empty at the start of a block.
-    ASSERT(mergelist.is_empty());
-    // Nasty heuristic: Never remove the first simulate in a block. This
-    // just so happens to have a beneficial effect on register allocation.
-    bool first = true;
-    for (HInstructionIterator it(block); !it.Done(); it.Advance()) {
-      HInstruction* current = it.Current();
-      if (current->IsLeaveInlined()) {
-        // Never fold simulates from inlined environments into simulates
-        // in the outer environment.
-        // (Before each HEnterInlined, there is a non-foldable HSimulate
-        // anyway, so we get the barrier in the other direction for free.)
-        // Simply remove all accumulated simulates without merging.  This
-        // is safe because simulates after instructions with side effects
-        // are never added to the merge list.
-        while (!mergelist.is_empty()) {
-          mergelist.RemoveLast()->DeleteAndReplaceWith(NULL);
-        }
-        continue;
-      }
-      if (current->IsReturn()) {
-        // Drop mergeable simulates in the list. This is safe because
-        // simulates after instructions with side effects are never added
-        // to the merge list.
-        while (!mergelist.is_empty()) {
-          mergelist.RemoveLast()->DeleteAndReplaceWith(NULL);
-        }
-        continue;
-      }
-      // Skip the non-simulates and the first simulate.
-      if (!current->IsSimulate()) continue;
-      if (first) {
-        first = false;
-        continue;
-      }
-      HSimulate* current_simulate = HSimulate::cast(current);
-      if ((current_simulate->previous()->HasObservableSideEffects() &&
-           !current_simulate->next()->IsSimulate()) ||
-          !current_simulate->is_candidate_for_removal()) {
-        // This simulate is not suitable for folding.
-        // Fold the ones accumulated so far.
-        current_simulate->MergeWith(&mergelist);
-        continue;
-      } else {
-        // Accumulate this simulate for folding later on.
-        mergelist.Add(current_simulate, zone());
-      }
-    }
-
-    if (!mergelist.is_empty()) {
-      // Merge the accumulated simulates at the end of the block.
-      HSimulate* last = mergelist.RemoveLast();
-      last->MergeWith(&mergelist);
-    }
-  }
-}
-
-
 void HGraph::RecursivelyMarkPhiDeoptimizeOnUndefined(HPhi* phi) {
   if (!phi->CheckFlag(HValue::kAllowUndefinedAsNaN)) return;
   phi->ClearFlag(HValue::kAllowUndefinedAsNaN);
@@ -3137,7 +3075,7 @@ bool HGraph::Optimize(SmartArrayPointer<char>* bailout_reason) {
   // Remove HSimulate instructions that have turned out not to be needed
   // after all by folding them into the following HSimulate.
   // This must happen after inferring representations.
-  MergeRemovableSimulates();
+  Run<HMergeRemovableSimulatesPhase>();
 
   MarkDeoptimizeOnUndefined();
   Run<HRepresentationChangesPhase>();