Synchronize with r15701.

src/hydrogen-dehoist.cc

Index: src/hydrogen-dehoist.cc
diff --git a/src/hydrogen-redundant-phi.cc b/src/hydrogen-dehoist.cc
similarity index 51%
copy from src/hydrogen-redundant-phi.cc
copy to src/hydrogen-dehoist.cc
index 9c38200577d4994e79f5e1925039ca10a8c8a8c2..696d22c608e5b707635b13229cf0046dda4c3e03 100644
--- a/src/hydrogen-redundant-phi.cc
+++ b/src/hydrogen-dehoist.cc
@@ -25,52 +25,56 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#include "hydrogen-redundant-phi.h"
+#include "hydrogen-dehoist.h"
 
 namespace v8 {
 namespace internal {
 
-void HRedundantPhiEliminationPhase::Run() {
-  // We do a simple fixed point iteration without any work list, because
-  // machine-generated JavaScript can lead to a very dense Hydrogen graph with
-  // an enormous work list and will consequently result in OOM. Experiments
-  // showed that this simple algorithm is good enough, and even e.g. tracking
-  // the set or range of blocks to consider is not a real improvement.
-  bool need_another_iteration;
-  const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
-  ZoneList<HPhi*> redundant_phis(blocks->length(), zone());
-  do {
-    need_another_iteration = false;
-    for (int i = 0; i < blocks->length(); ++i) {
-      HBasicBlock* block = blocks->at(i);
-      for (int j = 0; j < block->phis()->length(); j++) {
-        HPhi* phi = block->phis()->at(j);
-        HValue* replacement = phi->GetRedundantReplacement();
-        if (replacement != NULL) {
-          // Remember phi to avoid concurrent modification of the block's phis.
-          redundant_phis.Add(phi, zone());
-          for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
-            HValue* value = it.value();
-            value->SetOperandAt(it.index(), replacement);
-            need_another_iteration |= value->IsPhi();
-          }
-        }
-      }
-      for (int i = 0; i < redundant_phis.length(); i++) {
-        block->RemovePhi(redundant_phis[i]);
-      }
-      redundant_phis.Clear();
-    }
-  } while (need_another_iteration);
+static void DehoistArrayIndex(ArrayInstructionInterface* array_operation) {
+  HValue* index = array_operation->GetKey()->ActualValue();
+  if (!index->representation().IsSmiOrInteger32()) return;
+  if (!index->IsAdd() && !index->IsSub()) return;
+
+  HConstant* constant;
+  HValue* subexpression;
+  HBinaryOperation* binary_operation = HBinaryOperation::cast(index);
+  if (binary_operation->left()->IsConstant()) {
+    subexpression = binary_operation->right();
+    constant = HConstant::cast(binary_operation->left());
+  } else if (binary_operation->right()->IsConstant()) {
+    subexpression = binary_operation->left();
+    constant = HConstant::cast(binary_operation->right());
+  } else {
+    return;
+  }
 
-#if DEBUG
-  // Make sure that we *really* removed all redundant phis.
+  if (!constant->HasInteger32Value()) return;
+  int32_t sign = binary_operation->IsSub() ? -1 : 1;
+  int32_t value = constant->Integer32Value() * sign;
+  // We limit offset values to 30 bits because we want to avoid the risk of
+  // overflows when the offset is added to the object header size.
+  if (value >= 1 << 30 || value < 0) return;
+  array_operation->SetKey(subexpression);
+  if (binary_operation->HasNoUses()) {
+    binary_operation->DeleteAndReplaceWith(NULL);
+  }
+  array_operation->SetIndexOffset(static_cast<uint32_t>(value));
+  array_operation->SetDehoisted(true);
+}
+
+
+void HDehoistIndexComputationsPhase::Run() {
+  const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
   for (int i = 0; i < blocks->length(); ++i) {
-    for (int j = 0; j < blocks->at(i)->phis()->length(); j++) {
-      ASSERT(blocks->at(i)->phis()->at(j)->GetRedundantReplacement() == NULL);
+    for (HInstructionIterator it(blocks->at(i)); !it.Done(); it.Advance()) {
+      HInstruction* instr = it.Current();
+      if (instr->IsLoadKeyed()) {
+        DehoistArrayIndex(HLoadKeyed::cast(instr));
+      } else if (instr->IsStoreKeyed()) {
+        DehoistArrayIndex(HStoreKeyed::cast(instr));
+      }
     }
   }
-#endif
 }
 
 } }  // namespace v8::internal