Turn array index dehoisting into a proper HPhase.

src/hydrogen-dehoist.cc

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (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-dehoist.h"
+
+namespace v8 {
+namespace internal {
+
+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 (!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 (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));
+      }
+    }
+  }
+}
+
+} }  // namespace v8::internal