Refactor handling of input records.

Introduce HInstruction::GetInputRecords(), a new virtual
function that returns an ArrayRef<> to all input records.
Implement all other functions dealing with input records as
wrappers around GetInputRecords(). Rewrite functions that
previously used multiple virtual calls to deal with input
records, especially in loops, to prefetch the ArrayRef<>
only once for each instruction.  Besides avoiding all the
extra calls, this also allows the compiler (clang++) to
perform additional optimizations.

This speeds up the Nexus 5 boot image compilation by ~0.5s
(4% of "Compile Dex File", 2% of dex2oat time) on AOSP ToT.

Change-Id: Id8ebe0fb9405e38d918972a11bd724146e4ca578
diff --git a/compiler/utils/transform_array_ref.h b/compiler/utils/transform_array_ref.h
new file mode 100644
index 0000000..6297b88
--- /dev/null
+++ b/compiler/utils/transform_array_ref.h
@@ -0,0 +1,188 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_UTILS_TRANSFORM_ARRAY_REF_H_
+#define ART_COMPILER_UTILS_TRANSFORM_ARRAY_REF_H_
+
+#include <type_traits>
+
+#include "utils/array_ref.h"
+#include "utils/transform_iterator.h"
+
+namespace art {
+
+/**
+ * @brief An ArrayRef<> wrapper that uses a transformation function for element access.
+ */
+template <typename BaseType, typename Function>
+class TransformArrayRef {
+ private:
+  using Iter = TransformIterator<typename ArrayRef<BaseType>::iterator, Function>;
+
+  // The Function may take a non-const reference, so const_iterator may not exist.
+  using FallbackConstIter = std::iterator<std::random_access_iterator_tag, void, void, void, void>;
+  using PreferredConstIter =
+      TransformIterator<typename ArrayRef<BaseType>::const_iterator, Function>;
+  template <typename F, typename = typename std::result_of<F(const BaseType&)>::type>
+  static PreferredConstIter ConstIterHelper(int&);
+  template <typename F>
+  static FallbackConstIter ConstIterHelper(const int&);
+
+  using ConstIter = decltype(ConstIterHelper<Function>(*reinterpret_cast<int*>(0)));
+
+ public:
+  using value_type = typename Iter::value_type;
+  using reference = typename Iter::reference;
+  using const_reference = typename ConstIter::reference;
+  using pointer = typename Iter::pointer;
+  using const_pointer = typename ConstIter::pointer;
+  using iterator = Iter;
+  using const_iterator = typename std::conditional<
+      std::is_same<ConstIter, FallbackConstIter>::value,
+      void,
+      ConstIter>::type;
+  using reverse_iterator = std::reverse_iterator<Iter>;
+  using const_reverse_iterator = typename std::conditional<
+      std::is_same<ConstIter, FallbackConstIter>::value,
+      void,
+      std::reverse_iterator<ConstIter>>::type;
+  using difference_type = typename ArrayRef<BaseType>::difference_type;
+  using size_type = typename ArrayRef<BaseType>::size_type;
+
+  // Constructors.
+
+  TransformArrayRef(const TransformArrayRef& other) = default;
+
+  template <typename OtherBT>
+  TransformArrayRef(const ArrayRef<OtherBT>& base, Function fn)
+      : data_(base, fn) { }
+
+  // Assignment operators.
+
+  TransformArrayRef& operator=(const TransformArrayRef& other) = default;
+
+  template <typename OtherBT,
+            typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
+  TransformArrayRef& operator=(const TransformArrayRef<OtherBT, Function>& other) {
+    return *this = TransformArrayRef(other.base(), other.GetFunction());
+  }
+
+  // Destructor.
+  ~TransformArrayRef() = default;
+
+  // Iterators.
+  iterator begin() { return MakeIterator(base().begin()); }
+  const_iterator begin() const { return MakeIterator(base().cbegin()); }
+  const_iterator cbegin() const { return MakeIterator(base().cbegin()); }
+  iterator end() { return MakeIterator(base().end()); }
+  const_iterator end() const { MakeIterator(base().cend()); }
+  const_iterator cend() const { return MakeIterator(base().cend()); }
+  reverse_iterator rbegin() { return reverse_iterator(end()); }
+  const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
+  const_reverse_iterator crbegin() const { return const_reverse_iterator(cend()); }
+  reverse_iterator rend() { return reverse_iterator(begin()); }
+  const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
+  const_reverse_iterator crend() const { return const_reverse_iterator(cbegin()); }
+
+  // Size.
+  size_type size() const { return base().size(); }
+  bool empty() const { return base().empty(); }
+
+  // Element access. NOTE: Not providing data().
+
+  reference operator[](size_type n) { return GetFunction()(base()[n]); }
+  const_reference operator[](size_type n) const { return GetFunction()(base()[n]); }
+
+  reference front() { return GetFunction()(base().front()); }
+  const_reference front() const { return GetFunction()(base().front()); }
+
+  reference back() { return GetFunction()(base().back()); }
+  const_reference back() const { return GetFunction()(base().back()); }
+
+  TransformArrayRef SubArray(size_type pos) {
+    return TransformArrayRef(base().subarray(pos), GetFunction());
+  }
+  TransformArrayRef SubArray(size_type pos) const {
+    return TransformArrayRef(base().subarray(pos), GetFunction());
+  }
+  TransformArrayRef SubArray(size_type pos, size_type length) const {
+    return TransformArrayRef(base().subarray(pos, length), GetFunction());
+  }
+
+  // Retrieve the base ArrayRef<>.
+  ArrayRef<BaseType> base() {
+    return data_.base_;
+  }
+  ArrayRef<const BaseType> base() const {
+    return ArrayRef<const BaseType>(data_.base_);
+  }
+
+ private:
+  // Allow EBO for state-less Function.
+  struct Data : Function {
+   public:
+    Data(ArrayRef<BaseType> base, Function fn) : Function(fn), base_(base) { }
+
+    ArrayRef<BaseType> base_;
+  };
+
+  const Function& GetFunction() const {
+    return static_cast<const Function&>(data_);
+  }
+
+  template <typename BaseIterator>
+  auto MakeIterator(BaseIterator base) const {
+    return MakeTransformIterator(base, GetFunction());
+  }
+
+  Data data_;
+};
+
+template <typename BaseType, typename Function>
+bool operator==(const TransformArrayRef<BaseType, Function>& lhs,
+                const TransformArrayRef<BaseType, Function>& rhs) {
+  return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
+}
+
+template <typename BaseType, typename Function>
+bool operator!=(const TransformArrayRef<BaseType, Function>& lhs,
+                const TransformArrayRef<BaseType, Function>& rhs) {
+  return !(lhs == rhs);
+}
+
+template <typename ValueType, typename Function>
+TransformArrayRef<ValueType, Function> MakeTransformArrayRef(
+    ArrayRef<ValueType> container, Function f) {
+  return TransformArrayRef<ValueType, Function>(container, f);
+}
+
+template <typename Container, typename Function>
+TransformArrayRef<typename Container::value_type, Function> MakeTransformArrayRef(
+    Container& container, Function f) {
+  return TransformArrayRef<typename Container::value_type, Function>(
+      ArrayRef<typename Container::value_type>(container.data(), container.size()), f);
+}
+
+template <typename Container, typename Function>
+TransformArrayRef<const typename Container::value_type, Function> MakeTransformArrayRef(
+    const Container& container, Function f) {
+  return TransformArrayRef<const typename Container::value_type, Function>(
+      ArrayRef<const typename Container::value_type>(container.data(), container.size()), f);
+}
+
+}  // namespace art
+
+#endif  // ART_COMPILER_UTILS_TRANSFORM_ARRAY_REF_H_