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+/*
+ * Copyright (C) 2018 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_OPTIMIZING_LOOP_ANALYSIS_H_
+#define ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_
+
+#include "nodes.h"
+
+namespace art {
+
+class LoopAnalysis;
+
+// No loop unrolling factor (just one copy of the loop-body).
+static constexpr uint32_t kNoUnrollingFactor = 1;
+
+// Class to hold cached information on properties of the loop.
+class LoopAnalysisInfo : public ValueObject {
+ public:
+  explicit LoopAnalysisInfo(HLoopInformation* loop_info)
+      : bb_num_(0),
+        instr_num_(0),
+        exits_num_(0),
+        has_instructions_preventing_scalar_unrolling_(false),
+        loop_info_(loop_info) {}
+
+  size_t GetNumberOfBasicBlocks() const { return bb_num_; }
+  size_t GetNumberOfInstructions() const { return instr_num_; }
+  size_t GetNumberOfExits() const { return exits_num_; }
+
+  bool HasInstructionsPreventingScalarUnrolling() const {
+    return has_instructions_preventing_scalar_unrolling_;
+  }
+
+  const HLoopInformation* GetLoopInfo() const { return loop_info_; }
+
+ private:
+  // Number of basic blocks in the loop body.
+  size_t bb_num_;
+  // Number of instructions in the loop body.
+  size_t instr_num_;
+  // Number of loop's exits.
+  size_t exits_num_;
+  // Whether the loop has instructions which make scalar loop unrolling non-beneficial.
+  bool has_instructions_preventing_scalar_unrolling_;
+
+  // Corresponding HLoopInformation.
+  const HLoopInformation* loop_info_;
+
+  friend class LoopAnalysis;
+};
+
+// Placeholder class for methods and routines used to analyse loops, calculate loop properties
+// and characteristics.
+class LoopAnalysis : public ValueObject {
+ public:
+  // Calculates loops basic properties like body size, exits number, etc. and fills
+  // 'analysis_results' with this information.
+  static void CalculateLoopBasicProperties(HLoopInformation* loop_info,
+                                           LoopAnalysisInfo* analysis_results);
+
+ private:
+  // Returns whether an instruction makes scalar loop unrolling non-beneficial.
+  //
+  // If in the loop body we have a dex/runtime call then its contribution to the whole
+  // loop performance will probably prevail. So unrolling optimization will not bring
+  // any noticeable performance improvement however will increase the code size.
+  static bool MakesScalarUnrollingNonBeneficial(HInstruction* instruction) {
+    return (instruction->IsNewArray() ||
+        instruction->IsNewInstance() ||
+        instruction->IsUnresolvedInstanceFieldGet() ||
+        instruction->IsUnresolvedInstanceFieldSet() ||
+        instruction->IsUnresolvedStaticFieldGet() ||
+        instruction->IsUnresolvedStaticFieldSet() ||
+        // TODO: Unroll loops with intrinsified invokes.
+        instruction->IsInvoke() ||
+        // TODO: Unroll loops with ClinitChecks.
+        instruction->IsClinitCheck());
+  }
+};
+
+//
+// Helper class which holds target-dependent methods and constants needed for loop optimizations.
+//
+// To support peeling/unrolling for a new architecture one needs to create new helper class,
+// inherit it from this and add implementation for the following methods.
+//
+class ArchDefaultLoopHelper : public ArenaObject<kArenaAllocOptimization> {
+ public:
+  virtual ~ArchDefaultLoopHelper() {}
+
+  // Creates an instance of specialised helper for the target or default helper if the target
+  // doesn't support loop peeling and unrolling.
+  static ArchDefaultLoopHelper* Create(InstructionSet isa, ArenaAllocator* allocator);
+
+  // Returns whether the loop is too big for loop unrolling by checking its total number of
+  // basic blocks and instructions.
+  //
+  // If the loop body has too many instructions then unrolling optimization will not bring
+  // any noticeable performance improvement however will increase the code size.
+  //
+  // Returns 'true' by default, should be overridden by particular target loop helper.
+  virtual bool IsLoopTooBigForScalarUnrolling(
+      LoopAnalysisInfo* loop_analysis_info ATTRIBUTE_UNUSED) const { return true; }
+
+  // Returns optimal scalar unrolling factor for the loop.
+  //
+  // Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
+  virtual uint32_t GetScalarUnrollingFactor(HLoopInformation* loop_info ATTRIBUTE_UNUSED,
+                                            uint64_t trip_count ATTRIBUTE_UNUSED) const {
+    return kNoUnrollingFactor;
+  }
+
+  // Returns optimal SIMD unrolling factor for the loop.
+  //
+  // Returns kNoUnrollingFactor by default, should be overridden by particular target loop helper.
+  virtual uint32_t GetSIMDUnrollingFactor(HBasicBlock* block ATTRIBUTE_UNUSED,
+                                          int64_t trip_count ATTRIBUTE_UNUSED,
+                                          uint32_t max_peel ATTRIBUTE_UNUSED,
+                                          uint32_t vector_length ATTRIBUTE_UNUSED) const {
+    return kNoUnrollingFactor;
+  }
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_LOOP_ANALYSIS_H_