Complete unrolling of loops with small body and trip count one.

Rationale:
Avoids the unnecessary loop control overhead, suspend check,
and exposes more opportunities for constant folding in the
resulting loop body. Fully unrolls loop in execute() of
the Dhrystone benchmark (3% to 8% improvements).

Test: test-art-host

Change-Id: If30f38caea9e9f87a929df041dfb7ed1c227aba3

1 files changed, 5 insertions, 3 deletions

diff --git a/compiler/optimizing/loop_optimization.h b/compiler/optimizing/loop_optimization.h
index 0f05b24c37..9ddab4150c 100644
--- a/compiler/optimizing/loop_optimization.h
+++ b/compiler/optimizing/loop_optimization.h
@@ -60,19 +60,21 @@ class HLoopOptimization : public HOptimization {
 
   void TraverseLoopsInnerToOuter(LoopNode* node);
 
+  // Simplification.
   void SimplifyInduction(LoopNode* node);
   void SimplifyBlocks(LoopNode* node);
-  void RemoveIfEmptyInnerLoop(LoopNode* node);
+  bool SimplifyInnerLoop(LoopNode* node);
 
+  // Helpers.
   bool IsPhiInduction(HPhi* phi);
   bool IsEmptyHeader(HBasicBlock* block);
   bool IsEmptyBody(HBasicBlock* block);
-
   bool IsOnlyUsedAfterLoop(HLoopInformation* loop_info,
                            HInstruction* instruction,
+                           bool collect_loop_uses,
                            /*out*/ int32_t* use_count);
-  void ReplaceAllUses(HInstruction* instruction, HInstruction* replacement);
   bool TryReplaceWithLastValue(HInstruction* instruction, HBasicBlock* block);
+  void RemoveDeadInstructions(const HInstructionList& list);
 
   // Range information based on prior induction variable analysis.
   InductionVarRange induction_range_;