ART: Implement loop full unrolling.

Performs whole loop unrolling for small loops with small
trip count to eliminate the loop check overhead, to have
more opportunities for inter-iteration optimizations.

caffeinemark/FloatAtom: 1.2x performance on arm64 Cortex-A57.

Test: 530-checker-peel-unroll.
Test: test-art-host, test-art-target.
Change-Id: Idf3fe3cb611376935d176c60db8c49907222e28a

1 files changed, 6 insertions, 0 deletions

diff --git a/compiler/optimizing/loop_optimization.h b/compiler/optimizing/loop_optimization.h
index bc4792458b..644b740ed4 100644
--- a/compiler/optimizing/loop_optimization.h
+++ b/compiler/optimizing/loop_optimization.h
@@ -155,6 +155,12 @@ class HLoopOptimization : public HOptimization {
   bool TryPeelingForLoopInvariantExitsElimination(LoopAnalysisInfo* analysis_info,
                                                   bool generate_code = true);
 
+  // Tries to perform whole loop unrolling for a small loop with a small trip count to eliminate
+  // the loop check overhead and to have more opportunities for inter-iteration optimizations.
+  // Returns whether transformation happened. 'generate_code' determines whether the optimization
+  // should be actually applied.
+  bool TryFullUnrolling(LoopAnalysisInfo* analysis_info, bool generate_code = true);
+
   // Tries to apply scalar loop peeling and unrolling.
   bool TryPeelingAndUnrolling(LoopNode* node);