ART: Implement scalar loop unrolling.

Implement scalar loop unrolling for small loops
(on arm64) with known trip count to reduce loop check
and branch penalty and to provide more opportunities
for instruction scheduling.

Note: this functionality is turned off by default now.

Test: cloner_test.cc
Test: test-art-target, test-art-host

Change-Id: Ic27fd8fb0bc0d7b69251252da37b8b510bc30acc

1 files changed, 16 insertions, 2 deletions

diff --git a/compiler/optimizing/induction_var_range.h b/compiler/optimizing/induction_var_range.h
index 0b980f596a..906dc6bb7b 100644
--- a/compiler/optimizing/induction_var_range.h
+++ b/compiler/optimizing/induction_var_range.h
@@ -161,9 +161,15 @@ class InductionVarRange {
   }
 
   /**
-   * Checks if header logic of a loop terminates. Sets trip-count tc if known.
+   * Checks if header logic of a loop terminates. If trip count is known sets 'trip_count' to its
+   * value.
    */
-  bool IsFinite(HLoopInformation* loop, /*out*/ int64_t* tc) const;
+  bool IsFinite(HLoopInformation* loop, /*out*/ int64_t* trip_count) const;
+
+  /**
+   * Checks if a trip count is known for the loop and sets 'trip_count' to its value in this case.
+   */
+  bool HasKnownTripCount(HLoopInformation* loop, /*out*/ int64_t* trip_count) const;
 
   /**
    * Checks if the given instruction is a unit stride induction inside the closest enveloping
@@ -194,6 +200,14 @@ class InductionVarRange {
   };
 
   /**
+   * Checks if header logic of a loop terminates. If trip count is known (constant) sets
+   * 'is_constant' to true and 'trip_count' to the trip count value.
+   */
+  bool CheckForFiniteAndConstantProps(HLoopInformation* loop,
+                                      /*out*/ bool* is_constant,
+                                      /*out*/ int64_t* trip_count) const;
+
+  /**
    * Returns true if exact or upper/lower bound on the given induction
    * information is known as a 64-bit constant, which is returned in value.
    */