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, 21 insertions, 7 deletions

diff --git a/compiler/optimizing/induction_var_range.cc b/compiler/optimizing/induction_var_range.cc
index 0a310ca940..55eca2316a 100644
--- a/compiler/optimizing/induction_var_range.cc
+++ b/compiler/optimizing/induction_var_range.cc
@@ -352,13 +352,15 @@ void InductionVarRange::Replace(HInstruction* instruction,
 }
 
 bool InductionVarRange::IsFinite(HLoopInformation* loop, /*out*/ int64_t* trip_count) const {
-  HInductionVarAnalysis::InductionInfo *trip =
-      induction_analysis_->LookupInfo(loop, GetLoopControl(loop));
-  if (trip != nullptr && !IsUnsafeTripCount(trip)) {
-    IsConstant(trip->op_a, kExact, trip_count);
-    return true;
-  }
-  return false;
+  bool is_constant_unused = false;
+  return CheckForFiniteAndConstantProps(loop, &is_constant_unused, trip_count);
+}
+
+bool InductionVarRange::HasKnownTripCount(HLoopInformation* loop,
+                                          /*out*/ int64_t* trip_count) const {
+  bool is_constant = false;
+  CheckForFiniteAndConstantProps(loop, &is_constant, trip_count);
+  return is_constant;
 }
 
 bool InductionVarRange::IsUnitStride(HInstruction* context,
@@ -417,6 +419,18 @@ HInstruction* InductionVarRange::GenerateTripCount(HLoopInformation* loop,
 // Private class methods.
 //
 
+bool InductionVarRange::CheckForFiniteAndConstantProps(HLoopInformation* loop,
+                                                       /*out*/ bool* is_constant,
+                                                       /*out*/ int64_t* trip_count) const {
+  HInductionVarAnalysis::InductionInfo *trip =
+      induction_analysis_->LookupInfo(loop, GetLoopControl(loop));
+  if (trip != nullptr && !IsUnsafeTripCount(trip)) {
+    *is_constant = IsConstant(trip->op_a, kExact, trip_count);
+    return true;
+  }
+  return false;
+}
+
 bool InductionVarRange::IsConstant(HInductionVarAnalysis::InductionInfo* info,
                                    ConstantRequest request,
                                    /*out*/ int64_t* value) const {