Recognize XOR-based periodic induction.

Rationale:
This is a commonly used construct (e.g. x = !x for booleans
and x ^= 1 for integers). This CL prepares some upcoming
optimizations that exploit such inductions.

Change-Id: I46edffb9de1075a836995daf5c2dfff7891f3034
Test: 530-checker-loops2 and induction_var_analysis_test

1 files changed, 17 insertions, 0 deletions

diff --git a/compiler/optimizing/induction_var_range.cc b/compiler/optimizing/induction_var_range.cc
index cd8b7c7960..140c7f0c40 100644
--- a/compiler/optimizing/induction_var_range.cc
+++ b/compiler/optimizing/induction_var_range.cc
@@ -525,6 +525,8 @@ InductionVarRange::Value InductionVarRange::GetVal(HInductionVarAnalysis::Induct
             return GetMul(info->op_a, info->op_b, trip, in_body, is_min);
           case HInductionVarAnalysis::kDiv:
             return GetDiv(info->op_a, info->op_b, trip, in_body, is_min);
+          case HInductionVarAnalysis::kXor:
+            return GetXor(info->op_a, info->op_b);
           case HInductionVarAnalysis::kFetch:
             return GetFetch(info->fetch, trip, in_body, is_min);
           case HInductionVarAnalysis::kTripCountInLoop:
@@ -626,6 +628,21 @@ InductionVarRange::Value InductionVarRange::GetDiv(HInductionVarAnalysis::Induct
   return Value();
 }
 
+InductionVarRange::Value InductionVarRange::GetXor(
+    HInductionVarAnalysis::InductionInfo* info1,
+    HInductionVarAnalysis::InductionInfo* info2) const {
+  int64_t v1 = 0;
+  int64_t v2 = 0;
+  // Only accept exact values.
+  if (IsConstant(info1, kExact, &v1) && IsConstant(info2, kExact, &v2)) {
+    int64_t value = v1 ^ v2;
+    if (CanLongValueFitIntoInt(value)) {
+      return Value(static_cast<int32_t>(value));
+    }
+  }
+  return Value();
+}
+
 InductionVarRange::Value InductionVarRange::MulRangeAndConstant(
     int64_t value,
     HInductionVarAnalysis::InductionInfo* info,