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, 9 insertions, 2 deletions

diff --git a/compiler/optimizing/induction_var_analysis.h b/compiler/optimizing/induction_var_analysis.h
index cd4c830645..06aee31b88 100644
--- a/compiler/optimizing/induction_var_analysis.h
+++ b/compiler/optimizing/induction_var_analysis.h
@@ -64,6 +64,7 @@ class HInductionVarAnalysis : public HOptimization {
     kNeg,
     kMul,
     kDiv,
+    kXor,
     kFetch,
     // Trip-counts.
     kTripCountInLoop,        // valid in full loop; loop is finite
@@ -171,7 +172,13 @@ class HInductionVarAnalysis : public HOptimization {
                              HInstruction* x,
                              HInstruction* y,
                              InductionOp op,
-                             bool is_first_call);
+                             bool is_first_call);  // possibly swaps x and y to try again
+  InductionInfo* SolveXor(HLoopInformation* loop,
+                          HInstruction* entry_phi,
+                          HInstruction* instruction,
+                          HInstruction* x,
+                          HInstruction* y,
+                          bool is_first_call);  // possibly swaps x and y to try again
   InductionInfo* SolveCnv(HTypeConversion* conversion);
 
   // Trip count information.
@@ -219,8 +226,8 @@ class HInductionVarAnalysis : public HOptimization {
   // Temporary book-keeping during the analysis.
   uint32_t global_depth_;
   ArenaVector<HInstruction*> stack_;
-  ArenaVector<HInstruction*> scc_;
   ArenaSafeMap<HInstruction*, NodeInfo> map_;
+  ArenaVector<HInstruction*> scc_;
   ArenaSafeMap<HInstruction*, InductionInfo*> cycle_;
   Primitive::Type type_;