CHA guard optimization (elimination/hoisting).

Test: manual by checking the dump-cfg output.

Change-Id: I254e168b9a85d2d3d23e02eea7e129c1bc9ab920

1 files changed, 26 insertions, 18 deletions

diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 4a77bed44a..6cfaa86b38 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -330,6 +330,7 @@ class HGraph : public ArenaObject<kArenaAllocGraph> {
         invoke_type_(invoke_type),
         in_ssa_form_(false),
         should_generate_constructor_barrier_(should_generate_constructor_barrier),
+        number_of_cha_guards_(0),
         instruction_set_(instruction_set),
         cached_null_constant_(nullptr),
         cached_int_constants_(std::less<int32_t>(), arena->Adapter(kArenaAllocConstantsMap)),
@@ -551,9 +552,7 @@ class HGraph : public ArenaObject<kArenaAllocGraph> {
   }
 
   bool HasShouldDeoptimizeFlag() const {
-    // TODO: if all CHA guards can be eliminated, there is no need for the flag
-    // even if cha_single_implementation_list_ is not empty.
-    return !cha_single_implementation_list_.empty();
+    return number_of_cha_guards_ != 0;
   }
 
   bool HasTryCatch() const { return has_try_catch_; }
@@ -572,6 +571,10 @@ class HGraph : public ArenaObject<kArenaAllocGraph> {
 
   ReferenceTypeInfo GetInexactObjectRti() const { return inexact_object_rti_; }
 
+  uint32_t GetNumberOfCHAGuards() { return number_of_cha_guards_; }
+  void SetNumberOfCHAGuards(uint32_t num) { number_of_cha_guards_ = num; }
+  void IncrementNumberOfCHAGuards() { number_of_cha_guards_++; }
+
  private:
   void RemoveInstructionsAsUsersFromDeadBlocks(const ArenaBitVector& visited) const;
   void RemoveDeadBlocks(const ArenaBitVector& visited);
@@ -667,6 +670,10 @@ class HGraph : public ArenaObject<kArenaAllocGraph> {
 
   const bool should_generate_constructor_barrier_;
 
+  // Number of CHA guards in the graph. Used to short-circuit the
+  // CHA guard optimization pass when there is no CHA guard left.
+  uint32_t number_of_cha_guards_;
+
   const InstructionSet instruction_set_;
 
   // Cached constants.
@@ -2349,6 +2356,11 @@ class HBackwardInstructionIterator : public ValueObject {
 
 class HVariableInputSizeInstruction : public HInstruction {
  public:
+  using HInstruction::GetInputRecords;  // Keep the const version visible.
+  ArrayRef<HUserRecord<HInstruction*>> GetInputRecords() OVERRIDE {
+    return ArrayRef<HUserRecord<HInstruction*>>(inputs_);
+  }
+
   void AddInput(HInstruction* input);
   void InsertInputAt(size_t index, HInstruction* input);
   void RemoveInputAt(size_t index);
@@ -2489,11 +2501,6 @@ class HPhi FINAL : public HVariableInputSizeInstruction {
 
   bool IsCatchPhi() const { return GetBlock()->IsCatchBlock(); }
 
-  using HInstruction::GetInputRecords;  // Keep the const version visible.
-  ArrayRef<HUserRecord<HInstruction*>> GetInputRecords() OVERRIDE FINAL {
-    return ArrayRef<HUserRecord<HInstruction*>>(inputs_);
-  }
-
   Primitive::Type GetType() const OVERRIDE { return GetPackedField<TypeField>(); }
   void SetType(Primitive::Type new_type) {
     // Make sure that only valid type changes occur. The following are allowed:
@@ -2925,14 +2932,20 @@ class HDeoptimize FINAL : public HTemplateInstruction<1> {
 // if it's true, starts to do deoptimization.
 // It has a 4-byte slot on stack.
 // TODO: allocate a register for this flag.
-class HShouldDeoptimizeFlag FINAL : public HExpression<0> {
+class HShouldDeoptimizeFlag FINAL : public HVariableInputSizeInstruction {
  public:
-  // TODO: use SideEffects to aid eliminating some CHA guards.
-  explicit HShouldDeoptimizeFlag(uint32_t dex_pc)
-      : HExpression(Primitive::kPrimInt, SideEffects::None(), dex_pc) {
+  // CHA guards are only optimized in a separate pass and it has no side effects
+  // with regard to other passes.
+  HShouldDeoptimizeFlag(ArenaAllocator* arena, uint32_t dex_pc)
+      : HVariableInputSizeInstruction(SideEffects::None(), dex_pc, arena, 0, kArenaAllocCHA) {
   }
 
-  // We don't eliminate CHA guards yet.
+  Primitive::Type GetType() const OVERRIDE { return Primitive::kPrimInt; }
+
+  // We do all CHA guard elimination/motion in a single pass, after which there is no
+  // further guard elimination/motion since a guard might have been used for justification
+  // of the elimination of another guard. Therefore, we pretend this guard cannot be moved
+  // to avoid other optimizations trying to move it.
   bool CanBeMoved() const OVERRIDE { return false; }
 
   DECLARE_INSTRUCTION(ShouldDeoptimizeFlag);
@@ -3816,11 +3829,6 @@ class HInvoke : public HVariableInputSizeInstruction {
  public:
   bool NeedsEnvironment() const OVERRIDE;
 
-  using HInstruction::GetInputRecords;  // Keep the const version visible.
-  ArrayRef<HUserRecord<HInstruction*>> GetInputRecords() OVERRIDE {
-    return ArrayRef<HUserRecord<HInstruction*>>(inputs_);
-  }
-
   void SetArgumentAt(size_t index, HInstruction* argument) {
     SetRawInputAt(index, argument);
   }