5 files changed, 22 insertions, 2 deletions
diff --git a/compiler/optimizing/gvn.cc b/compiler/optimizing/gvn.cc
index cd3b07065c..8a5a4742ba 100644
--- a/compiler/optimizing/gvn.cc
+++ b/compiler/optimizing/gvn.cc
@@ -359,7 +359,8 @@ class GlobalValueNumberer : public ValueObject {
         side_effects_(side_effects),
         sets_(graph->GetBlocks().size(), nullptr, allocator_.Adapter(kArenaAllocGvn)),
         visited_blocks_(
-            &allocator_, graph->GetBlocks().size(), /* expandable= */ false, kArenaAllocGvn) {}
+            &allocator_, graph->GetBlocks().size(), /* expandable= */ false, kArenaAllocGvn),
+        did_optimization_(false) {}
 
   bool Run();
 
@@ -403,6 +404,9 @@ class GlobalValueNumberer : public ValueObject {
   // visited/unvisited Boolean.
   ArenaBitVector visited_blocks_;
 
+  // True if GVN did at least one removal.
+  bool did_optimization_;
+
   DISALLOW_COPY_AND_ASSIGN(GlobalValueNumberer);
 };
 
@@ -415,7 +419,7 @@ bool GlobalValueNumberer::Run() {
   for (HBasicBlock* block : graph_->GetReversePostOrder()) {
     VisitBasicBlock(block);
   }
-  return true;
+  return did_optimization_;
 }
 
 void GlobalValueNumberer::VisitBasicBlock(HBasicBlock* block) {
@@ -508,6 +512,7 @@ void GlobalValueNumberer::VisitBasicBlock(HBasicBlock* block) {
         // Or current is used by a phi, and we don't do OrderInputs() on a phi anyway.
         current->ReplaceWith(existing);
         current->GetBlock()->RemoveInstruction(current);
+        did_optimization_ = true;
       } else {
         set->Kill(current->GetSideEffects());
         set->Add(current);
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index abc5dae016..931050855c 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -709,6 +709,9 @@ bool InstructionSimplifierVisitor::TryReplaceWithRotateRegisterSubPattern(HBinar
 
 void InstructionSimplifierVisitor::VisitNullCheck(HNullCheck* null_check) {
   HInstruction* obj = null_check->InputAt(0);
+  // Note we don't do `CanEnsureNotNullAt` here. If we do that, we may get rid of a NullCheck but
+  // what we should do instead is coalesce them. This is what GVN does, and so InstructionSimplifier
+  // doesn't do this.
   if (!obj->CanBeNull()) {
     null_check->ReplaceWith(obj);
     null_check->GetBlock()->RemoveInstruction(null_check);
diff --git a/compiler/optimizing/optimization.cc b/compiler/optimizing/optimization.cc
index ef1f36ab08..bd8fbdf1d2 100644
--- a/compiler/optimizing/optimization.cc
+++ b/compiler/optimizing/optimization.cc
@@ -55,6 +55,7 @@
 #include "licm.h"
 #include "load_store_elimination.h"
 #include "loop_optimization.h"
+#include "reference_type_propagation.h"
 #include "scheduler.h"
 #include "select_generator.h"
 #include "sharpening.h"
@@ -98,6 +99,8 @@ const char* OptimizationPassName(OptimizationPass pass) {
       return CodeSinking::kCodeSinkingPassName;
     case OptimizationPass::kConstructorFenceRedundancyElimination:
       return ConstructorFenceRedundancyElimination::kCFREPassName;
+    case OptimizationPass::kReferenceTypePropagation:
+      return ReferenceTypePropagation::kReferenceTypePropagationPassName;
     case OptimizationPass::kScheduling:
       return HInstructionScheduling::kInstructionSchedulingPassName;
     case OptimizationPass::kWriteBarrierElimination:
@@ -154,6 +157,7 @@ OptimizationPass OptimizationPassByName(const std::string& pass_name) {
   X(OptimizationPass::kInvariantCodeMotion);
   X(OptimizationPass::kLoadStoreElimination);
   X(OptimizationPass::kLoopOptimization);
+  X(OptimizationPass::kReferenceTypePropagation);
   X(OptimizationPass::kScheduling);
   X(OptimizationPass::kSelectGenerator);
   X(OptimizationPass::kSideEffectsAnalysis);
@@ -287,6 +291,10 @@ ArenaVector<HOptimization*> ConstructOptimizations(
       case OptimizationPass::kLoadStoreElimination:
         opt = new (allocator) LoadStoreElimination(graph, stats, pass_name);
         break;
+      case OptimizationPass::kReferenceTypePropagation:
+        opt = new (allocator) ReferenceTypePropagation(
+            graph, dex_compilation_unit.GetDexCache(), /* is_first_run= */ false, pass_name);
+        break;
       case OptimizationPass::kWriteBarrierElimination:
         opt = new (allocator) WriteBarrierElimination(graph, stats, pass_name);
         break;
diff --git a/compiler/optimizing/optimization.h b/compiler/optimizing/optimization.h
index 8bc9da49fc..abc4361b44 100644
--- a/compiler/optimizing/optimization.h
+++ b/compiler/optimizing/optimization.h
@@ -81,6 +81,7 @@ enum class OptimizationPass {
   kInvariantCodeMotion,
   kLoadStoreElimination,
   kLoopOptimization,
+  kReferenceTypePropagation,
   kScheduling,
   kSelectGenerator,
   kSideEffectsAnalysis,
diff --git a/compiler/optimizing/optimizing_compiler.cc b/compiler/optimizing/optimizing_compiler.cc
index 89edbed54d..b15657355f 100644
--- a/compiler/optimizing/optimizing_compiler.cc
+++ b/compiler/optimizing/optimizing_compiler.cc
@@ -665,6 +665,9 @@ void OptimizingCompiler::RunOptimizations(HGraph* graph,
       OptDef(OptimizationPass::kSideEffectsAnalysis,
              "side_effects$before_gvn"),
       OptDef(OptimizationPass::kGlobalValueNumbering),
+      OptDef(OptimizationPass::kReferenceTypePropagation,
+             "reference_type_propagation$after_gvn",
+             OptimizationPass::kGlobalValueNumbering),
       // Simplification (TODO: only if GVN occurred).
       OptDef(OptimizationPass::kSelectGenerator),
       OptDef(OptimizationPass::kConstantFolding,