commit 8909bafa5d64e12eb53f3d37b984f53e7a632224
author Guillaume "Vermeille" Sanchez <guillaumesa@google.com> Thu Apr 23 21:35:11 2015 +0100
committer Guillaume "Vermeille" Sanchez <guillaumesa@google.com> Mon May 18 17:58:21 2015 +0100
tree 6bac613ed796914ec4937a64d40d44b1888d4878
parent 06675720cc274eb9d91a4ecd3fb1eef94a2d88f0

Mark CheckCast's and InstanceOf's input as !CanBeNull if used before in a NullCheck

Change-Id: Ied0412a01922b40a3f5d89bed49707498582abc1

compiler/optimizing/instruction_simplifier.cc

diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 46fad17..86c4a98 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -63,6 +63,7 @@
   void VisitUShr(HUShr* instruction) OVERRIDE;
   void VisitXor(HXor* instruction) OVERRIDE;
   void VisitInstanceOf(HInstanceOf* instruction) OVERRIDE;
+  bool IsDominatedByInputNullCheck(HInstruction* instr);
 
   OptimizingCompilerStats* stats_;
   bool simplification_occurred_ = false;
@@ -170,9 +171,20 @@
   }
 }
 
+bool InstructionSimplifierVisitor::IsDominatedByInputNullCheck(HInstruction* instr) {
+  HInstruction* input = instr->InputAt(0);
+  for (HUseIterator<HInstruction*> it(input->GetUses()); !it.Done(); it.Advance()) {
+    HInstruction* use = it.Current()->GetUser();
+    if (use->IsNullCheck() && use->StrictlyDominates(instr)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 void InstructionSimplifierVisitor::VisitCheckCast(HCheckCast* check_cast) {
   HLoadClass* load_class = check_cast->InputAt(1)->AsLoadClass();
-  if (!check_cast->InputAt(0)->CanBeNull()) {
+  if (!check_cast->InputAt(0)->CanBeNull() || IsDominatedByInputNullCheck(check_cast)) {
     check_cast->ClearMustDoNullCheck();
   }
 
@@ -194,7 +206,7 @@
 }
 
 void InstructionSimplifierVisitor::VisitInstanceOf(HInstanceOf* instruction) {
-  if (!instruction->InputAt(0)->CanBeNull()) {
+  if (!instruction->InputAt(0)->CanBeNull() || IsDominatedByInputNullCheck(instruction)) {
     instruction->ClearMustDoNullCheck();
   }
 }