Revert "Revert "Do not update the type of something we already know.""

This reverts commit 63107a804ce17db9789051e1fe310d99d1dae1cb.

bug:22116987

(cherry picked from commit f9a199571417b5a5a62d94d05a064077e14dd2c4)

Change-Id: Ia516f2cbce6d22df37f3a0854abdd0b54d3ea72d

3 files changed, 37 insertions, 0 deletions

diff --git a/compiler/optimizing/graph_checker.cc b/compiler/optimizing/graph_checker.cc
index fd28f0b..44c4101 100644
--- a/compiler/optimizing/graph_checker.cc
+++ b/compiler/optimizing/graph_checker.cc
@@ -253,6 +253,30 @@ void GraphChecker::VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) {
   }
 }
 
+void GraphChecker::VisitCheckCast(HCheckCast* check) {
+  VisitInstruction(check);
+  HInstruction* input = check->InputAt(1);
+  if (!input->IsLoadClass()) {
+    AddError(StringPrintf("%s:%d expects a HLoadClass as second input, not %s:%d.",
+                          check->DebugName(),
+                          check->GetId(),
+                          input->DebugName(),
+                          input->GetId()));
+  }
+}
+
+void GraphChecker::VisitInstanceOf(HInstanceOf* instruction) {
+  VisitInstruction(instruction);
+  HInstruction* input = instruction->InputAt(1);
+  if (!input->IsLoadClass()) {
+    AddError(StringPrintf("%s:%d expects a HLoadClass as second input, not %s:%d.",
+                          instruction->DebugName(),
+                          instruction->GetId(),
+                          input->DebugName(),
+                          input->GetId()));
+  }
+}
+
 void SSAChecker::VisitBasicBlock(HBasicBlock* block) {
   super_type::VisitBasicBlock(block);
 
diff --git a/compiler/optimizing/graph_checker.h b/compiler/optimizing/graph_checker.h
index b4314da..9284bb7 100644
--- a/compiler/optimizing/graph_checker.h
+++ b/compiler/optimizing/graph_checker.h
@@ -48,6 +48,10 @@ class GraphChecker : public HGraphDelegateVisitor {
   // Check that the HasBoundsChecks() flag is set for bounds checks.
   void VisitBoundsCheck(HBoundsCheck* check) OVERRIDE;
 
+  // Check that HCheckCast and HInstanceOf have HLoadClass as second input.
+  void VisitCheckCast(HCheckCast* check) OVERRIDE;
+  void VisitInstanceOf(HInstanceOf* check) OVERRIDE;
+
   // Was the last visit of the graph valid?
   bool IsValid() const {
     return errors_.empty();
diff --git a/compiler/optimizing/reference_type_propagation.cc b/compiler/optimizing/reference_type_propagation.cc
index e93e061..302366e 100644
--- a/compiler/optimizing/reference_type_propagation.cc
+++ b/compiler/optimizing/reference_type_propagation.cc
@@ -130,6 +130,15 @@ void ReferenceTypePropagation::BoundTypeForIfInstanceOf(HBasicBlock* block) {
   HBoundType* bound_type = nullptr;
 
   HInstruction* obj = instanceOf->InputAt(0);
+  if (obj->GetReferenceTypeInfo().IsExact() && !obj->IsPhi()) {
+    // This method is being called while doing a fixed-point calculation
+    // over phis. Non-phis instruction whose type is already known do
+    // not need to be bound to another type.
+    // Not that this also prevents replacing `HLoadClass` with a `HBoundType`.
+    // `HCheckCast` and `HInstanceOf` expect a `HLoadClass` as a second
+    // input.
+    return;
+  }
   for (HUseIterator<HInstruction*> it(obj->GetUses()); !it.Done(); it.Advance()) {
     HInstruction* user = it.Current()->GetUser();
     if (instanceOfTrueBlock->Dominates(user->GetBlock())) {