1 files changed, 61 insertions, 13 deletions

diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index ca48e08a7c..ddd798b4a5 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -90,7 +90,8 @@ void HGraph::FindBackEdges(ArenaBitVector* visited) {
   }
 }
 
-static void RemoveEnvironmentUses(HInstruction* instruction) {
+// Remove the environment use records of the instruction for users.
+void RemoveEnvironmentUses(HInstruction* instruction) {
   for (HEnvironment* environment = instruction->GetEnvironment();
        environment != nullptr;
        environment = environment->GetParent()) {
@@ -102,6 +103,35 @@ static void RemoveEnvironmentUses(HInstruction* instruction) {
   }
 }
 
+// Return whether the instruction has an environment and it's used by others.
+bool HasEnvironmentUsedByOthers(HInstruction* instruction) {
+  for (HEnvironment* environment = instruction->GetEnvironment();
+       environment != nullptr;
+       environment = environment->GetParent()) {
+    for (size_t i = 0, e = environment->Size(); i < e; ++i) {
+      HInstruction* user = environment->GetInstructionAt(i);
+      if (user != nullptr) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+// Reset environment records of the instruction itself.
+void ResetEnvironmentInputRecords(HInstruction* instruction) {
+  for (HEnvironment* environment = instruction->GetEnvironment();
+       environment != nullptr;
+       environment = environment->GetParent()) {
+    for (size_t i = 0, e = environment->Size(); i < e; ++i) {
+      DCHECK(environment->GetHolder() == instruction);
+      if (environment->GetInstructionAt(i) != nullptr) {
+        environment->SetRawEnvAt(i, nullptr);
+      }
+    }
+  }
+}
+
 static void RemoveAsUser(HInstruction* instruction) {
   instruction->RemoveAsUserOfAllInputs();
   RemoveEnvironmentUses(instruction);
@@ -328,6 +358,35 @@ void HGraph::SplitCriticalEdge(HBasicBlock* block, HBasicBlock* successor) {
   }
 }
 
+// Reorder phi inputs to match reordering of the block's predecessors.
+static void FixPhisAfterPredecessorsReodering(HBasicBlock* block, size_t first, size_t second) {
+  for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
+    HPhi* phi = it.Current()->AsPhi();
+    HInstruction* first_instr = phi->InputAt(first);
+    HInstruction* second_instr = phi->InputAt(second);
+    phi->ReplaceInput(first_instr, second);
+    phi->ReplaceInput(second_instr, first);
+  }
+}
+
+// Make sure that the first predecessor of a loop header is the incoming block.
+void HGraph::OrderLoopHeaderPredecessors(HBasicBlock* header) {
+  DCHECK(header->IsLoopHeader());
+  HLoopInformation* info = header->GetLoopInformation();
+  if (info->IsBackEdge(*header->GetPredecessors()[0])) {
+    HBasicBlock* to_swap = header->GetPredecessors()[0];
+    for (size_t pred = 1, e = header->GetPredecessors().size(); pred < e; ++pred) {
+      HBasicBlock* predecessor = header->GetPredecessors()[pred];
+      if (!info->IsBackEdge(*predecessor)) {
+        header->predecessors_[pred] = to_swap;
+        header->predecessors_[0] = predecessor;
+        FixPhisAfterPredecessorsReodering(header, 0, pred);
+        break;
+      }
+    }
+  }
+}
+
 void HGraph::SimplifyLoop(HBasicBlock* header) {
   HLoopInformation* info = header->GetLoopInformation();
 
@@ -351,18 +410,7 @@ void HGraph::SimplifyLoop(HBasicBlock* header) {
     pre_header->AddSuccessor(header);
   }
 
-  // Make sure the first predecessor of a loop header is the incoming block.
-  if (info->IsBackEdge(*header->GetPredecessors()[0])) {
-    HBasicBlock* to_swap = header->GetPredecessors()[0];
-    for (size_t pred = 1, e = header->GetPredecessors().size(); pred < e; ++pred) {
-      HBasicBlock* predecessor = header->GetPredecessors()[pred];
-      if (!info->IsBackEdge(*predecessor)) {
-        header->predecessors_[pred] = to_swap;
-        header->predecessors_[0] = predecessor;
-        break;
-      }
-    }
-  }
+  OrderLoopHeaderPredecessors(header);
 
   HInstruction* first_instruction = header->GetFirstInstruction();
   if (first_instruction != nullptr && first_instruction->IsSuspendCheck()) {