Recompute dominator tree after DCE.

bug:22031382
Change-Id: Ifebe169897b76872015e3ce0ed7d0a9662f80cef

1 files changed, 9 insertions, 0 deletions

diff --git a/compiler/optimizing/dead_code_elimination.cc b/compiler/optimizing/dead_code_elimination.cc
index fdfe518e95..5de629d605 100644
--- a/compiler/optimizing/dead_code_elimination.cc
+++ b/compiler/optimizing/dead_code_elimination.cc
@@ -68,6 +68,7 @@ void HDeadCodeElimination::RemoveDeadBlocks() {
   ArenaBitVector affected_loops(allocator, graph_->GetBlocks().Size(), false);
 
   MarkReachableBlocks(graph_->GetEntryBlock(), &live_blocks);
+  bool removed_one_or_more_blocks = false;
 
   // Remove all dead blocks. Iterate in post order because removal needs the
   // block's chain of dominators and nested loops need to be updated from the
@@ -84,9 +85,17 @@ void HDeadCodeElimination::RemoveDeadBlocks() {
       MaybeRecordDeadBlock(block);
       MarkLoopHeadersContaining(*block, &affected_loops);
       block->DisconnectAndDelete();
+      removed_one_or_more_blocks = true;
     }
   }
 
+  // If we removed at least one block, we need to recompute the full
+  // dominator tree.
+  if (removed_one_or_more_blocks) {
+    graph_->ClearDominanceInformation();
+    graph_->ComputeDominanceInformation();
+  }
+
   // Connect successive blocks created by dead branches. Order does not matter.
   for (HReversePostOrderIterator it(*graph_); !it.Done();) {
     HBasicBlock* block  = it.Current();