Remove extra uses of ClearAllBits

ArenaBitVector creation guarantees it starts empty. Add a debug
check to make sure this assumption doesn't change.

Note that ArenaAllocator guarantees zero-initialized memory but
ScopedArenaAllocators do not. This is fine either way since the
BitVector constructor calls ClearAllBits.

Bug: 329037671
Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: Icbf5e5dd1869e80b5d5828ecca9f13de30c0242b

1 files changed, 2 insertions, 5 deletions

diff --git a/compiler/optimizing/gvn.cc b/compiler/optimizing/gvn.cc
index 9113860387..cd3b07065c 100644
--- a/compiler/optimizing/gvn.cc
+++ b/compiler/optimizing/gvn.cc
@@ -353,16 +353,13 @@ class ValueSet : public ArenaObject<kArenaAllocGvn> {
  */
 class GlobalValueNumberer : public ValueObject {
  public:
-  GlobalValueNumberer(HGraph* graph,
-                      const SideEffectsAnalysis& side_effects)
+  GlobalValueNumberer(HGraph* graph, const SideEffectsAnalysis& side_effects)
       : graph_(graph),
         allocator_(graph->GetArenaStack()),
         side_effects_(side_effects),
         sets_(graph->GetBlocks().size(), nullptr, allocator_.Adapter(kArenaAllocGvn)),
         visited_blocks_(
-            &allocator_, graph->GetBlocks().size(), /* expandable= */ false, kArenaAllocGvn) {
-    visited_blocks_.ClearAllBits();
-  }
+            &allocator_, graph->GetBlocks().size(), /* expandable= */ false, kArenaAllocGvn) {}
 
   bool Run();