Add a new helper RecomputeDominatorTree

It clears loop and dominance information, and builds the dominator
tree. It also dchecks that we are not calling this methods with
irreducible loops, as it is not supported.

When adding this helper we found a partial LSE bug as it was
recomputing dominator tree for irreducible loops.

Test: art/test/testrunner/testrunner.py --host --64 -b --optimizing
Bug: 304749506
Change-Id: Ia4cc72cd19779ad881fa686e52b43679fe5a64d3

5 files changed, 20 insertions, 33 deletions

diff --git a/compiler/optimizing/dead_code_elimination.cc b/compiler/optimizing/dead_code_elimination.cc
index 8e6b6db236..5a7b83603f 100644
--- a/compiler/optimizing/dead_code_elimination.cc
+++ b/compiler/optimizing/dead_code_elimination.cc
@@ -312,9 +312,7 @@ bool HDeadCodeElimination::SimplifyAlwaysThrows() {
 
   // We need to re-analyze the graph in order to run DCE afterwards.
   if (rerun_dominance_and_loop_analysis) {
-    graph_->ClearLoopInformation();
-    graph_->ClearDominanceInformation();
-    graph_->BuildDominatorTree();
+    graph_->RecomputeDominatorTree();
     return true;
   }
   return false;
@@ -438,9 +436,7 @@ bool HDeadCodeElimination::SimplifyIfs() {
   // We need to re-analyze the graph in order to run DCE afterwards.
   if (simplified_one_or_more_ifs) {
     if (rerun_dominance_and_loop_analysis) {
-      graph_->ClearLoopInformation();
-      graph_->ClearDominanceInformation();
-      graph_->BuildDominatorTree();
+      graph_->RecomputeDominatorTree();
     } else {
       graph_->ClearDominanceInformation();
       // We have introduced critical edges, remove them.
@@ -808,9 +804,7 @@ bool HDeadCodeElimination::RemoveDeadBlocks(bool force_recomputation,
   // dominator tree and try block membership.
   if (removed_one_or_more_blocks || force_recomputation) {
     if (rerun_dominance_and_loop_analysis || force_loop_recomputation) {
-      graph_->ClearLoopInformation();
-      graph_->ClearDominanceInformation();
-      graph_->BuildDominatorTree();
+      graph_->RecomputeDominatorTree();
     } else {
       graph_->ClearDominanceInformation();
       graph_->ComputeDominanceInformation();
diff --git a/compiler/optimizing/load_store_elimination.cc b/compiler/optimizing/load_store_elimination.cc
index 58fdd1cd05..36c3770c42 100644
--- a/compiler/optimizing/load_store_elimination.cc
+++ b/compiler/optimizing/load_store_elimination.cc
@@ -1364,7 +1364,9 @@ class LSEVisitor final : private HGraphDelegateVisitor {
   }
 
   bool ShouldPerformPartialLSE() const {
-    return perform_partial_lse_ && !GetGraph()->IsCompilingOsr();
+    return perform_partial_lse_ &&
+           !GetGraph()->IsCompilingOsr() &&
+           !GetGraph()->HasIrreducibleLoops();
   }
 
   bool perform_partial_lse_;
@@ -3072,10 +3074,8 @@ class PartialLoadStoreEliminationHelper {
                                        Handle<mirror::DexCache>(),
                                        /* is_first_run= */ false);
     rtp_fixup.Visit(ArrayRef<HInstruction* const>(new_ref_phis_));
-    GetGraph()->ClearLoopInformation();
-    GetGraph()->ClearDominanceInformation();
     GetGraph()->ClearReachabilityInformation();
-    GetGraph()->BuildDominatorTree();
+    GetGraph()->RecomputeDominatorTree();
     GetGraph()->ComputeReachabilityInformation();
   }
 
diff --git a/compiler/optimizing/load_store_elimination_test.cc b/compiler/optimizing/load_store_elimination_test.cc
index d3cf8bfa2a..eb0711343d 100644
--- a/compiler/optimizing/load_store_elimination_test.cc
+++ b/compiler/optimizing/load_store_elimination_test.cc
@@ -8111,21 +8111,10 @@ TEST_F(LoadStoreEliminationTest, PartialIrreducibleLoop) {
   EXPECT_TRUE(loop_header->IsLoopHeader());
   EXPECT_TRUE(loop_header->GetLoopInformation()->IsIrreducible());
 
+  // Partial LSE cannot run with irreducible loops.
   EXPECT_INS_RETAINED(left_set);
-  EXPECT_INS_REMOVED(write_start);
-  EXPECT_INS_REMOVED(read_end);
-
-  HPredicatedInstanceFieldGet* pred_get =
-      FindSingleInstruction<HPredicatedInstanceFieldGet>(graph_, breturn);
-  ASSERT_NE(pred_get, nullptr);
-  ASSERT_TRUE(pred_get->GetDefaultValue()->IsPhi()) << pred_get->DumpWithArgs();
-  EXPECT_INS_EQ(pred_get->GetDefaultValue()->InputAt(0), c11);
-  EXPECT_INS_EQ(pred_get->GetDefaultValue()->InputAt(1), graph_->GetIntConstant(0));
-  ASSERT_TRUE(pred_get->GetTarget()->IsPhi()) << pred_get->DumpWithArgs();
-  EXPECT_INS_EQ(pred_get->GetTarget()->InputAt(0), graph_->GetNullConstant());
-  HNewInstance* mat = FindSingleInstruction<HNewInstance>(graph_, right->GetSinglePredecessor());
-  ASSERT_NE(mat, nullptr);
-  EXPECT_INS_EQ(pred_get->GetTarget()->InputAt(1), mat);
+  EXPECT_INS_RETAINED(write_start);
+  EXPECT_INS_RETAINED(read_end);
 }
 
 enum class UsesOrder { kDefaultOrder, kReverseOrder };
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 5795ea7ca9..53ed49a307 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -255,6 +255,14 @@ GraphAnalysisResult HGraph::BuildDominatorTree() {
   return kAnalysisSuccess;
 }
 
+GraphAnalysisResult HGraph::RecomputeDominatorTree() {
+  DCHECK(!HasIrreducibleLoops()) << "Recomputing loop information in graphs with irreducible loops "
+                                 << "is unsupported, as it could lead to loop header changes";
+  ClearLoopInformation();
+  ClearDominanceInformation();
+  return BuildDominatorTree();
+}
+
 void HGraph::ClearDominanceInformation() {
   for (HBasicBlock* block : GetActiveBlocks()) {
     block->ClearDominanceInformation();
@@ -3001,12 +3009,7 @@ HInstruction* HGraph::InlineInto(HGraph* outer_graph, HInvoke* invoke) {
       }
     }
     if (rerun_loop_analysis) {
-      DCHECK(!outer_graph->HasIrreducibleLoops())
-          << "Recomputing loop information in graphs with irreducible loops "
-          << "is unsupported, as it could lead to loop header changes";
-      outer_graph->ClearLoopInformation();
-      outer_graph->ClearDominanceInformation();
-      outer_graph->BuildDominatorTree();
+      outer_graph->RecomputeDominatorTree();
     } else if (rerun_dominance) {
       outer_graph->ClearDominanceInformation();
       outer_graph->ComputeDominanceInformation();
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 9cf52183b8..3613b9519b 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -467,6 +467,7 @@ class HGraph : public ArenaObject<kArenaAllocGraph> {
   void ClearLoopInformation();
   void FindBackEdges(ArenaBitVector* visited);
   GraphAnalysisResult BuildDominatorTree();
+  GraphAnalysisResult RecomputeDominatorTree();
   void SimplifyCFG();
   void SimplifyCatchBlocks();