Fix null pointer check elimination for catch entries.

Remove the special treatment of catch blocks for null
pointer check elimination and class initialization check
elimination. In both cases this can help optimizing
previously missed cases. In the null check case, this
avoids incorrect optimization as exposed by the new test.

Bug: 16230771
Change-Id: I834b7a1835d9ca8572f4f8d8516d93913c701ad1

2 files changed, 32 insertions, 18 deletions

diff --git a/compiler/dex/mir_optimization.cc b/compiler/dex/mir_optimization.cc
index 869c48f66..f69eea7fb 100644
--- a/compiler/dex/mir_optimization.cc
+++ b/compiler/dex/mir_optimization.cc
@@ -737,11 +737,9 @@ bool MIRGraph::EliminateNullChecksAndInferTypes(BasicBlock* bb) {
   ArenaBitVector* ssa_regs_to_check = temp_bit_vector_;
   if (do_nce) {
     /*
-     * Set initial state.  Be conservative with catch
-     * blocks and start with no assumptions about null check
-     * status (except for "this").
+     * Set initial state. Catch blocks don't need any special treatment.
      */
-    if ((bb->block_type == kEntryBlock) | bb->catch_entry) {
+    if (bb->block_type == kEntryBlock) {
       ssa_regs_to_check->ClearAllBits();
       // Assume all ins are objects.
       for (uint16_t in_reg = cu_->num_dalvik_registers - cu_->num_ins;
@@ -1047,12 +1045,11 @@ bool MIRGraph::EliminateClassInitChecks(BasicBlock* bb) {
   }
 
   /*
-   * Set initial state.  Be conservative with catch
-   * blocks and start with no assumptions about class init check status.
+   * Set initial state.  Catch blocks don't need any special treatment.
    */
   ArenaBitVector* classes_to_check = temp_bit_vector_;
   DCHECK(classes_to_check != nullptr);
-  if ((bb->block_type == kEntryBlock) | bb->catch_entry) {
+  if (bb->block_type == kEntryBlock) {
     classes_to_check->SetInitialBits(temp_bit_vector_size_);
   } else if (bb->predecessors->Size() == 1) {
     BasicBlock* pred_bb = GetBasicBlock(bb->predecessors->Get(0));
diff --git a/compiler/dex/mir_optimization_test.cc b/compiler/dex/mir_optimization_test.cc
index 8c70b5c75..4a0cf5c78 100644
--- a/compiler/dex/mir_optimization_test.cc
+++ b/compiler/dex/mir_optimization_test.cc
@@ -373,30 +373,47 @@ TEST_F(ClassInitCheckEliminationTest, Catch) {
   static const SFieldDef sfields[] = {
       { 0u, 1u, 0u, 0u },
       { 1u, 1u, 1u, 1u },
+      { 2u, 1u, 2u, 2u },
+      { 3u, 1u, 3u, 3u },
   };
   static const BBDef bbs[] = {
       DEF_BB(kNullBlock, DEF_SUCC0(), DEF_PRED0()),
       DEF_BB(kEntryBlock, DEF_SUCC1(3), DEF_PRED0()),
-      DEF_BB(kExitBlock, DEF_SUCC0(), DEF_PRED1(5)),
-      DEF_BB(kDalvikByteCode, DEF_SUCC2(5, 4), DEF_PRED1(1)),
-      DEF_BB(kDalvikByteCode, DEF_SUCC1(5), DEF_PRED1(3)),  // Catch handler.
-      DEF_BB(kDalvikByteCode, DEF_SUCC1(2), DEF_PRED2(3, 4)),
+      DEF_BB(kExitBlock, DEF_SUCC0(), DEF_PRED1(6)),
+      DEF_BB(kDalvikByteCode, DEF_SUCC1(4), DEF_PRED1(1)),     // The top.
+      DEF_BB(kDalvikByteCode, DEF_SUCC1(6), DEF_PRED1(3)),     // The throwing insn.
+      DEF_BB(kDalvikByteCode, DEF_SUCC1(6), DEF_PRED1(3)),     // Catch handler.
+      DEF_BB(kDalvikByteCode, DEF_SUCC1(2), DEF_PRED2(4, 5)),  // The merged block.
   };
   static const MIRDef mirs[] = {
-      DEF_MIR(Instruction::SGET, 3u, 0u),
-      DEF_MIR(Instruction::SGET, 3u, 1u),
-      DEF_MIR(Instruction::SGET, 4u, 1u),
-      DEF_MIR(Instruction::SGET, 5u, 0u),  // Not eliminated.
-      DEF_MIR(Instruction::SGET, 5u, 1u),  // Eliminated.
+      DEF_MIR(Instruction::SGET, 3u, 0u),  // Before the exception edge.
+      DEF_MIR(Instruction::SGET, 3u, 1u),  // Before the exception edge.
+      DEF_MIR(Instruction::SGET, 4u, 2u),  // After the exception edge.
+      DEF_MIR(Instruction::SGET, 4u, 3u),  // After the exception edge.
+      DEF_MIR(Instruction::SGET, 5u, 0u),  // In catch handler; class init check eliminated.
+      DEF_MIR(Instruction::SGET, 5u, 2u),  // In catch handler; class init check not eliminated.
+      DEF_MIR(Instruction::SGET, 6u, 0u),  // Class init check eliminated.
+      DEF_MIR(Instruction::SGET, 6u, 1u),  // Class init check eliminated.
+      DEF_MIR(Instruction::SGET, 6u, 2u),  // Class init check eliminated.
+      DEF_MIR(Instruction::SGET, 6u, 3u),  // Class init check not eliminated.
   };
   static const bool expected_ignore_clinit_check[] = {
-      false, false, false, false, true
+      false, false, false, false, true, false, true, true, true, false
   };
 
   PrepareSFields(sfields);
   PrepareBasicBlocks(bbs);
-  BasicBlock* catch_handler = cu_.mir_graph->GetBasicBlock(4u);
+  BasicBlock* catch_handler = cu_.mir_graph->GetBasicBlock(5u);
   catch_handler->catch_entry = true;
+  // Add successor block info to the check block.
+  BasicBlock* check_bb = cu_.mir_graph->GetBasicBlock(3u);
+  check_bb->successor_block_list_type = kCatch;
+  check_bb->successor_blocks = new (&cu_.arena) GrowableArray<SuccessorBlockInfo*>(
+      &cu_.arena, 2, kGrowableArraySuccessorBlocks);
+  SuccessorBlockInfo* successor_block_info = reinterpret_cast<SuccessorBlockInfo*>
+      (cu_.arena.Alloc(sizeof(SuccessorBlockInfo), kArenaAllocSuccessor));
+  successor_block_info->block = catch_handler->id;
+  check_bb->successor_blocks->Insert(successor_block_info);
   PrepareMIRs(mirs);
   PerformClassInitCheckElimination();
   ASSERT_EQ(arraysize(expected_ignore_clinit_check), mir_count_);