Remove dead blocks for the blocks_ array.
This prevents crashing because of structurally incorrect
blocks. Also we now don't need to remove its instructions.
Test case courtesy of Serguei I Katkov.
Change-Id: Ia3ef9580549fc3546e8cd5f346079b1f0ceb2a61
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index d8a8554..ada3487 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -51,9 +51,7 @@
for (size_t i = 0; i < blocks_.Size(); ++i) {
if (!visited.IsBitSet(i)) {
HBasicBlock* block = blocks_.Get(i);
- for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
- RemoveAsUser(it.Current());
- }
+ DCHECK(block->GetPhis().IsEmpty()) << "Phis are not inserted at this stage";
for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
RemoveAsUser(it.Current());
}
@@ -61,19 +59,17 @@
}
}
-void HGraph::RemoveDeadBlocks(const ArenaBitVector& visited) const {
+void HGraph::RemoveDeadBlocks(const ArenaBitVector& visited) {
for (size_t i = 0; i < blocks_.Size(); ++i) {
if (!visited.IsBitSet(i)) {
HBasicBlock* block = blocks_.Get(i);
+ // We only need to update the successor, which might be live.
for (size_t j = 0; j < block->GetSuccessors().Size(); ++j) {
block->GetSuccessors().Get(j)->RemovePredecessor(block);
}
- for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
- block->RemovePhi(it.Current()->AsPhi(), /*ensure_safety=*/ false);
- }
- for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
- block->RemoveInstruction(it.Current(), /*ensure_safety=*/ false);
- }
+ // Remove the block from the list of blocks, so that further analyses
+ // never see it.
+ blocks_.Put(i, nullptr);
}
}
}
@@ -258,6 +254,7 @@
// (2): Simplify loops by having only one back edge, and one preheader.
for (size_t i = 0; i < blocks_.Size(); ++i) {
HBasicBlock* block = blocks_.Get(i);
+ if (block == nullptr) continue;
if (block->GetSuccessors().Size() > 1) {
for (size_t j = 0; j < block->GetSuccessors().Size(); ++j) {
HBasicBlock* successor = block->GetSuccessors().Get(j);
@@ -274,8 +271,9 @@
}
bool HGraph::AnalyzeNaturalLoops() const {
- for (size_t i = 0; i < blocks_.Size(); ++i) {
- HBasicBlock* block = blocks_.Get(i);
+ // Order does not matter.
+ for (HReversePostOrderIterator it(*this); !it.Done(); it.Advance()) {
+ HBasicBlock* block = it.Current();
if (block->IsLoopHeader()) {
HLoopInformation* info = block->GetLoopInformation();
if (!info->Populate()) {