ART: SBC: Support single exit loops with live_outs.
Support copying subgraphs with a single exit and live-outs -
values which are defined inside the subgraph and have uses outside.
Test: test-art-target, test-art-host.
Test: 530-checker-peel-unroll.
Change-Id: Id06a6f08d14c6e86f6437d662e24489f955e9edf
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 7f78dc2..5549660 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -1121,6 +1121,23 @@
user->FixUpUserRecordsAfterEnvUseRemoval(before_env_use_node);
}
+void HEnvironment::ReplaceInput(HInstruction* replacement, size_t index) {
+ const HUserRecord<HEnvironment*>& env_use_record = vregs_[index];
+ HInstruction* orig_instr = env_use_record.GetInstruction();
+
+ DCHECK(orig_instr != replacement);
+
+ HUseList<HEnvironment*>::iterator before_use_node = env_use_record.GetBeforeUseNode();
+ // Note: fixup_end remains valid across splice_after().
+ auto fixup_end = replacement->env_uses_.empty() ? replacement->env_uses_.begin()
+ : ++replacement->env_uses_.begin();
+ replacement->env_uses_.splice_after(replacement->env_uses_.before_begin(),
+ env_use_record.GetInstruction()->env_uses_,
+ before_use_node);
+ replacement->FixUpUserRecordsAfterEnvUseInsertion(fixup_end);
+ orig_instr->FixUpUserRecordsAfterEnvUseRemoval(before_use_node);
+}
+
HInstruction* HInstruction::GetNextDisregardingMoves() const {
HInstruction* next = GetNext();
while (next != nullptr && next->IsParallelMove()) {
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 09d9c57..3fd5b6b 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -1909,6 +1909,11 @@
void RemoveAsUserOfInput(size_t index) const;
+ // Replaces the input at the position 'index' with the replacement; the replacement and old
+ // input instructions' env_uses_ lists are adjusted. The function works similar to
+ // HInstruction::ReplaceInput.
+ void ReplaceInput(HInstruction* replacement, size_t index);
+
size_t Size() const { return vregs_.size(); }
HEnvironment* GetParent() const { return parent_; }
diff --git a/compiler/optimizing/superblock_cloner.cc b/compiler/optimizing/superblock_cloner.cc
index fad7729..1b43618 100644
--- a/compiler/optimizing/superblock_cloner.cc
+++ b/compiler/optimizing/superblock_cloner.cc
@@ -409,7 +409,7 @@
// Main algorithm methods.
//
-void SuperblockCloner::SearchForSubgraphExits(ArenaVector<HBasicBlock*>* exits) {
+void SuperblockCloner::SearchForSubgraphExits(ArenaVector<HBasicBlock*>* exits) const {
DCHECK(exits->empty());
for (uint32_t block_id : orig_bb_set_.Indexes()) {
HBasicBlock* block = GetBlockById(block_id);
@@ -521,6 +521,113 @@
}
//
+// Helpers for live-outs processing and Subgraph-closed SSA.
+//
+
+bool SuperblockCloner::CollectLiveOutsAndCheckClonable(HInstructionMap* live_outs) const {
+ DCHECK(live_outs->empty());
+ for (uint32_t idx : orig_bb_set_.Indexes()) {
+ HBasicBlock* block = GetBlockById(idx);
+
+ for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
+ HInstruction* instr = it.Current();
+ DCHECK(instr->IsClonable());
+
+ if (IsUsedOutsideRegion(instr, orig_bb_set_)) {
+ live_outs->FindOrAdd(instr, instr);
+ }
+ }
+
+ for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
+ HInstruction* instr = it.Current();
+ if (!instr->IsClonable()) {
+ return false;
+ }
+
+ if (IsUsedOutsideRegion(instr, orig_bb_set_)) {
+ // TODO: Investigate why HNewInstance, HCheckCast has a requirement for the input.
+ if (instr->IsLoadClass()) {
+ return false;
+ }
+ live_outs->FindOrAdd(instr, instr);
+ }
+ }
+ }
+ return true;
+}
+
+void SuperblockCloner::ConstructSubgraphClosedSSA() {
+ if (live_outs_.empty()) {
+ return;
+ }
+
+ ArenaVector<HBasicBlock*> exits(arena_->Adapter(kArenaAllocSuperblockCloner));
+ SearchForSubgraphExits(&exits);
+ if (exits.empty()) {
+ DCHECK(live_outs_.empty());
+ return;
+ }
+
+ DCHECK_EQ(exits.size(), 1u);
+ HBasicBlock* exit_block = exits[0];
+ // There should be no critical edges.
+ DCHECK_EQ(exit_block->GetPredecessors().size(), 1u);
+ DCHECK(exit_block->GetPhis().IsEmpty());
+
+ // For each live-out value insert a phi into the loop exit and replace all the value's uses
+ // external to the loop with this phi. The phi will have the original value as its only input;
+ // after copying is done FixSubgraphClosedSSAAfterCloning will add a corresponding copy of the
+ // original value as the second input thus merging data flow from the original and copy parts of
+ // the subgraph. Also update the record in the live_outs_ map from (value, value) to
+ // (value, new_phi).
+ for (auto live_out_it = live_outs_.begin(); live_out_it != live_outs_.end(); ++live_out_it) {
+ HInstruction* value = live_out_it->first;
+ HPhi* phi = new (arena_) HPhi(arena_, kNoRegNumber, 0, value->GetType());
+
+ if (value->GetType() == DataType::Type::kReference) {
+ phi->SetReferenceTypeInfo(value->GetReferenceTypeInfo());
+ }
+
+ exit_block->AddPhi(phi);
+ live_out_it->second = phi;
+
+ const HUseList<HInstruction*>& uses = value->GetUses();
+ for (auto it = uses.begin(), end = uses.end(); it != end; /* ++it below */) {
+ HInstruction* user = it->GetUser();
+ size_t index = it->GetIndex();
+ // Increment `it` now because `*it` may disappear thanks to user->ReplaceInput().
+ ++it;
+ if (!IsInOrigBBSet(user->GetBlock())) {
+ user->ReplaceInput(phi, index);
+ }
+ }
+
+ const HUseList<HEnvironment*>& env_uses = value->GetEnvUses();
+ for (auto it = env_uses.begin(), e = env_uses.end(); it != e; /* ++it below */) {
+ HEnvironment* env = it->GetUser();
+ size_t index = it->GetIndex();
+ ++it;
+ if (!IsInOrigBBSet(env->GetHolder()->GetBlock())) {
+ env->ReplaceInput(phi, index);
+ }
+ }
+
+ phi->AddInput(value);
+ }
+}
+
+void SuperblockCloner::FixSubgraphClosedSSAAfterCloning() {
+ for (auto it : live_outs_) {
+ DCHECK(it.first != it.second);
+ HInstruction* orig_value = it.first;
+ HPhi* phi = it.second->AsPhi();
+ HInstruction* copy_value = GetInstrCopy(orig_value);
+ // Copy edges are inserted after the original so we can just add new input to the phi.
+ phi->AddInput(copy_value);
+ }
+}
+
+//
// Debug and logging methods.
//
@@ -644,7 +751,6 @@
}
void SuperblockCloner::DumpInputSets() {
- std::cout << graph_->PrettyMethod() << "\n";
std::cout << "orig_bb_set:\n";
for (uint32_t idx : orig_bb_set_.Indexes()) {
std::cout << idx << "\n";
@@ -680,7 +786,9 @@
bb_map_(bb_map),
hir_map_(hir_map),
outer_loop_(nullptr),
- outer_loop_bb_set_(arena_, orig_bb_set->GetSizeOf(), true, kArenaAllocSuperblockCloner) {
+ outer_loop_bb_set_(arena_, orig_bb_set->GetSizeOf(), true, kArenaAllocSuperblockCloner),
+ live_outs_(std::less<HInstruction*>(),
+ graph->GetAllocator()->Adapter(kArenaAllocSuperblockCloner)) {
orig_bb_set_.Copy(orig_bb_set);
}
@@ -699,26 +807,19 @@
return false;
}
- // Check that there are no instructions defined in the subgraph and used outside.
- // TODO: Improve this by accepting graph with such uses but only one exit.
- for (uint32_t idx : orig_bb_set_.Indexes()) {
- HBasicBlock* block = GetBlockById(idx);
+ HInstructionMap live_outs(
+ std::less<HInstruction*>(), graph_->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
- for (HInstructionIterator it(block->GetInstructions()); !it.Done(); it.Advance()) {
- HInstruction* instr = it.Current();
- if (!instr->IsClonable() ||
- IsUsedOutsideRegion(instr, orig_bb_set_)) {
- return false;
- }
- }
+ if (!CollectLiveOutsAndCheckClonable(&live_outs)) {
+ return false;
+ }
- for (HInstructionIterator it(block->GetPhis()); !it.Done(); it.Advance()) {
- HInstruction* instr = it.Current();
- if (!instr->IsClonable() ||
- IsUsedOutsideRegion(instr, orig_bb_set_)) {
- return false;
- }
- }
+ ArenaVector<HBasicBlock*> exits(arena_->Adapter(kArenaAllocSuperblockCloner));
+ SearchForSubgraphExits(&exits);
+
+ // The only loops with live-outs which are currently supported are loops with a single exit.
+ if (!live_outs.empty() && exits.size() != 1) {
+ return false;
}
return true;
@@ -794,8 +895,10 @@
DumpInputSets();
}
+ CollectLiveOutsAndCheckClonable(&live_outs_);
// Find an area in the graph for which control flow information should be adjusted.
FindAndSetLocalAreaForAdjustments();
+ ConstructSubgraphClosedSSA();
// Clone the basic blocks from the orig_bb_set_; data flow is invalid after the call and is to be
// adjusted.
CloneBasicBlocks();
@@ -819,6 +922,7 @@
AdjustControlFlowInfo();
// Fix data flow of the graph.
ResolveDataFlow();
+ FixSubgraphClosedSSAAfterCloning();
}
void SuperblockCloner::CleanUp() {
@@ -985,8 +1089,14 @@
HBasicBlock* loop_header = loop_info_->GetHeader();
// Check that loop info is up-to-date.
DCHECK(loop_info_ == loop_header->GetLoopInformation());
-
HGraph* graph = loop_header->GetGraph();
+
+ if (kSuperblockClonerLogging) {
+ std::cout << "Method: " << graph->PrettyMethod() << std::endl;
+ std::cout << "Scalar loop " << (to_unroll ? "unrolling" : "peeling") <<
+ " was applied to the loop <" << loop_header->GetBlockId() << ">." << std::endl;
+ }
+
ArenaAllocator allocator(graph->GetAllocator()->GetArenaPool());
HEdgeSet remap_orig_internal(graph->GetAllocator()->Adapter(kArenaAllocSuperblockCloner));
diff --git a/compiler/optimizing/superblock_cloner.h b/compiler/optimizing/superblock_cloner.h
index e093167..f211721 100644
--- a/compiler/optimizing/superblock_cloner.h
+++ b/compiler/optimizing/superblock_cloner.h
@@ -218,7 +218,7 @@
private:
// Fills the 'exits' vector with the subgraph exits.
- void SearchForSubgraphExits(ArenaVector<HBasicBlock*>* exits);
+ void SearchForSubgraphExits(ArenaVector<HBasicBlock*>* exits) const;
// Finds and records information about the area in the graph for which control flow (back edges,
// loops, dominators) needs to be adjusted.
@@ -240,6 +240,33 @@
void ResolveDataFlow();
//
+ // Helpers for live-outs processing and Subgraph-closed SSA.
+ //
+ // - live-outs - values which are defined inside the subgraph and have uses outside.
+ // - Subgraph-closed SSA - SSA form for which all the values defined inside the subgraph
+ // have no outside uses except for the phi-nodes in the subgraph exits.
+ //
+ // Note: now if the subgraph has live-outs it is only clonable if it has a single exit; this
+ // makes the subgraph-closed SSA form construction much easier.
+ //
+ // TODO: Support subgraphs with live-outs and multiple exits.
+ //
+
+ // For each live-out value 'val' in the region puts a record <val, val> into the map.
+ // Returns whether all of the instructions in the subgraph are clonable.
+ bool CollectLiveOutsAndCheckClonable(HInstructionMap* live_outs_) const;
+
+ // Constructs Subgraph-closed SSA; precondition - a subgraph has a single exit.
+ //
+ // For each live-out 'val' in 'live_outs_' map inserts a HPhi 'phi' into the exit node, updates
+ // the record in the map to <val, phi> and replaces all outside uses with this phi.
+ void ConstructSubgraphClosedSSA();
+
+ // Fixes the data flow for the live-out 'val' by adding a 'copy_val' input to the corresponding
+ // (<val, phi>) phi after the cloning is done.
+ void FixSubgraphClosedSSAAfterCloning();
+
+ //
// Helpers for CloneBasicBlock.
//
@@ -316,6 +343,8 @@
HLoopInformation* outer_loop_;
HBasicBlockSet outer_loop_bb_set_;
+ HInstructionMap live_outs_;
+
ART_FRIEND_TEST(SuperblockClonerTest, AdjustControlFlowInfo);
ART_FRIEND_TEST(SuperblockClonerTest, IsGraphConnected);