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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#if !defined(DART_PRECOMPILED_RUNTIME)
#include "vm/compiler/backend/flow_graph.h"
#include "vm/bit_vector.h"
#include "vm/compiler/backend/flow_graph_compiler.h"
#include "vm/compiler/backend/il.h"
#include "vm/compiler/backend/il_printer.h"
#include "vm/compiler/backend/loops.h"
#include "vm/compiler/backend/range_analysis.h"
#include "vm/compiler/cha.h"
#include "vm/compiler/compiler_state.h"
#include "vm/compiler/frontend/flow_graph_builder.h"
#include "vm/growable_array.h"
#include "vm/object_store.h"
#include "vm/resolver.h"
namespace dart {
#if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_IA32)
// Smi->Int32 widening pass is disabled due to dartbug.com/32619.
DEFINE_FLAG(bool, use_smi_widening, false, "Enable Smi->Int32 widening pass.");
DEFINE_FLAG(bool, trace_smi_widening, false, "Trace Smi->Int32 widening pass.");
#endif
DEFINE_FLAG(bool, prune_dead_locals, true, "optimize dead locals away");
DECLARE_FLAG(bool, verify_compiler);
// Quick access to the current zone.
#define Z (zone())
FlowGraph::FlowGraph(const ParsedFunction& parsed_function,
GraphEntryInstr* graph_entry,
intptr_t max_block_id,
PrologueInfo prologue_info)
: thread_(Thread::Current()),
parent_(),
current_ssa_temp_index_(0),
max_block_id_(max_block_id),
parsed_function_(parsed_function),
num_direct_parameters_(parsed_function.function().HasOptionalParameters()
? 0
: parsed_function.function().NumParameters()),
graph_entry_(graph_entry),
preorder_(),
postorder_(),
reverse_postorder_(),
optimized_block_order_(),
constant_null_(nullptr),
constant_dead_(nullptr),
licm_allowed_(true),
prologue_info_(prologue_info),
loop_hierarchy_(nullptr),
loop_invariant_loads_(nullptr),
deferred_prefixes_(parsed_function.deferred_prefixes()),
await_token_positions_(nullptr),
captured_parameters_(new (zone()) BitVector(zone(), variable_count())),
inlining_id_(-1),
should_print_(FlowGraphPrinter::ShouldPrint(parsed_function.function())) {
DiscoverBlocks();
}
void FlowGraph::EnsureSSATempIndex(Definition* defn, Definition* replacement) {
if ((replacement->ssa_temp_index() == -1) && (defn->ssa_temp_index() != -1)) {
AllocateSSAIndexes(replacement);
}
}
void FlowGraph::ReplaceCurrentInstruction(ForwardInstructionIterator* iterator,
Instruction* current,
Instruction* replacement) {
Definition* current_defn = current->AsDefinition();
if ((replacement != NULL) && (current_defn != NULL)) {
Definition* replacement_defn = replacement->AsDefinition();
ASSERT(replacement_defn != NULL);
current_defn->ReplaceUsesWith(replacement_defn);
EnsureSSATempIndex(current_defn, replacement_defn);
if (FLAG_trace_optimization) {
THR_Print("Replacing v%" Pd " with v%" Pd "\n",
current_defn->ssa_temp_index(),
replacement_defn->ssa_temp_index());
}
} else if (FLAG_trace_optimization) {
if (current_defn == NULL) {
THR_Print("Removing %s\n", current->DebugName());
} else {
ASSERT(!current_defn->HasUses());
THR_Print("Removing v%" Pd ".\n", current_defn->ssa_temp_index());
}
}
if (current->ArgumentCount() != 0) {
// Replacing a call instruction with something else. Must remove
// superfluous push arguments.
for (intptr_t i = 0; i < current->ArgumentCount(); ++i) {
PushArgumentInstr* push = current->PushArgumentAt(i);
if (replacement == NULL || i >= replacement->ArgumentCount() ||
replacement->PushArgumentAt(i) != push) {
push->ReplaceUsesWith(push->value()->definition());
push->RemoveFromGraph();
}
}
}
iterator->RemoveCurrentFromGraph();
}
void FlowGraph::AddToDeferredPrefixes(
ZoneGrowableArray<const LibraryPrefix*>* from) {
ZoneGrowableArray<const LibraryPrefix*>* to = deferred_prefixes();
for (intptr_t i = 0; i < from->length(); i++) {
const LibraryPrefix* prefix = (*from)[i];
for (intptr_t j = 0; j < to->length(); j++) {
if ((*to)[j]->raw() == prefix->raw()) {
return;
}
}
to->Add(prefix);
}
}
bool FlowGraph::ShouldReorderBlocks(const Function& function,
bool is_optimized) {
return is_optimized && FLAG_reorder_basic_blocks &&
!function.is_intrinsic() && !function.IsFfiTrampoline();
}
GrowableArray<BlockEntryInstr*>* FlowGraph::CodegenBlockOrder(
bool is_optimized) {
return ShouldReorderBlocks(function(), is_optimized) ? &optimized_block_order_
: &reverse_postorder_;
}
ConstantInstr* FlowGraph::GetConstant(const Object& object) {
ConstantInstr* constant = constant_instr_pool_.LookupValue(object);
if (constant == NULL) {
// Otherwise, allocate and add it to the pool.
constant =
new (zone()) ConstantInstr(Object::ZoneHandle(zone(), object.raw()));
constant->set_ssa_temp_index(alloc_ssa_temp_index());
AddToGraphInitialDefinitions(constant);
constant_instr_pool_.Insert(constant);
}
return constant;
}
void FlowGraph::AddToGraphInitialDefinitions(Definition* defn) {
defn->set_previous(graph_entry_);
graph_entry_->initial_definitions()->Add(defn);
}
void FlowGraph::AddToInitialDefinitions(BlockEntryWithInitialDefs* entry,
Definition* defn) {
defn->set_previous(entry);
entry->initial_definitions()->Add(defn);
}
void FlowGraph::InsertBefore(Instruction* next,
Instruction* instr,
Environment* env,
UseKind use_kind) {
InsertAfter(next->previous(), instr, env, use_kind);
}
void FlowGraph::InsertAfter(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
if (use_kind == kValue) {
ASSERT(instr->IsDefinition());
AllocateSSAIndexes(instr->AsDefinition());
}
instr->InsertAfter(prev);
ASSERT(instr->env() == NULL);
if (env != NULL) {
env->DeepCopyTo(zone(), instr);
}
}
Instruction* FlowGraph::AppendTo(Instruction* prev,
Instruction* instr,
Environment* env,
UseKind use_kind) {
if (use_kind == kValue) {
ASSERT(instr->IsDefinition());
AllocateSSAIndexes(instr->AsDefinition());
}
ASSERT(instr->env() == NULL);
if (env != NULL) {
env->DeepCopyTo(zone(), instr);
}
return prev->AppendInstruction(instr);
}
// A wrapper around block entries including an index of the next successor to
// be read.
class BlockTraversalState {
public:
explicit BlockTraversalState(BlockEntryInstr* block)
: block_(block),
next_successor_ix_(block->last_instruction()->SuccessorCount() - 1) {}
bool HasNextSuccessor() const { return next_successor_ix_ >= 0; }
BlockEntryInstr* NextSuccessor() {
ASSERT(HasNextSuccessor());
return block_->last_instruction()->SuccessorAt(next_successor_ix_--);
}
BlockEntryInstr* block() const { return block_; }
private:
BlockEntryInstr* block_;
intptr_t next_successor_ix_;
DISALLOW_ALLOCATION();
};
void FlowGraph::DiscoverBlocks() {
StackZone zone(thread());
// Initialize state.
preorder_.Clear();
postorder_.Clear();
reverse_postorder_.Clear();
parent_.Clear();
GrowableArray<BlockTraversalState> block_stack;
graph_entry_->DiscoverBlock(NULL, &preorder_, &parent_);
block_stack.Add(BlockTraversalState(graph_entry_));
while (!block_stack.is_empty()) {
BlockTraversalState& state = block_stack.Last();
BlockEntryInstr* block = state.block();
if (state.HasNextSuccessor()) {
// Process successors one-by-one.
BlockEntryInstr* succ = state.NextSuccessor();
if (succ->DiscoverBlock(block, &preorder_, &parent_)) {
block_stack.Add(BlockTraversalState(succ));
}
} else {
// All successors have been processed, pop the current block entry node
// and add it to the postorder list.
block_stack.RemoveLast();
block->set_postorder_number(postorder_.length());
postorder_.Add(block);
}
}
ASSERT(postorder_.length() == preorder_.length());
// Create an array of blocks in reverse postorder.
intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; ++i) {
reverse_postorder_.Add(postorder_[block_count - i - 1]);
}
ResetLoopHierarchy();
}
void FlowGraph::MergeBlocks() {
bool changed = false;
BitVector* merged = new (zone()) BitVector(zone(), postorder().length());
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
BlockEntryInstr* block = block_it.Current();
if (block->IsGraphEntry()) continue;
if (merged->Contains(block->postorder_number())) continue;
Instruction* last = block->last_instruction();
BlockEntryInstr* successor = NULL;
while ((!last->IsIndirectGoto()) && (last->SuccessorCount() == 1) &&
(!last->SuccessorAt(0)->IsIndirectEntry()) &&
(last->SuccessorAt(0)->PredecessorCount() == 1) &&
(block->try_index() == last->SuccessorAt(0)->try_index())) {
successor = last->SuccessorAt(0);
ASSERT(last->IsGoto());
// Remove environment uses and unlink goto and block entry.
successor->UnuseAllInputs();
last->previous()->LinkTo(successor->next());
last->UnuseAllInputs();
last = successor->last_instruction();
merged->Add(successor->postorder_number());
changed = true;
if (FLAG_trace_optimization) {
THR_Print("Merged blocks B%" Pd " and B%" Pd "\n", block->block_id(),
successor->block_id());
}
}
// The new block inherits the block id of the last successor to maintain
// the order of phi inputs at its successors consistent with block ids.
if (successor != NULL) {
block->set_block_id(successor->block_id());
}
}
// Recompute block order after changes were made.
if (changed) DiscoverBlocks();
}
// Debugging code to verify the construction of use lists.
static intptr_t MembershipCount(Value* use, Value* list) {
intptr_t count = 0;
while (list != NULL) {
if (list == use) ++count;
list = list->next_use();
}
return count;
}
static void VerifyUseListsInInstruction(Instruction* instr) {
ASSERT(instr != NULL);
ASSERT(!instr->IsJoinEntry());
for (intptr_t i = 0; i < instr->InputCount(); ++i) {
Value* use = instr->InputAt(i);
ASSERT(use->definition() != NULL);
ASSERT((use->definition() != instr) || use->definition()->IsPhi() ||
use->definition()->IsMaterializeObject());
ASSERT(use->instruction() == instr);
ASSERT(use->use_index() == i);
ASSERT(!FLAG_verify_compiler ||
(1 == MembershipCount(use, use->definition()->input_use_list())));
}
if (instr->env() != NULL) {
intptr_t use_index = 0;
for (Environment::DeepIterator it(instr->env()); !it.Done(); it.Advance()) {
Value* use = it.CurrentValue();
ASSERT(use->definition() != NULL);
ASSERT((use->definition() != instr) || use->definition()->IsPhi());
ASSERT(use->instruction() == instr);
ASSERT(use->use_index() == use_index++);
ASSERT(!FLAG_verify_compiler ||
(1 == MembershipCount(use, use->definition()->env_use_list())));
}
}
Definition* defn = instr->AsDefinition();
if (defn != NULL) {
// Used definitions must have an SSA name. We use the name to index
// into bit vectors during analyses. Some definitions without SSA names
// (e.g., PushArgument) have environment uses.
ASSERT((defn->input_use_list() == NULL) || defn->HasSSATemp());
Value* prev = NULL;
Value* curr = defn->input_use_list();
while (curr != NULL) {
ASSERT(prev == curr->previous_use());
ASSERT(defn == curr->definition());
Instruction* instr = curr->instruction();
// The instruction should not be removed from the graph.
ASSERT((instr->IsPhi() && instr->AsPhi()->is_alive()) ||
(instr->previous() != NULL));
ASSERT(curr == instr->InputAt(curr->use_index()));
prev = curr;
curr = curr->next_use();
}
prev = NULL;
curr = defn->env_use_list();
while (curr != NULL) {
ASSERT(prev == curr->previous_use());
ASSERT(defn == curr->definition());
Instruction* instr = curr->instruction();
ASSERT(curr == instr->env()->ValueAtUseIndex(curr->use_index()));
// BlockEntry instructions have environments attached to them but
// have no reliable way to verify if they are still in the graph.
// Thus we just assume they are.
ASSERT(instr->IsBlockEntry() ||
(instr->IsPhi() && instr->AsPhi()->is_alive()) ||
(instr->previous() != NULL));
prev = curr;
curr = curr->next_use();
}
}
}
void FlowGraph::ComputeIsReceiverRecursive(
PhiInstr* phi,
GrowableArray<PhiInstr*>* unmark) const {
if (phi->is_receiver() != PhiInstr::kUnknownReceiver) return;
phi->set_is_receiver(PhiInstr::kReceiver);
for (intptr_t i = 0; i < phi->InputCount(); ++i) {
Definition* def = phi->InputAt(i)->definition();
if (def->IsParameter() && (def->AsParameter()->index() == 0)) continue;
if (!def->IsPhi()) {
phi->set_is_receiver(PhiInstr::kNotReceiver);
break;
}
ComputeIsReceiverRecursive(def->AsPhi(), unmark);
if (def->AsPhi()->is_receiver() == PhiInstr::kNotReceiver) {
phi->set_is_receiver(PhiInstr::kNotReceiver);
break;
}
}
if (phi->is_receiver() == PhiInstr::kNotReceiver) {
unmark->Add(phi);
}
}
void FlowGraph::ComputeIsReceiver(PhiInstr* phi) const {
GrowableArray<PhiInstr*> unmark;
ComputeIsReceiverRecursive(phi, &unmark);
// Now drain unmark.
while (!unmark.is_empty()) {
PhiInstr* phi = unmark.RemoveLast();
for (Value::Iterator it(phi->input_use_list()); !it.Done(); it.Advance()) {
PhiInstr* use = it.Current()->instruction()->AsPhi();
if ((use != NULL) && (use->is_receiver() == PhiInstr::kReceiver)) {
use->set_is_receiver(PhiInstr::kNotReceiver);
unmark.Add(use);
}
}
}
}
bool FlowGraph::IsReceiver(Definition* def) const {
def = def->OriginalDefinition(); // Could be redefined.
if (def->IsParameter()) return (def->AsParameter()->index() == 0);
if (!def->IsPhi() || graph_entry()->HasSingleEntryPoint()) {
return false;
}
PhiInstr* phi = def->AsPhi();
if (phi->is_receiver() != PhiInstr::kUnknownReceiver) {
return (phi->is_receiver() == PhiInstr::kReceiver);
}
// Not known if this phi is the receiver yet. Compute it now.
ComputeIsReceiver(phi);
return (phi->is_receiver() == PhiInstr::kReceiver);
}
FlowGraph::ToCheck FlowGraph::CheckForInstanceCall(
InstanceCallInstr* call,
RawFunction::Kind kind) const {
if (!FLAG_use_cha_deopt && !isolate()->all_classes_finalized()) {
// Even if class or function are private, lazy class finalization
// may later add overriding methods.
return ToCheck::kCheckCid;
}
// Best effort to get the receiver class.
Value* receiver = call->Receiver();
Class& receiver_class = Class::Handle(zone());
bool receiver_maybe_null = false;
if (function().IsDynamicFunction() && IsReceiver(receiver->definition())) {
// Call receiver is callee receiver: calling "this.g()" in f().
receiver_class = function().Owner();
} else if (isolate()->can_use_strong_mode_types()) {
// In strong mode, get the receiver's compile type. Note that
// we allow nullable types, which may result in just generating
// a null check rather than the more elaborate class check
CompileType* type = receiver->Type();
const AbstractType* atype = type->ToAbstractType();
if (atype->IsInstantiated() && atype->HasTypeClass() &&
!atype->IsDynamicType()) {
if (type->is_nullable()) {
receiver_maybe_null = true;
}
receiver_class = atype->type_class();
if (receiver_class.is_implemented()) {
receiver_class = Class::null();
}
}
}
// Useful receiver class information?
if (receiver_class.IsNull()) {
return ToCheck::kCheckCid;
} else if (call->HasICData()) {
// If the static class type does not match information found in ICData
// (which may be "guessed"), then bail, since subsequent code generation
// (AOT and JIT) for inlining uses the latter.
// TODO(ajcbik): improve this by using the static class.
const intptr_t cid = receiver_class.id();
const ICData* data = call->ic_data();
bool match = false;
Class& cls = Class::Handle(zone());
Function& fun = Function::Handle(zone());
for (intptr_t i = 0, len = data->NumberOfChecks(); i < len; i++) {
fun = data->GetTargetAt(i);
cls = fun.Owner();
if (data->GetReceiverClassIdAt(i) == cid || cls.id() == cid) {
match = true;
break;
}
}
if (!match) {
return ToCheck::kCheckCid;
}
}
const String& method_name =
(kind == RawFunction::kMethodExtractor)
? String::Handle(zone(), Field::NameFromGetter(call->function_name()))
: call->function_name();
// If the receiver can have the null value, exclude any method
// that is actually valid on a null receiver.
if (receiver_maybe_null) {
#ifdef TARGET_ARCH_DBC
// TODO(ajcbik): DBC does not support null check at all yet.
return ToCheck::kCheckCid;
#else
const Class& null_class =
Class::Handle(zone(), isolate()->object_store()->null_class());
const Function& target = Function::Handle(
zone(),
Resolver::ResolveDynamicAnyArgs(zone(), null_class, method_name));
if (!target.IsNull()) {
return ToCheck::kCheckCid;
}
#endif
}
// Use CHA to determine if the method is not overridden by any subclass
// of the receiver class. Any methods that are valid when the receiver
// has a null value are excluded above (to avoid throwing an exception
// on something valid, like null.hashCode).
intptr_t subclass_count = 0;
CHA& cha = thread()->compiler_state().cha();
if (!cha.HasOverride(receiver_class, method_name, &subclass_count)) {
if (FLAG_trace_cha) {
THR_Print(
" **(CHA) Instance call needs no class check since there "
"are no overrides of method '%s' on '%s'\n",
method_name.ToCString(), receiver_class.ToCString());
}
if (FLAG_use_cha_deopt) {
cha.AddToGuardedClasses(receiver_class, subclass_count);
}
return receiver_maybe_null ? ToCheck::kCheckNull : ToCheck::kNoCheck;
}
return ToCheck::kCheckCid;
}
Instruction* FlowGraph::CreateCheckClass(Definition* to_check,
const Cids& cids,
intptr_t deopt_id,
TokenPosition token_pos) {
if (cids.IsMonomorphic() && cids.MonomorphicReceiverCid() == kSmiCid) {
return new (zone())
CheckSmiInstr(new (zone()) Value(to_check), deopt_id, token_pos);
}
return new (zone())
CheckClassInstr(new (zone()) Value(to_check), deopt_id, cids, token_pos);
}
Definition* FlowGraph::CreateCheckBound(Definition* length,
Definition* index,
intptr_t deopt_id) {
Value* val1 = new (zone()) Value(length);
Value* val2 = new (zone()) Value(index);
if (FLAG_precompiled_mode) {
return new (zone()) GenericCheckBoundInstr(val1, val2, deopt_id);
}
return new (zone()) CheckArrayBoundInstr(val1, val2, deopt_id);
}
void FlowGraph::AddExactnessGuard(InstanceCallInstr* call,
intptr_t receiver_cid) {
const Class& cls = Class::Handle(
zone(), Isolate::Current()->class_table()->At(receiver_cid));
Definition* load_type_args = new (zone()) LoadFieldInstr(
call->Receiver()->CopyWithType(),
Slot::GetTypeArgumentsSlotFor(thread(), cls), call->token_pos());
InsertBefore(call, load_type_args, call->env(), FlowGraph::kValue);
const AbstractType& type =
AbstractType::Handle(zone(), call->ic_data()->StaticReceiverType());
ASSERT(!type.IsNull());
const TypeArguments& args = TypeArguments::Handle(zone(), type.arguments());
Instruction* guard = new (zone()) CheckConditionInstr(
new StrictCompareInstr(call->token_pos(), Token::kEQ_STRICT,
new (zone()) Value(load_type_args),
new (zone()) Value(GetConstant(args)),
/*needs_number_check=*/false, call->deopt_id()),
call->deopt_id());
InsertBefore(call, guard, call->env(), FlowGraph::kEffect);
}
bool FlowGraph::VerifyUseLists() {
// Verify the initial definitions.
for (intptr_t i = 0; i < graph_entry_->initial_definitions()->length(); ++i) {
VerifyUseListsInInstruction((*graph_entry_->initial_definitions())[i]);
}
// Verify phis in join entries and the instructions in each block.
for (intptr_t i = 0; i < preorder_.length(); ++i) {
BlockEntryInstr* entry = preorder_[i];
JoinEntryInstr* join = entry->AsJoinEntry();
if (join != NULL) {
for (PhiIterator it(join); !it.Done(); it.Advance()) {
PhiInstr* phi = it.Current();
ASSERT(phi != NULL);
VerifyUseListsInInstruction(phi);
}
}
for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
VerifyUseListsInInstruction(it.Current());
}
}
return true; // Return true so we can ASSERT validation.
}
// Verify that a redefinition dominates all uses of the redefined value.
bool FlowGraph::VerifyRedefinitions() {
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
for (ForwardInstructionIterator instr_it(block_it.Current());
!instr_it.Done(); instr_it.Advance()) {
RedefinitionInstr* redefinition = instr_it.Current()->AsRedefinition();
if (redefinition != NULL) {
Definition* original = redefinition->value()->definition();
for (Value::Iterator it(original->input_use_list()); !it.Done();
it.Advance()) {
Value* original_use = it.Current();
if (original_use->instruction() == redefinition) {
continue;
}
if (original_use->instruction()->IsDominatedBy(redefinition)) {
FlowGraphPrinter::PrintGraph("VerifyRedefinitions", this);
THR_Print("%s\n", redefinition->ToCString());
THR_Print("use=%s\n", original_use->instruction()->ToCString());
return false;
}
}
}
}
}
return true;
}
LivenessAnalysis::LivenessAnalysis(
intptr_t variable_count,
const GrowableArray<BlockEntryInstr*>& postorder)
: zone_(Thread::Current()->zone()),
variable_count_(variable_count),
postorder_(postorder),
live_out_(postorder.length()),
kill_(postorder.length()),
live_in_(postorder.length()) {}
bool LivenessAnalysis::UpdateLiveOut(const BlockEntryInstr& block) {
BitVector* live_out = live_out_[block.postorder_number()];
bool changed = false;
Instruction* last = block.last_instruction();
ASSERT(last != NULL);
for (intptr_t i = 0; i < last->SuccessorCount(); i++) {
BlockEntryInstr* succ = last->SuccessorAt(i);
ASSERT(succ != NULL);
if (live_out->AddAll(live_in_[succ->postorder_number()])) {
changed = true;
}
}
return changed;
}
bool LivenessAnalysis::UpdateLiveIn(const BlockEntryInstr& block) {
BitVector* live_out = live_out_[block.postorder_number()];
BitVector* kill = kill_[block.postorder_number()];
BitVector* live_in = live_in_[block.postorder_number()];
return live_in->KillAndAdd(kill, live_out);
}
void LivenessAnalysis::ComputeLiveInAndLiveOutSets() {
const intptr_t block_count = postorder_.length();
bool changed;
do {
changed = false;
for (intptr_t i = 0; i < block_count; i++) {
const BlockEntryInstr& block = *postorder_[i];
// Live-in set depends only on kill set which does not
// change in this loop and live-out set. If live-out
// set does not change there is no need to recompute
// live-in set.
if (UpdateLiveOut(block) && UpdateLiveIn(block)) {
changed = true;
}
}
} while (changed);
}
void LivenessAnalysis::Analyze() {
const intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; i++) {
live_out_.Add(new (zone()) BitVector(zone(), variable_count_));
kill_.Add(new (zone()) BitVector(zone(), variable_count_));
live_in_.Add(new (zone()) BitVector(zone(), variable_count_));
}
ComputeInitialSets();
ComputeLiveInAndLiveOutSets();
}
static void PrintBitVector(const char* tag, BitVector* v) {
THR_Print("%s:", tag);
for (BitVector::Iterator it(v); !it.Done(); it.Advance()) {
THR_Print(" %" Pd "", it.Current());
}
THR_Print("\n");
}
void LivenessAnalysis::Dump() {
const intptr_t block_count = postorder_.length();
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = postorder_[i];
THR_Print("block @%" Pd " -> ", block->block_id());
Instruction* last = block->last_instruction();
for (intptr_t j = 0; j < last->SuccessorCount(); j++) {
BlockEntryInstr* succ = last->SuccessorAt(j);
THR_Print(" @%" Pd "", succ->block_id());
}
THR_Print("\n");
PrintBitVector(" live out", live_out_[i]);
PrintBitVector(" kill", kill_[i]);
PrintBitVector(" live in", live_in_[i]);
}
}
// Computes liveness information for local variables.
class VariableLivenessAnalysis : public LivenessAnalysis {
public:
explicit VariableLivenessAnalysis(FlowGraph* flow_graph)
: LivenessAnalysis(flow_graph->variable_count(), flow_graph->postorder()),
flow_graph_(flow_graph),
assigned_vars_() {}
// For every block (in preorder) compute and return set of variables that
// have new assigned values flowing out of that block.
const GrowableArray<BitVector*>& ComputeAssignedVars() {
// We can't directly return kill_ because it uses postorder numbering while
// SSA construction uses preorder numbering internally.
// We have to permute postorder into preorder.
assigned_vars_.Clear();
const intptr_t block_count = flow_graph_->preorder().length();
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = flow_graph_->preorder()[i];
// All locals are assigned inside a try{} block.
// This is a safe approximation and workaround to force insertion of
// phis for stores that appear non-live because of the way catch-blocks
// are connected to the graph: They normally are dominated by the
// try-entry, but are direct successors of the graph entry in our flow
// graph.
// TODO(fschneider): Improve this approximation by better modeling the
// actual data flow to reduce the number of redundant phis.
BitVector* kill = GetKillSet(block);
if (block->InsideTryBlock()) {
kill->SetAll();
} else {
kill->Intersect(GetLiveOutSet(block));
}
assigned_vars_.Add(kill);
}
return assigned_vars_;
}
// Returns true if the value set by the given store reaches any load from the
// same local variable.
bool IsStoreAlive(BlockEntryInstr* block, StoreLocalInstr* store) {
if (store->local().Equals(*flow_graph_->CurrentContextVar())) {
return true;
}
if (store->is_dead()) {
return false;
}
if (store->is_last()) {
const intptr_t index = flow_graph_->EnvIndex(&store->local());
return GetLiveOutSet(block)->Contains(index);
}
return true;
}
// Returns true if the given load is the last for the local and the value
// of the local will not flow into another one.
bool IsLastLoad(BlockEntryInstr* block, LoadLocalInstr* load) {
if (load->local().Equals(*flow_graph_->CurrentContextVar())) {
return false;
}
const intptr_t index = flow_graph_->EnvIndex(&load->local());
return load->is_last() && !GetLiveOutSet(block)->Contains(index);
}
private:
virtual void ComputeInitialSets();
const FlowGraph* flow_graph_;
GrowableArray<BitVector*> assigned_vars_;
};
void VariableLivenessAnalysis::ComputeInitialSets() {
const intptr_t block_count = postorder_.length();
BitVector* last_loads = new (zone()) BitVector(zone(), variable_count_);
for (intptr_t i = 0; i < block_count; i++) {
BlockEntryInstr* block = postorder_[i];
BitVector* kill = kill_[i];
BitVector* live_in = live_in_[i];
last_loads->Clear();
// There is an implicit use (load-local) of every local variable at each
// call inside a try{} block and every call has an implicit control-flow
// to the catch entry. As an approximation we mark all locals as live
// inside try{}.
// TODO(fschneider): Improve this approximation, since not all local
// variable stores actually reach a call.
if (block->InsideTryBlock()) {
live_in->SetAll();
continue;
}
// Iterate backwards starting at the last instruction.
for (BackwardInstructionIterator it(block); !it.Done(); it.Advance()) {
Instruction* current = it.Current();
LoadLocalInstr* load = current->AsLoadLocal();
if (load != NULL) {
const intptr_t index = flow_graph_->EnvIndex(&load->local());
if (index >= live_in->length()) continue; // Skip tmp_locals.
live_in->Add(index);
if (!last_loads->Contains(index)) {
last_loads->Add(index);
load->mark_last();
}
continue;
}
StoreLocalInstr* store = current->AsStoreLocal();
if (store != NULL) {
const intptr_t index = flow_graph_->EnvIndex(&store->local());
if (index >= live_in->length()) continue; // Skip tmp_locals.
if (kill->Contains(index)) {
if (!live_in->Contains(index)) {
store->mark_dead();
}
} else {
if (!live_in->Contains(index)) {
store->mark_last();
}
kill->Add(index);
}
live_in->Remove(index);
continue;
}
}
// For blocks with parameter or special parameter instructions we add them
// to the kill set.
const bool is_function_entry = block->IsFunctionEntry();
const bool is_osr_entry = block->IsOsrEntry();
if (is_function_entry || is_osr_entry || block->IsCatchBlockEntry()) {
const intptr_t parameter_count =
is_osr_entry ? flow_graph_->variable_count()
: flow_graph_->num_direct_parameters();
for (intptr_t i = 0; i < parameter_count; ++i) {
live_in->Remove(i);
kill->Add(i);
}
}
if (is_function_entry) {
if (flow_graph_->parsed_function().has_arg_desc_var()) {
const auto index = flow_graph_->ArgumentDescriptorEnvIndex();
live_in->Remove(index);
kill->Add(index);
}
}
}
}
void FlowGraph::ComputeSSA(
intptr_t next_virtual_register_number,
ZoneGrowableArray<Definition*>* inlining_parameters) {
ASSERT((next_virtual_register_number == 0) || (inlining_parameters != NULL));
current_ssa_temp_index_ = next_virtual_register_number;
GrowableArray<BitVector*> dominance_frontier;
GrowableArray<intptr_t> idom;
ComputeDominators(&dominance_frontier);
VariableLivenessAnalysis variable_liveness(this);
variable_liveness.Analyze();
GrowableArray<PhiInstr*> live_phis;
InsertPhis(preorder_, variable_liveness.ComputeAssignedVars(),
dominance_frontier, &live_phis);
// Rename uses to reference inserted phis where appropriate.
// Collect phis that reach a non-environment use.
Rename(&live_phis, &variable_liveness, inlining_parameters);
// Propagate alive mark transitively from alive phis and then remove
// non-live ones.
RemoveDeadPhis(&live_phis);
}
// Compute immediate dominators and the dominance frontier for each basic
// block. As a side effect of the algorithm, sets the immediate dominator
// of each basic block.
//
// dominance_frontier: an output parameter encoding the dominance frontier.
// The array maps the preorder block number of a block to the set of
// (preorder block numbers of) blocks in the dominance frontier.
void FlowGraph::ComputeDominators(
GrowableArray<BitVector*>* dominance_frontier) {
// Use the SEMI-NCA algorithm to compute dominators. This is a two-pass
// version of the Lengauer-Tarjan algorithm (LT is normally three passes)
// that eliminates a pass by using nearest-common ancestor (NCA) to
// compute immediate dominators from semidominators. It also removes a
// level of indirection in the link-eval forest data structure.
//
// The algorithm is described in Georgiadis, Tarjan, and Werneck's
// "Finding Dominators in Practice".
// See http://www.cs.princeton.edu/~rwerneck/dominators/ .
// All arrays are maps between preorder basic-block numbers.
intptr_t size = parent_.length();
GrowableArray<intptr_t> idom(size); // Immediate dominator.
GrowableArray<intptr_t> semi(size); // Semidominator.
GrowableArray<intptr_t> label(size); // Label for link-eval forest.
// 1. First pass: compute semidominators as in Lengauer-Tarjan.
// Semidominators are computed from a depth-first spanning tree and are an
// approximation of immediate dominators.
// Use a link-eval data structure with path compression. Implement path
// compression in place by mutating the parent array. Each block has a
// label, which is the minimum block number on the compressed path.
// Initialize idom, semi, and label used by SEMI-NCA. Initialize the
// dominance frontier output array.
for (intptr_t i = 0; i < size; ++i) {
idom.Add(parent_[i]);
semi.Add(i);
label.Add(i);
dominance_frontier->Add(new (zone()) BitVector(zone(), size));
}
// Loop over the blocks in reverse preorder (not including the graph
// entry). Clear the dominated blocks in the graph entry in case
// ComputeDominators is used to recompute them.
preorder_[0]->ClearDominatedBlocks();
for (intptr_t block_index = size - 1; block_index >= 1; --block_index) {
// Loop over the predecessors.
BlockEntryInstr* block = preorder_[block_index];
// Clear the immediately dominated blocks in case ComputeDominators is
// used to recompute them.
block->ClearDominatedBlocks();
for (intptr_t i = 0, count = block->PredecessorCount(); i < count; ++i) {
BlockEntryInstr* pred = block->PredecessorAt(i);
ASSERT(pred != NULL);
// Look for the semidominator by ascending the semidominator path
// starting from pred.
intptr_t pred_index = pred->preorder_number();
intptr_t best = pred_index;
if (pred_index > block_index) {
CompressPath(block_index, pred_index, &parent_, &label);
best = label[pred_index];
}
// Update the semidominator if we've found a better one.
semi[block_index] = Utils::Minimum(semi[block_index], semi[best]);
}
// Now use label for the semidominator.
label[block_index] = semi[block_index];
}
// 2. Compute the immediate dominators as the nearest common ancestor of
// spanning tree parent and semidominator, for all blocks except the entry.
for (intptr_t block_index = 1; block_index < size; ++block_index) {
intptr_t dom_index = idom[block_index];
while (dom_index > semi[block_index]) {
dom_index = idom[dom_index];
}
idom[block_index] = dom_index;
preorder_[dom_index]->AddDominatedBlock(preorder_[block_index]);
}
// 3. Now compute the dominance frontier for all blocks. This is
// algorithm in "A Simple, Fast Dominance Algorithm" (Figure 5), which is
// attributed to a paper by Ferrante et al. There is no bookkeeping
// required to avoid adding a block twice to the same block's dominance
// frontier because we use a set to represent the dominance frontier.
for (intptr_t block_index = 0; block_index < size; ++block_index) {
BlockEntryInstr* block = preorder_[block_index];
intptr_t count = block->PredecessorCount();
if (count <= 1) continue;
for (intptr_t i = 0; i < count; ++i) {
BlockEntryInstr* runner = block->PredecessorAt(i);
while (runner != block->dominator()) {
(*dominance_frontier)[runner->preorder_number()]->Add(block_index);
runner = runner->dominator();
}
}
}
}
void FlowGraph::CompressPath(intptr_t start_index,
intptr_t current_index,
GrowableArray<intptr_t>* parent,
GrowableArray<intptr_t>* label) {
intptr_t next_index = (*parent)[current_index];
if (next_index > start_index) {
CompressPath(start_index, next_index, parent, label);
(*label)[current_index] =
Utils::Minimum((*label)[current_index], (*label)[next_index]);
(*parent)[current_index] = (*parent)[next_index];
}
}
void FlowGraph::InsertPhis(const GrowableArray<BlockEntryInstr*>& preorder,
const GrowableArray<BitVector*>& assigned_vars,
const GrowableArray<BitVector*>& dom_frontier,
GrowableArray<PhiInstr*>* live_phis) {
const intptr_t block_count = preorder.length();
// Map preorder block number to the highest variable index that has a phi
// in that block. Use it to avoid inserting multiple phis for the same
// variable.
GrowableArray<intptr_t> has_already(block_count);
// Map preorder block number to the highest variable index for which the
// block went on the worklist. Use it to avoid adding the same block to
// the worklist more than once for the same variable.
GrowableArray<intptr_t> work(block_count);
// Initialize has_already and work.
for (intptr_t block_index = 0; block_index < block_count; ++block_index) {
has_already.Add(-1);
work.Add(-1);
}
// Insert phis for each variable in turn.
GrowableArray<BlockEntryInstr*> worklist;
for (intptr_t var_index = 0; var_index < variable_count(); ++var_index) {
const bool always_live =
!FLAG_prune_dead_locals || (var_index == CurrentContextEnvIndex());
// Add to the worklist each block containing an assignment.
for (intptr_t block_index = 0; block_index < block_count; ++block_index) {
if (assigned_vars[block_index]->Contains(var_index)) {
work[block_index] = var_index;
worklist.Add(preorder[block_index]);
}
}
while (!worklist.is_empty()) {
BlockEntryInstr* current = worklist.RemoveLast();
// Ensure a phi for each block in the dominance frontier of current.
for (BitVector::Iterator it(dom_frontier[current->preorder_number()]);
!it.Done(); it.Advance()) {
int index = it.Current();
if (has_already[index] < var_index) {
BlockEntryInstr* block = preorder[index];
ASSERT(block->IsJoinEntry());
PhiInstr* phi =
block->AsJoinEntry()->InsertPhi(var_index, variable_count());
if (always_live) {
phi->mark_alive();
live_phis->Add(phi);
}
has_already[index] = var_index;
if (work[index] < var_index) {
work[index] = var_index;
worklist.Add(block);
}
}
}
}
}
}
void FlowGraph::Rename(GrowableArray<PhiInstr*>* live_phis,
VariableLivenessAnalysis* variable_liveness,
ZoneGrowableArray<Definition*>* inlining_parameters) {
GraphEntryInstr* entry = graph_entry();
// Add global constants to the initial definitions.
constant_null_ = GetConstant(Object::ZoneHandle());
constant_dead_ = GetConstant(Symbols::OptimizedOut());
const intptr_t parameter_count =
IsCompiledForOsr() ? variable_count() : num_direct_parameters_;
// Initial renaming environment.
GrowableArray<Definition*> env(parameter_count + num_stack_locals());
env.FillWith(constant_dead(), 0, parameter_count);
if (!IsCompiledForOsr()) {
env.FillWith(constant_null(), parameter_count, num_stack_locals());
}
if (entry->catch_entries().length() > 0) {
// Functions with try-catch have a fixed area of stack slots reserved
// so that all local variables are stored at a known location when
// on entry to the catch.
entry->set_fixed_slot_count(num_stack_locals());
} else {
ASSERT(entry->unchecked_entry() != nullptr ? entry->SuccessorCount() == 2
: entry->SuccessorCount() == 1);
}
RenameRecursive(entry, &env, live_phis, variable_liveness,
inlining_parameters);
}
void FlowGraph::PopulateEnvironmentFromFunctionEntry(
FunctionEntryInstr* function_entry,
GrowableArray<Definition*>* env,
GrowableArray<PhiInstr*>* live_phis,
VariableLivenessAnalysis* variable_liveness,
ZoneGrowableArray<Definition*>* inlining_parameters) {
ASSERT(!IsCompiledForOsr());
const intptr_t parameter_count = num_direct_parameters_;
// Check if inlining_parameters include a type argument vector parameter.
const intptr_t inlined_type_args_param =
((inlining_parameters != NULL) && function().IsGeneric()) ? 1 : 0;
for (intptr_t i = 0; i < parameter_count; i++) {
ParameterInstr* param = new (zone()) ParameterInstr(i, function_entry);
param->set_ssa_temp_index(alloc_ssa_temp_index());
AddToInitialDefinitions(function_entry, param);
(*env)[i] = param;
}
// Override the entries in the renaming environment which are special (i.e.
// inlining arguments, type parameter, args descriptor, context, ...)
{
// Replace parameter slots with inlining definitions coming in.
if (inlining_parameters != NULL) {
for (intptr_t i = 0; i < function().NumParameters(); ++i) {
Definition* defn = (*inlining_parameters)[inlined_type_args_param + i];
AllocateSSAIndexes(defn);
AddToInitialDefinitions(function_entry, defn);
intptr_t index = EnvIndex(parsed_function_.RawParameterVariable(i));
(*env)[index] = defn;
}
}
// Replace the type arguments slot with a special parameter.
const bool reify_generic_argument = function().IsGeneric();
if (reify_generic_argument) {
ASSERT(parsed_function().function_type_arguments() != NULL);
Definition* defn;
if (inlining_parameters == NULL) {
// Note: If we are not inlining, then the prologue builder will
// take care of checking that we got the correct reified type
// arguments. This includes checking the argument descriptor in order
// to even find out if the parameter was passed or not.
defn = constant_dead();
} else {
defn = (*inlining_parameters)[0];
}
AllocateSSAIndexes(defn);
AddToInitialDefinitions(function_entry, defn);
(*env)[RawTypeArgumentEnvIndex()] = defn;
}
// Replace the argument descriptor slot with a special parameter.
if (parsed_function().has_arg_desc_var()) {
Definition* defn =
new (Z) SpecialParameterInstr(SpecialParameterInstr::kArgDescriptor,
DeoptId::kNone, function_entry);
AllocateSSAIndexes(defn);
AddToInitialDefinitions(function_entry, defn);
(*env)[ArgumentDescriptorEnvIndex()] = defn;
}
}
}
void FlowGraph::PopulateEnvironmentFromOsrEntry(
OsrEntryInstr* osr_entry,
GrowableArray<Definition*>* env) {
ASSERT(IsCompiledForOsr());
const intptr_t parameter_count = variable_count();
for (intptr_t i = 0; i < parameter_count; i++) {
ParameterInstr* param = new (zone()) ParameterInstr(i, osr_entry);
param->set_ssa_temp_index(alloc_ssa_temp_index());
AddToInitialDefinitions(osr_entry, param);
(*env)[i] = param;
}
}
void FlowGraph::PopulateEnvironmentFromCatchEntry(
CatchBlockEntryInstr* catch_entry,
GrowableArray<Definition*>* env) {
const intptr_t raw_exception_var_envindex =
catch_entry->raw_exception_var() != nullptr
? EnvIndex(catch_entry->raw_exception_var())
: -1;
const intptr_t raw_stacktrace_var_envindex =
catch_entry->raw_stacktrace_var() != nullptr
? EnvIndex(catch_entry->raw_stacktrace_var())
: -1;
// Add real definitions for all locals and parameters.
for (intptr_t i = 0; i < variable_count(); ++i) {
// Replace usages of the raw exception/stacktrace variables with
// [SpecialParameterInstr]s.
Definition* param = nullptr;
if (raw_exception_var_envindex == i) {
param = new (Z) SpecialParameterInstr(SpecialParameterInstr::kException,
DeoptId::kNone, catch_entry);
} else if (raw_stacktrace_var_envindex == i) {
param = new (Z) SpecialParameterInstr(SpecialParameterInstr::kStackTrace,
DeoptId::kNone, catch_entry);
} else {
param = new (Z) ParameterInstr(i, catch_entry);
}
param->set_ssa_temp_index(alloc_ssa_temp_index()); // New SSA temp.
(*env)[i] = param;
catch_entry->initial_definitions()->Add(param);
}
}
void FlowGraph::AttachEnvironment(Instruction* instr,
GrowableArray<Definition*>* env) {
Environment* deopt_env =
Environment::From(zone(), *env, num_direct_parameters_, parsed_function_);
if (instr->IsClosureCall()) {
deopt_env =
deopt_env->DeepCopy(zone(), deopt_env->Length() - instr->InputCount());
}
instr->SetEnvironment(deopt_env);
for (Environment::DeepIterator it(deopt_env); !it.Done(); it.Advance()) {
Value* use = it.CurrentValue();
use->definition()->AddEnvUse(use);
}
}
void FlowGraph::RenameRecursive(
BlockEntryInstr* block_entry,
GrowableArray<Definition*>* env,
GrowableArray<PhiInstr*>* live_phis,
VariableLivenessAnalysis* variable_liveness,
ZoneGrowableArray<Definition*>* inlining_parameters) {
// 1. Process phis first.
if (auto join = block_entry->AsJoinEntry()) {
if (join->phis() != NULL) {
for (intptr_t i = 0; i < join->phis()->length(); ++i) {
PhiInstr* phi = (*join->phis())[i];
if (phi != NULL) {
(*env)[i] = phi;
AllocateSSAIndexes(phi); // New SSA temp.
if (block_entry->InsideTryBlock() && !phi->is_alive()) {
// This is a safe approximation. Inside try{} all locals are
// used at every call implicitly, so we mark all phis as live
// from the start.
// TODO(fschneider): Improve this approximation to eliminate
// more redundant phis.
phi->mark_alive();
live_phis->Add(phi);
}
}
}
}
} else if (auto osr_entry = block_entry->AsOsrEntry()) {
PopulateEnvironmentFromOsrEntry(osr_entry, env);
} else if (auto function_entry = block_entry->AsFunctionEntry()) {
ASSERT(!IsCompiledForOsr());
PopulateEnvironmentFromFunctionEntry(
function_entry, env, live_phis, variable_liveness, inlining_parameters);
} else if (auto catch_entry = block_entry->AsCatchBlockEntry()) {
PopulateEnvironmentFromCatchEntry(catch_entry, env);
}
if (!block_entry->IsGraphEntry() &&
!block_entry->IsBlockEntryWithInitialDefs()) {
// Prune non-live variables at block entry by replacing their environment
// slots with null.
BitVector* live_in = variable_liveness->GetLiveInSet(block_entry);
for (intptr_t i = 0; i < variable_count(); i++) {
// TODO(fschneider): Make sure that live_in always contains the
// CurrentContext variable to avoid the special case here.
if (FLAG_prune_dead_locals && !live_in->Contains(i) &&
(i != CurrentContextEnvIndex())) {
(*env)[i] = constant_dead();
}
}
}
// Attach environment to the block entry.
AttachEnvironment(block_entry, env);
#if defined(TARGET_ARCH_DBC)
// On DBC the exception/stacktrace variables are in special registers when
// entering the catch block. The only usage of those special registers is
// within the catch block. A possible lazy-deopt at the beginning of the
// catch does not need to move those around, since the registers will be
// up-to-date when arriving in the unoptimized code and unoptimized code will
// take care of moving them to appropriate slots.
if (CatchBlockEntryInstr* catch_entry = block_entry->AsCatchBlockEntry()) {
Environment* deopt_env = catch_entry->env();
const LocalVariable* raw_exception_var = catch_entry->raw_exception_var();
const LocalVariable* raw_stacktrace_var = catch_entry->raw_stacktrace_var();
if (raw_exception_var != nullptr) {
Value* value = deopt_env->ValueAt(EnvIndex(raw_exception_var));
value->BindToEnvironment(constant_null());
}
if (raw_stacktrace_var != nullptr) {
Value* value = deopt_env->ValueAt(EnvIndex(raw_stacktrace_var));
value->BindToEnvironment(constant_null());
}
}
#endif // defined(TARGET_ARCH_DBC)
// 2. Process normal instructions.
for (ForwardInstructionIterator it(block_entry); !it.Done(); it.Advance()) {
Instruction* current = it.Current();
// Attach current environment to the instructions that need it.
if (current->NeedsEnvironment()) {
AttachEnvironment(current, env);
}
// 2a. Handle uses:
// Update the expression stack renaming environment for each use by
// removing the renamed value.
// For each use of a LoadLocal, StoreLocal, MakeTemp, DropTemps or Constant:
// replace it with the renamed value.
for (intptr_t i = current->InputCount() - 1; i >= 0; --i) {
Value* v = current->InputAt(i);
// Update expression stack.
ASSERT(env->length() > variable_count());
Definition* reaching_defn = env->RemoveLast();
Definition* input_defn = v->definition();
if (input_defn != reaching_defn) {
// Note: constants can only be replaced with other constants.
ASSERT(input_defn->IsLoadLocal() || input_defn->IsStoreLocal() ||
input_defn->IsDropTemps() || input_defn->IsMakeTemp() ||
(input_defn->IsConstant() && reaching_defn->IsConstant()));
// Assert we are not referencing nulls in the initial environment.
ASSERT(reaching_defn->ssa_temp_index() != -1);
v->set_definition(reaching_defn);
input_defn = reaching_defn;
}
input_defn->AddInputUse(v);
}
// Drop pushed arguments for calls.
for (intptr_t j = 0; j < current->ArgumentCount(); j++) {
env->RemoveLast();
}
// 2b. Handle LoadLocal/StoreLocal/MakeTemp/DropTemps/Constant and
// PushArgument specially. Other definitions are just pushed
// to the environment directly.
Definition* result = NULL;
switch (current->tag()) {
case Instruction::kLoadLocal: {
LoadLocalInstr* load = current->Cast<LoadLocalInstr>();
// The graph construction ensures we do not have an unused LoadLocal
// computation.
ASSERT(load->HasTemp());
const intptr_t index = EnvIndex(&load->local());
result = (*env)[index];
PhiInstr* phi = result->AsPhi();
if ((phi != NULL) && !phi->is_alive()) {
phi->mark_alive();
live_phis->Add(phi);
}
if (FLAG_prune_dead_locals &&
variable_liveness->IsLastLoad(block_entry, load)) {
(*env)[index] = constant_dead();
}
// Record captured parameters so that they can be skipped when
// emitting sync code inside optimized try-blocks.
if (load->local().is_captured_parameter()) {
captured_parameters_->Add(index);
}
if ((phi != NULL) && isolate()->can_use_strong_mode_types()) {
// Assign type to Phi if it doesn't have a type yet.
// For a Phi to appear in the local variable it either was placed
// there as incoming value by renaming or it was stored there by
// StoreLocal which took this Phi from another local via LoadLocal,
// to which this reasoning applies recursively.
// This means that we are guaranteed to process LoadLocal for a
// matching variable first.
if (!phi->HasType()) {
ASSERT((index < phi->block()->phis()->length()) &&
((*phi->block()->phis())[index] == phi));
phi->UpdateType(
CompileType::FromAbstractType(load->local().type()));
}
}
break;
}
case Instruction::kStoreLocal: {
StoreLocalInstr* store = current->Cast<StoreLocalInstr>();
const intptr_t index = EnvIndex(&store->local());
result = store->value()->definition();
if (!FLAG_prune_dead_locals ||
variable_liveness->IsStoreAlive(block_entry, store)) {
(*env)[index] = result;
} else {
(*env)[index] = constant_dead();
}
break;
}
case Instruction::kDropTemps: {
// Drop temps from the environment.
DropTempsInstr* drop = current->Cast<DropTempsInstr>();
for (intptr_t j = 0; j < drop->num_temps(); j++) {
env->RemoveLast();
}
if (drop->value() != NULL) {
result = drop->value()->definition();
}
ASSERT((drop->value() != NULL) || !drop->HasTemp());
break;
}
case Instruction::kConstant: {
ConstantInstr* constant = current->Cast<ConstantInstr>();
if (constant->HasTemp()) {
result = GetConstant(constant->value());
}
break;
}
case Instruction::kMakeTemp: {
// Simply push a #null value to the expression stack.
result = constant_null_;
break;
}
case Instruction::kPushArgument:
env->Add(current->Cast<PushArgumentInstr>());
continue;
default:
// Other definitions directly go into the environment.
if (Definition* definition = current->AsDefinition()) {
if (definition->HasTemp()) {
// Assign fresh SSA temporary and update expression stack.
AllocateSSAIndexes(definition);
env->Add(definition);
}
}
continue;
}
// Update expression stack and remove current instruction from the graph.
Definition* definition = current->Cast<Definition>();
if (definition->HasTemp()) {
ASSERT(result != NULL);
env->Add(result);
}
it.RemoveCurrentFromGraph();
}
// 3. Process dominated blocks.
for (intptr_t i = 0; i < block_entry->dominated_blocks().length(); ++i) {
BlockEntryInstr* block = block_entry->dominated_blocks()[i];
GrowableArray<Definition*> new_env(env->length());
new_env.AddArray(*env);
RenameRecursive(block, &new_env, live_phis, variable_liveness,
inlining_parameters);
}
// 4. Process successor block. We have edge-split form, so that only blocks
// with one successor can have a join block as successor.
if ((block_entry->last_instruction()->SuccessorCount() == 1) &&
block_entry->last_instruction()->SuccessorAt(0)->IsJoinEntry()) {
JoinEntryInstr* successor =
block_entry->last_instruction()->SuccessorAt(0)->AsJoinEntry();
intptr_t pred_index = successor->IndexOfPredecessor(block_entry);
ASSERT(pred_index >= 0);
if (successor->phis() != NULL) {
for (intptr_t i = 0; i < successor->phis()->length(); ++i) {
PhiInstr* phi = (*successor->phis())[i];
if (phi != NULL) {
// Rename input operand.
Value* use = new (zone()) Value((*env)[i]);
phi->SetInputAt(pred_index, use);
}
}
}
}
}
void FlowGraph::RemoveDeadPhis(GrowableArray<PhiInstr*>* live_phis) {
// Augment live_phis with those that have implicit real used at
// potentially throwing instructions if there is a try-catch in this graph.
if (!graph_entry()->catch_entries().is_empty()) {
for (BlockIterator it(postorder_iterator()); !it.Done(); it.Advance()) {
JoinEntryInstr* join = it.Current()->AsJoinEntry();
if (join == NULL) continue;
for (PhiIterator phi_it(join); !phi_it.Done(); phi_it.Advance()) {
PhiInstr* phi = phi_it.Current();
if (phi == NULL || phi->is_alive() || (phi->input_use_list() != NULL) ||
(phi->env_use_list() == NULL)) {
continue;
}
for (Value::Iterator it(phi->env_use_list()); !it.Done();
it.Advance()) {
Value* use = it.Current();
if (use->instruction()->MayThrow() &&
use->instruction()->GetBlock()->InsideTryBlock()) {
live_phis->Add(phi);
phi->mark_alive();
break;
}
}
}
}
}
while (!live_phis->is_empty()) {
PhiInstr* phi = live_phis->RemoveLast();
for (intptr_t i = 0; i < phi->InputCount(); i++) {
Value* val = phi->InputAt(i);
PhiInstr* used_phi = val->definition()->AsPhi();
if ((used_phi != NULL) && !used_phi->is_alive()) {
used_phi->mark_alive();
live_phis->Add(used_phi);
}
}
}
for (BlockIterator it(postorder_iterator()); !it.Done(); it.Advance()) {
JoinEntryInstr* join = it.Current()->AsJoinEntry();
if (join != NULL) join->RemoveDeadPhis(constant_dead());
}
}
RedefinitionInstr* FlowGraph::EnsureRedefinition(Instruction* prev,
Definition* original,
CompileType compile_type) {
RedefinitionInstr* first = prev->next()->AsRedefinition();
if (first != NULL && (first->constrained_type() != NULL)) {
if ((first->value()->definition() == original) &&
first->constrained_type()->IsEqualTo(&compile_type)) {
// Already redefined. Do nothing.
return NULL;
}
}
RedefinitionInstr* redef = new RedefinitionInstr(new Value(original));
// Don't set the constrained type when the type is None(), which denotes an
// unreachable value (e.g. using value null after some form of null check).
if (!compile_type.IsNone()) {
redef->set_constrained_type(new CompileType(compile_type));
}
InsertAfter(prev, redef, NULL, FlowGraph::kValue);
RenameDominatedUses(original, redef, redef);
return redef;
}
void FlowGraph::RemoveRedefinitions(bool keep_checks) {
// Remove redefinition and check instructions that were inserted
// to make a control dependence explicit with a data dependence,
// for example, to inhibit hoisting.
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
thread()->CheckForSafepoint();
for (ForwardInstructionIterator instr_it(block_it.Current());
!instr_it.Done(); instr_it.Advance()) {
Instruction* instruction = instr_it.Current();
if (auto redef = instruction->AsRedefinition()) {
redef->ReplaceUsesWith(redef->value()->definition());
instr_it.RemoveCurrentFromGraph();
} else if (keep_checks) {
continue;
} else if (auto check = instruction->AsCheckArrayBound()) {
check->ReplaceUsesWith(check->index()->definition());
check->ClearSSATempIndex();
} else if (auto check = instruction->AsGenericCheckBound()) {
check->ReplaceUsesWith(check->index()->definition());
check->ClearSSATempIndex();
} else if (auto check = instruction->AsCheckNull()) {
check->ReplaceUsesWith(check->value()->definition());
check->ClearSSATempIndex();
}
}
}
}
BitVector* FlowGraph::FindLoopBlocks(BlockEntryInstr* m,
BlockEntryInstr* n) const {
GrowableArray<BlockEntryInstr*> stack;
BitVector* loop_blocks = new (zone()) BitVector(zone(), preorder_.length());
loop_blocks->Add(n->preorder_number());
if (n != m) {
loop_blocks->Add(m->preorder_number());
stack.Add(m);
}
while (!stack.is_empty()) {
BlockEntryInstr* p = stack.RemoveLast();
for (intptr_t i = 0; i < p->PredecessorCount(); ++i) {
BlockEntryInstr* q = p->PredecessorAt(i);
if (!loop_blocks->Contains(q->preorder_number())) {
loop_blocks->Add(q->preorder_number());
stack.Add(q);
}
}
}
return loop_blocks;
}
LoopHierarchy* FlowGraph::ComputeLoops() const {
// Iterate over all entry blocks in the flow graph to attach
// loop information to each loop header.
ZoneGrowableArray<BlockEntryInstr*>* loop_headers =
new (zone()) ZoneGrowableArray<BlockEntryInstr*>();
for (BlockIterator it = postorder_iterator(); !it.Done(); it.Advance()) {
BlockEntryInstr* block = it.Current();
// Reset loop information on every entry block (since this method
// may recompute loop information on a modified flow graph).
block->set_loop_info(nullptr);
// Iterate over predecessors to find back edges.
for (intptr_t i = 0; i < block->PredecessorCount(); ++i) {
BlockEntryInstr* pred = block->PredecessorAt(i);
if (block->Dominates(pred)) {
// Identify the block as a loop header and add the blocks in the
// loop to the loop information. Loops that share the same loop
// header are treated as one loop by merging these blocks.
BitVector* loop_blocks = FindLoopBlocks(pred, block);
if (block->loop_info() == nullptr) {
intptr_t id = loop_headers->length();
block->set_loop_info(new (zone()) LoopInfo(id, block, loop_blocks));
loop_headers->Add(block);
} else {
ASSERT(block->loop_info()->header() == block);
block->loop_info()->AddBlocks(loop_blocks);
}
block->loop_info()->AddBackEdge(pred);
}
}
}
// Build the loop hierarchy and link every entry block to
// the closest enveloping loop in loop hierarchy.
return new (zone()) LoopHierarchy(loop_headers, preorder_);
}
intptr_t FlowGraph::InstructionCount() const {
intptr_t size = 0;
// Iterate each block, skipping the graph entry.
for (intptr_t i = 1; i < preorder_.length(); ++i) {
BlockEntryInstr* block = preorder_[i];
// Skip any blocks from the prologue to make them not count towards the
// inlining instruction budget.
const intptr_t block_id = block->block_id();
if (prologue_info_.Contains(block_id)) {
continue;
}
for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
++size;
}
}
return size;
}
void FlowGraph::ConvertUse(Value* use, Representation from_rep) {
const Representation to_rep =
use->instruction()->RequiredInputRepresentation(use->use_index());
if (from_rep == to_rep || to_rep == kNoRepresentation) {
return;
}
InsertConversion(from_rep, to_rep, use, /*is_environment_use=*/false);
}
static bool IsUnboxedInteger(Representation rep) {
return (rep == kUnboxedInt32) || (rep == kUnboxedUint32) ||
(rep == kUnboxedInt64);
}
static bool ShouldInlineSimd() {
return FlowGraphCompiler::SupportsUnboxedSimd128();
}
static bool CanUnboxDouble() {
return FlowGraphCompiler::SupportsUnboxedDoubles();
}
static bool CanConvertInt64ToDouble() {
return FlowGraphCompiler::CanConvertInt64ToDouble();
}
void FlowGraph::InsertConversion(Representation from,
Representation to,
Value* use,
bool is_environment_use) {
Instruction* insert_before;
Instruction* deopt_target;
PhiInstr* phi = use->instruction()->AsPhi();
if (phi != NULL) {
ASSERT(phi->is_alive());
// For phis conversions have to be inserted in the predecessor.
auto predecessor = phi->block()->PredecessorAt(use->use_index());
insert_before = predecessor->last_instruction();
ASSERT(insert_before->GetBlock() == predecessor);
deopt_target = NULL;
} else {
deopt_target = insert_before = use->instruction();
}
Definition* converted = NULL;
if (IsUnboxedInteger(from) && IsUnboxedInteger(to)) {
const intptr_t deopt_id = (to == kUnboxedInt32) && (deopt_target != NULL)
? deopt_target->DeoptimizationTarget()
: DeoptId::kNone;
converted = new (Z)
UnboxedIntConverterInstr(from, to, use->CopyWithType(), deopt_id);
} else if ((from == kUnboxedInt32) && (to == kUnboxedDouble)) {
converted = new Int32ToDoubleInstr(use->CopyWithType());
} else if ((from == kUnboxedInt64) && (to == kUnboxedDouble) &&
CanConvertInt64ToDouble()) {
const intptr_t deopt_id = (deopt_target != NULL)
? deopt_target->DeoptimizationTarget()
: DeoptId::kNone;
ASSERT(CanUnboxDouble());
converted = new Int64ToDoubleInstr(use->CopyWithType(), deopt_id);
} else if ((from == kTagged) && Boxing::Supports(to)) {
const intptr_t deopt_id = (deopt_target != NULL)
? deopt_target->DeoptimizationTarget()
: DeoptId::kNone;
converted = UnboxInstr::Create(to, use->CopyWithType(), deopt_id,
use->instruction()->speculative_mode());
} else if ((to == kTagged) && Boxing::Supports(from)) {
converted = BoxInstr::Create(from, use->CopyWithType());
} else {
// We have failed to find a suitable conversion instruction.
// Insert two "dummy" conversion instructions with the correct
// "from" and "to" representation. The inserted instructions will
// trigger a deoptimization if executed. See #12417 for a discussion.
const intptr_t deopt_id = (deopt_target != NULL)
? deopt_target->DeoptimizationTarget()
: DeoptId::kNone;
ASSERT(Boxing::Supports(from));
ASSERT(Boxing::Supports(to));
Definition* boxed = BoxInstr::Create(from, use->CopyWithType());
use->BindTo(boxed);
InsertBefore(insert_before, boxed, NULL, FlowGraph::kValue);
converted = UnboxInstr::Create(to, new (Z) Value(boxed), deopt_id);
}
ASSERT(converted != NULL);
InsertBefore(insert_before, converted, use->instruction()->env(),
FlowGraph::kValue);
if (is_environment_use) {
use->BindToEnvironment(converted);
} else {
use->BindTo(converted);
}
if ((to == kUnboxedInt32) && (phi != NULL)) {
// Int32 phis are unboxed optimistically. Ensure that unboxing
// has deoptimization target attached from the goto instruction.
CopyDeoptTarget(converted, insert_before);
}
}
void FlowGraph::InsertConversionsFor(Definition* def) {
const Representation from_rep = def->representation();
for (Value::Iterator it(def->input_use_list()); !it.Done(); it.Advance()) {
ConvertUse(it.Current(), from_rep);
}
}
static void UnboxPhi(PhiInstr* phi) {
Representation unboxed = phi->representation();
switch (phi->Type()->ToCid()) {
case kDoubleCid:
if (CanUnboxDouble()) {
unboxed = kUnboxedDouble;
}
break;
case kFloat32x4Cid:
if (ShouldInlineSimd()) {
unboxed = kUnboxedFloat32x4;
}
break;
case kInt32x4Cid:
if (ShouldInlineSimd()) {
unboxed = kUnboxedInt32x4;
}
break;
case kFloat64x2Cid:
if (ShouldInlineSimd()) {
unboxed = kUnboxedFloat64x2;
}
break;
}
// If all the inputs are unboxed, leave the Phi unboxed.
if ((unboxed == kTagged) && phi->Type()->IsInt()) {
bool should_unbox = true;
Representation new_representation = kTagged;
for (intptr_t i = 0; i < phi->InputCount(); i++) {
Definition* input = phi->InputAt(i)->definition();
if (input->representation() != kUnboxedInt64 &&
input->representation() != kUnboxedInt32 &&
input->representation() != kUnboxedUint32 && !(input == phi)) {
should_unbox = false;
break;
}
if (new_representation == kTagged) {
new_representation = input->representation();
} else if (new_representation != input->representation()) {
new_representation = kNoRepresentation;
}
}
if (should_unbox) {
unboxed = new_representation != kNoRepresentation
? new_representation
: RangeUtils::Fits(phi->range(),
RangeBoundary::kRangeBoundaryInt32)
? kUnboxedInt32
: kUnboxedInt64;
}
}
if ((unboxed == kTagged) && phi->Type()->IsInt()) {
// Conservatively unbox phis that:
// - are proven to be of type Int;
// - fit into 64bits range;
// - have either constants or Box() operations as inputs;
// - have at least one Box() operation as an input;
// - are used in at least 1 Unbox() operation.
bool should_unbox = false;
for (intptr_t i = 0; i < phi->InputCount(); i++) {
Definition* input = phi->InputAt(i)->definition();
if (input->IsBox()) {
should_unbox = true;
} else if (!input->IsConstant()) {
should_unbox = false;
break;
}
}
if (should_unbox) {
// We checked inputs. Check if phi is used in at least one unbox
// operation.
bool has_unboxed_use = false;
for (Value* use = phi->input_use_list(); use != NULL;
use = use->next_use()) {
Instruction* instr = use->instruction();
if (instr->IsUnbox()) {
has_unboxed_use = true;
break;
} else if (IsUnboxedInteger(
instr->RequiredInputRepresentation(use->use_index()))) {
has_unboxed_use = true;
break;
}
}
if (!has_unboxed_use) {
should_unbox = false;
}
}
if (should_unbox) {
unboxed =
RangeUtils::Fits(phi->range(), RangeBoundary::kRangeBoundaryInt32)
? kUnboxedInt32
: kUnboxedInt64;
}
}
phi->set_representation(unboxed);
}
void FlowGraph::SelectRepresentations() {
// First we decide for each phi if it is beneficial to unbox it. If so, we
// change it's `phi->representation()`
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
JoinEntryInstr* join_entry = block_it.Current()->AsJoinEntry();
if (join_entry != NULL) {
for (PhiIterator it(join_entry); !it.Done(); it.Advance()) {
PhiInstr* phi = it.Current();
UnboxPhi(phi);
}
}
}
// Process all initial definitions and insert conversions when needed (depends
// on phi unboxing decision above).
for (intptr_t i = 0; i < graph_entry()->initial_definitions()->length();
i++) {
InsertConversionsFor((*graph_entry()->initial_definitions())[i]);
}
for (intptr_t i = 0; i < graph_entry()->SuccessorCount(); ++i) {
auto successor = graph_entry()->SuccessorAt(i);
if (auto entry = successor->AsBlockEntryWithInitialDefs()) {
auto& initial_definitions = *entry->initial_definitions();
for (intptr_t j = 0; j < initial_definitions.length(); j++) {
InsertConversionsFor(initial_definitions[j]);
}
}
}
// Process all normal definitions and insert conversions when needed (depends
// on phi unboxing decision above).
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
BlockEntryInstr* entry = block_it.Current();
if (JoinEntryInstr* join_entry = entry->AsJoinEntry()) {
for (PhiIterator it(join_entry); !it.Done(); it.Advance()) {
PhiInstr* phi = it.Current();
ASSERT(phi != NULL);
ASSERT(phi->is_alive());
InsertConversionsFor(phi);
}
}
for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
Definition* def = it.Current()->AsDefinition();
if (def != NULL) {
InsertConversionsFor(def);
}
}
}
}
#if defined(TARGET_ARCH_ARM) || defined(TARGET_ARCH_IA32)
// Smi widening pass is only meaningful on platforms where Smi
// is smaller than 32bit. For now only support it on ARM and ia32.
static bool CanBeWidened(BinarySmiOpInstr* smi_op) {
return BinaryInt32OpInstr::IsSupported(smi_op->op_kind(), smi_op->left(),
smi_op->right());
}
static bool BenefitsFromWidening(BinarySmiOpInstr* smi_op) {
// TODO(vegorov): when shifts with non-constants shift count are supported
// add them here as we save untagging for the count.
switch (smi_op->op_kind()) {
case Token::kMUL:
case Token::kSHR:
// For kMUL we save untagging of the argument for kSHR
// we save tagging of the result.
return true;
default:
return false;
}
}
// Maps an entry block to its closest enveloping loop id, or -1 if none.
static intptr_t LoopId(BlockEntryInstr* block) {
LoopInfo* loop = block->loop_info();
if (loop != nullptr) {
return loop->id();
}
return -1;
}
void FlowGraph::WidenSmiToInt32() {
if (!FLAG_use_smi_widening) {
return;
}
GrowableArray<BinarySmiOpInstr*> candidates;
// Step 1. Collect all instructions that potentially benefit from widening of
// their operands (or their result) into int32 range.
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
for (ForwardInstructionIterator instr_it(block_it.Current());
!instr_it.Done(); instr_it.Advance()) {
BinarySmiOpInstr* smi_op = instr_it.Current()->AsBinarySmiOp();
if ((smi_op != NULL) && smi_op->HasSSATemp() &&
BenefitsFromWidening(smi_op) && CanBeWidened(smi_op)) {
candidates.Add(smi_op);
}
}
}
if (candidates.is_empty()) {
return;
}
// Step 2. For each block in the graph compute which loop it belongs to.
// We will use this information later during computation of the widening's
// gain: we are going to assume that only conversion occurring inside the
// same loop should be counted against the gain, all other conversions
// can be hoisted and thus cost nothing compared to the loop cost itself.
GetLoopHierarchy();
// Step 3. For each candidate transitively collect all other BinarySmiOpInstr
// and PhiInstr that depend on it and that it depends on and count amount of
// untagging operations that we save in assumption that this whole graph of
// values is using kUnboxedInt32 representation instead of kTagged.
// Convert those graphs that have positive gain to kUnboxedInt32.
// BitVector containing SSA indexes of all processed definitions. Used to skip
// those candidates that belong to dependency graph of another candidate.
BitVector* processed = new (Z) BitVector(Z, current_ssa_temp_index());
// Worklist used to collect dependency graph.
DefinitionWorklist worklist(this, candidates.length());
for (intptr_t i = 0; i < candidates.length(); i++) {
BinarySmiOpInstr* op = candidates[i];
if (op->WasEliminated() || processed->Contains(op->ssa_temp_index())) {
continue;
}
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("analysing candidate: %s\n", op->ToCString());
}
worklist.Clear();
worklist.Add(op);
// Collect dependency graph. Note: more items are added to worklist
// inside this loop.
intptr_t gain = 0;
for (intptr_t j = 0; j < worklist.definitions().length(); j++) {
Definition* defn = worklist.definitions()[j];
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("> %s\n", defn->ToCString());
}
if (defn->IsBinarySmiOp() &&
BenefitsFromWidening(defn->AsBinarySmiOp())) {
gain++;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("^ [%" Pd "] (o) %s\n", gain, defn->ToCString());
}
}
const intptr_t defn_loop = LoopId(defn->GetBlock());
// Process all inputs.
for (intptr_t k = 0; k < defn->InputCount(); k++) {
Definition* input = defn->InputAt(k)->definition();
if (input->IsBinarySmiOp() && CanBeWidened(input->AsBinarySmiOp())) {
worklist.Add(input);
} else if (input->IsPhi() && (input->Type()->ToCid() == kSmiCid)) {
worklist.Add(input);
} else if (input->IsBinaryInt64Op()) {
// Mint operation produces untagged result. We avoid tagging.
gain++;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("^ [%" Pd "] (i) %s\n", gain, input->ToCString());
}
} else if (defn_loop == LoopId(input->GetBlock()) &&
(input->Type()->ToCid() == kSmiCid)) {
// Input comes from the same loop, is known to be smi and requires
// untagging.
// TODO(vegorov) this heuristic assumes that values that are not
// known to be smi have to be checked and this check can be
// coalesced with untagging. Start coalescing them.
gain--;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("v [%" Pd "] (i) %s\n", gain, input->ToCString());
}
}
}
// Process all uses.
for (Value* use = defn->input_use_list(); use != NULL;
use = use->next_use()) {
Instruction* instr = use->instruction();
Definition* use_defn = instr->AsDefinition();
if (use_defn == NULL) {
// We assume that tagging before returning or pushing argument costs
// very little compared to the cost of the return/call itself.
if (!instr->IsReturn() && !instr->IsPushArgument()) {
gain--;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("v [%" Pd "] (u) %s\n", gain,
use->instruction()->ToCString());
}
}
continue;
} else if (use_defn->IsBinarySmiOp() &&
CanBeWidened(use_defn->AsBinarySmiOp())) {
worklist.Add(use_defn);
} else if (use_defn->IsPhi() &&
use_defn->AsPhi()->Type()->ToCid() == kSmiCid) {
worklist.Add(use_defn);
} else if (use_defn->IsBinaryInt64Op()) {
// BinaryInt64Op requires untagging of its inputs.
// Converting kUnboxedInt32 to kUnboxedInt64 is essentially zero cost
// sign extension operation.
gain++;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("^ [%" Pd "] (u) %s\n", gain,
use->instruction()->ToCString());
}
} else if (defn_loop == LoopId(instr->GetBlock())) {
gain--;
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("v [%" Pd "] (u) %s\n", gain,
use->instruction()->ToCString());
}
}
}
}
processed->AddAll(worklist.contains_vector());
if (FLAG_support_il_printer && FLAG_trace_smi_widening) {
THR_Print("~ %s gain %" Pd "\n", op->ToCString(), gain);
}
if (gain > 0) {
// We have positive gain from widening. Convert all BinarySmiOpInstr into
// BinaryInt32OpInstr and set representation of all phis to kUnboxedInt32.
for (intptr_t j = 0; j < worklist.definitions().length(); j++) {
Definition* defn = worklist.definitions()[j];
ASSERT(defn->IsPhi() || defn->IsBinarySmiOp());
// Since we widen the integer representation we've to clear out type
// propagation information (e.g. it might no longer be a _Smi).
for (Value::Iterator it(defn->input_use_list()); !it.Done();
it.Advance()) {
it.Current()->SetReachingType(NULL);
}
if (defn->IsBinarySmiOp()) {
BinarySmiOpInstr* smi_op = defn->AsBinarySmiOp();
BinaryInt32OpInstr* int32_op = new (Z) BinaryInt32OpInstr(
smi_op->op_kind(), smi_op->left()->CopyWithType(),
smi_op->right()->CopyWithType(), smi_op->DeoptimizationTarget());
smi_op->ReplaceWith(int32_op, NULL);
} else if (defn->IsPhi()) {
defn->AsPhi()->set_representation(kUnboxedInt32);
ASSERT(defn->Type()->IsInt());
}
}
}
}
}
#else
void FlowGraph::WidenSmiToInt32() {
// TODO(vegorov) ideally on 64-bit platforms we would like to narrow smi
// operations to 32-bit where it saves tagging and untagging and allows
// to use shorted (and faster) instructions. But we currently don't
// save enough range information in the ICData to drive this decision.
}
#endif
void FlowGraph::EliminateEnvironments() {
// After this pass we can no longer perform LICM and hoist instructions
// that can deoptimize.
disallow_licm();
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
BlockEntryInstr* block = block_it.Current();
if (!block->IsCatchBlockEntry()) {
block->RemoveEnvironment();
}
for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
Instruction* current = it.Current();
if (!current->ComputeCanDeoptimize() &&
(!current->MayThrow() || !current->GetBlock()->InsideTryBlock())) {
// Instructions that can throw need an environment for optimized
// try-catch.
// TODO(srdjan): --source-lines needs deopt environments to get at
// the code for this instruction, however, leaving the environment
// changes code.
current->RemoveEnvironment();
}
}
}
}
bool FlowGraph::Canonicalize() {
bool changed = false;
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
for (ForwardInstructionIterator it(block_it.Current()); !it.Done();
it.Advance()) {
Instruction* current = it.Current();
if (current->HasUnmatchedInputRepresentations()) {
// Can't canonicalize this instruction until all conversions for its
// inputs are inserted.
continue;
}
Instruction* replacement = current->Canonicalize(this);
if (replacement != current) {
// For non-definitions Canonicalize should return either NULL or
// this.
ASSERT((replacement == NULL) || current->IsDefinition());
ReplaceCurrentInstruction(&it, current, replacement);
changed = true;
}
}
}
return changed;
}
void FlowGraph::PopulateWithICData(const Function& function) {
Zone* zone = Thread::Current()->zone();
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
ForwardInstructionIterator it(block_it.Current());
for (; !it.Done(); it.Advance()) {
Instruction* instr = it.Current();
if (instr->IsInstanceCall()) {
InstanceCallInstr* call = instr->AsInstanceCall();
if (!call->HasICData()) {
const Array& arguments_descriptor =
Array::Handle(zone, call->GetArgumentsDescriptor());
const ICData& ic_data = ICData::ZoneHandle(
zone,
ICData::New(function, call->function_name(), arguments_descriptor,
call->deopt_id(), call->checked_argument_count(),
ICData::kInstance));
call->set_ic_data(&ic_data);
}
} else if (instr->IsStaticCall()) {
StaticCallInstr* call = instr->AsStaticCall();
if (!call->HasICData()) {
const Array& arguments_descriptor =
Array::Handle(zone, call->GetArgumentsDescriptor());
const Function& target = call->function();
int num_args_checked =
MethodRecognizer::NumArgsCheckedForStaticCall(target);
const ICData& ic_data = ICData::ZoneHandle(
zone, ICData::New(function, String::Handle(zone, target.name()),
arguments_descriptor, call->deopt_id(),
num_args_checked, ICData::kStatic));
ic_data.AddTarget(target);
call->set_ic_data(&ic_data);
}
}
}
}
}
// Optimize (a << b) & c pattern: if c is a positive Smi or zero, then the
// shift can be a truncating Smi shift-left and result is always Smi.
// Merging occurs only per basic-block.
void FlowGraph::TryOptimizePatterns() {
if (!FLAG_truncating_left_shift) return;
GrowableArray<BinarySmiOpInstr*> div_mod_merge;
GrowableArray<InvokeMathCFunctionInstr*> sin_cos_merge;
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
// Merging only per basic-block.
div_mod_merge.Clear();
sin_cos_merge.Clear();
ForwardInstructionIterator it(block_it.Current());
for (; !it.Done(); it.Advance()) {
if (it.Current()->IsBinarySmiOp()) {
BinarySmiOpInstr* binop = it.Current()->AsBinarySmiOp();
if (binop->op_kind() == Token::kBIT_AND) {
OptimizeLeftShiftBitAndSmiOp(&it, binop, binop->left()->definition(),
binop->right()->definition());
} else if ((binop->op_kind() == Token::kTRUNCDIV) ||
(binop->op_kind() == Token::kMOD)) {
if (binop->HasUses()) {
div_mod_merge.Add(binop);
}
}
} else if (it.Current()->IsBinaryInt64Op()) {
BinaryInt64OpInstr* mintop = it.Current()->AsBinaryInt64Op();
if (mintop->op_kind() == Token::kBIT_AND) {
OptimizeLeftShiftBitAndSmiOp(&it, mintop,
mintop->left()->definition(),
mintop->right()->definition());
}
} else if (it.Current()->IsInvokeMathCFunction()) {
InvokeMathCFunctionInstr* math_unary =
it.Current()->AsInvokeMathCFunction();
if ((math_unary->recognized_kind() == MethodRecognizer::kMathSin) ||
(math_unary->recognized_kind() == MethodRecognizer::kMathCos)) {
if (math_unary->HasUses()) {
sin_cos_merge.Add(math_unary);
}
}
}
}
TryMergeTruncDivMod(&div_mod_merge);
}
}
// Returns true if use is dominated by the given instruction.
// Note: uses that occur at instruction itself are not dominated by it.
static bool IsDominatedUse(Instruction* dom, Value* use) {
BlockEntryInstr* dom_block = dom->GetBlock();
Instruction* instr = use->instruction();
PhiInstr* phi = instr->AsPhi();
if (phi != NULL) {
return dom_block->Dominates(phi->block()->PredecessorAt(use->use_index()));
}
BlockEntryInstr* use_block = instr->GetBlock();
if (use_block == dom_block) {
// Fast path for the case of block entry.
if (dom_block == dom) return true;
for (Instruction* curr = dom->next(); curr != NULL; curr = curr->next()) {
if (curr == instr) return true;
}
return false;
}
return dom_block->Dominates(use_block);
}
void FlowGraph::RenameDominatedUses(Definition* def,
Instruction* dom,
Definition* other) {
for (Value::Iterator it(def->input_use_list()); !it.Done(); it.Advance()) {
Value* use = it.Current();
if (IsDominatedUse(dom, use)) {
use->BindTo(other);
}
}
}
void FlowGraph::RenameUsesDominatedByRedefinitions() {
for (BlockIterator block_it = reverse_postorder_iterator(); !block_it.Done();
block_it.Advance()) {
for (ForwardInstructionIterator instr_it(block_it.Current());
!instr_it.Done(); instr_it.Advance()) {
RedefinitionInstr* redefinition = instr_it.Current()->AsRedefinition();
if (redefinition != NULL) {
Definition* original = redefinition->value()->definition();
RenameDominatedUses(original, redefinition, redefinition);
}
}
}
}
static bool IsPositiveOrZeroSmiConst(Definition* d) {
ConstantInstr* const_instr = d->AsConstant();
if ((const_instr != NULL) && (const_instr->value().IsSmi())) {
return Smi::Cast(const_instr->value()).Value() >= 0;
}
return false;
}
static BinarySmiOpInstr* AsSmiShiftLeftInstruction(Definition* d) {
BinarySmiOpInstr* instr = d->AsBinarySmiOp();
if ((instr != NULL) && (instr->op_kind() == Token::kSHL)) {
return instr;
}
return NULL;
}
void FlowGraph::OptimizeLeftShiftBitAndSmiOp(
ForwardInstructionIterator* current_iterator,
Definition* bit_and_instr,
Definition* left_instr,
Definition* right_instr) {
ASSERT(bit_and_instr != NULL);
ASSERT((left_instr != NULL) && (right_instr != NULL));
// Check for pattern, smi_shift_left must be single-use.
bool is_positive_or_zero = IsPositiveOrZeroSmiConst(left_instr);
if (!is_positive_or_zero) {
is_positive_or_zero = IsPositiveOrZeroSmiConst(right_instr);
}
if (!is_positive_or_zero) return;
BinarySmiOpInstr* smi_shift_left = NULL;
if (bit_and_instr->InputAt(0)->IsSingleUse()) {
smi_shift_left = AsSmiShiftLeftInstruction(left_instr);
}
if ((smi_shift_left == NULL) && (bit_and_instr->InputAt(1)->IsSingleUse())) {
smi_shift_left = AsSmiShiftLeftInstruction(right_instr);
}
if (smi_shift_left == NULL) return;
// Pattern recognized.
smi_shift_left->mark_truncating();
ASSERT(bit_and_instr->IsBinarySmiOp() || bit_and_instr->IsBinaryInt64Op());
if (bit_and_instr->IsBinaryInt64Op()) {
// Replace Mint op with Smi op.
BinarySmiOpInstr* smi_op = new (Z) BinarySmiOpInstr(
Token::kBIT_AND, new (Z) Value(left_instr), new (Z) Value(right_instr),
DeoptId::kNone); // BIT_AND cannot deoptimize.
bit_and_instr->ReplaceWith(smi_op, current_iterator);
}
}
// Dart:
// var x = d % 10;
// var y = d ~/ 10;
// var z = x + y;
//
// IL:
// v4 <- %(v2, v3)
// v5 <- ~/(v2, v3)
// v6 <- +(v4, v5)
//
// IL optimized:
// v4 <- DIVMOD(v2, v3);
// v5 <- LoadIndexed(v4, 0); // ~/ result
// v6 <- LoadIndexed(v4, 1); // % result
// v7 <- +(v5, v6)
// Because of the environment it is important that merged instruction replaces
// first original instruction encountered.
void FlowGraph::TryMergeTruncDivMod(
GrowableArray<BinarySmiOpInstr*>* merge_candidates) {
if (merge_candidates->length() < 2) {
// Need at least a TRUNCDIV and a MOD.
return;
}
for (intptr_t i = 0; i < merge_candidates->length(); i++) {
BinarySmiOpInstr* curr_instr = (*merge_candidates)[i];
if (curr_instr == NULL) {
// Instruction was merged already.
continue;
}
ASSERT((curr_instr->op_kind() == Token::kTRUNCDIV) ||
(curr_instr->op_kind() == Token::kMOD));
// Check if there is kMOD/kTRUNDIV binop with same inputs.
const Token::Kind other_kind = (curr_instr->op_kind() == Token::kTRUNCDIV)
? Token::kMOD
: Token::kTRUNCDIV;
Definition* left_def = curr_instr->left()->definition();
Definition* right_def = curr_instr->right()->definition();
for (intptr_t k = i + 1; k < merge_candidates->length(); k++) {
BinarySmiOpInstr* other_binop = (*merge_candidates)[k];
// 'other_binop' can be NULL if it was already merged.
if ((other_binop != NULL) && (other_binop->op_kind() == other_kind) &&
(other_binop->left()->definition() == left_def) &&
(other_binop->right()->definition() == right_def)) {
(*