| // Copyright 2013 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/crankshaft/hydrogen-infer-representation.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| void HInferRepresentationPhase::AddToWorklist(HValue* current) { |
| if (current->representation().IsTagged()) return; |
| if (!current->CheckFlag(HValue::kFlexibleRepresentation)) return; |
| if (in_worklist_.Contains(current->id())) return; |
| worklist_.Add(current, zone()); |
| in_worklist_.Add(current->id()); |
| } |
| |
| |
| void HInferRepresentationPhase::Run() { |
| // (1) Initialize bit vectors and count real uses. Each phi gets a |
| // bit-vector of length <number of phis>. |
| const ZoneList<HPhi*>* phi_list = graph()->phi_list(); |
| int phi_count = phi_list->length(); |
| ZoneList<BitVector*> connected_phis(phi_count, zone()); |
| for (int i = 0; i < phi_count; ++i) { |
| phi_list->at(i)->InitRealUses(i); |
| BitVector* connected_set = new(zone()) BitVector(phi_count, zone()); |
| connected_set->Add(i); |
| connected_phis.Add(connected_set, zone()); |
| } |
| |
| // (2) Do a fixed point iteration to find the set of connected phis. A |
| // phi is connected to another phi if its value is used either directly or |
| // indirectly through a transitive closure of the def-use relation. |
| bool change = true; |
| while (change) { |
| change = false; |
| // We normally have far more "forward edges" than "backward edges", |
| // so we terminate faster when we walk backwards. |
| for (int i = phi_count - 1; i >= 0; --i) { |
| HPhi* phi = phi_list->at(i); |
| for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) { |
| HValue* use = it.value(); |
| if (use->IsPhi()) { |
| int id = HPhi::cast(use)->phi_id(); |
| if (connected_phis[i]->UnionIsChanged(*connected_phis[id])) |
| change = true; |
| } |
| } |
| } |
| } |
| |
| // Set truncation flags for groups of connected phis. This is a conservative |
| // approximation; the flag will be properly re-computed after representations |
| // have been determined. |
| if (phi_count > 0) { |
| BitVector done(phi_count, zone()); |
| for (int i = 0; i < phi_count; ++i) { |
| if (done.Contains(i)) continue; |
| |
| // Check if all uses of all connected phis in this group are truncating. |
| bool all_uses_everywhere_truncating_int32 = true; |
| bool all_uses_everywhere_truncating_smi = true; |
| for (BitVector::Iterator it(connected_phis[i]); |
| !it.Done(); |
| it.Advance()) { |
| int index = it.Current(); |
| all_uses_everywhere_truncating_int32 &= |
| phi_list->at(index)->CheckFlag(HInstruction::kTruncatingToInt32); |
| all_uses_everywhere_truncating_smi &= |
| phi_list->at(index)->CheckFlag(HInstruction::kTruncatingToSmi); |
| done.Add(index); |
| } |
| |
| if (!all_uses_everywhere_truncating_int32) { |
| // Clear truncation flag of this group of connected phis. |
| for (BitVector::Iterator it(connected_phis[i]); |
| !it.Done(); |
| it.Advance()) { |
| int index = it.Current(); |
| phi_list->at(index)->ClearFlag(HInstruction::kTruncatingToInt32); |
| } |
| } |
| if (!all_uses_everywhere_truncating_smi) { |
| // Clear truncation flag of this group of connected phis. |
| for (BitVector::Iterator it(connected_phis[i]); |
| !it.Done(); |
| it.Advance()) { |
| int index = it.Current(); |
| phi_list->at(index)->ClearFlag(HInstruction::kTruncatingToSmi); |
| } |
| } |
| } |
| } |
| |
| // Simplify constant phi inputs where possible. |
| // This step uses kTruncatingToInt32 flags of phis. |
| for (int i = 0; i < phi_count; ++i) { |
| phi_list->at(i)->SimplifyConstantInputs(); |
| } |
| |
| // Use the phi reachability information from step 2 to |
| // sum up the non-phi use counts of all connected phis. |
| for (int i = 0; i < phi_count; ++i) { |
| HPhi* phi = phi_list->at(i); |
| for (BitVector::Iterator it(connected_phis[i]); |
| !it.Done(); |
| it.Advance()) { |
| int index = it.Current(); |
| HPhi* it_use = phi_list->at(index); |
| if (index != i) phi->AddNonPhiUsesFrom(it_use); // Don't count twice. |
| } |
| } |
| |
| // Initialize work list |
| for (int i = 0; i < graph()->blocks()->length(); ++i) { |
| HBasicBlock* block = graph()->blocks()->at(i); |
| const ZoneList<HPhi*>* phis = block->phis(); |
| for (int j = 0; j < phis->length(); ++j) { |
| AddToWorklist(phis->at(j)); |
| } |
| |
| for (HInstructionIterator it(block); !it.Done(); it.Advance()) { |
| HInstruction* current = it.Current(); |
| AddToWorklist(current); |
| } |
| } |
| |
| // Do a fixed point iteration, trying to improve representations |
| while (!worklist_.is_empty()) { |
| HValue* current = worklist_.RemoveLast(); |
| current->InferRepresentation(this); |
| in_worklist_.Remove(current->id()); |
| } |
| |
| // Lastly: any instruction that we don't have representation information |
| // for defaults to Tagged. |
| for (int i = 0; i < graph()->blocks()->length(); ++i) { |
| HBasicBlock* block = graph()->blocks()->at(i); |
| const ZoneList<HPhi*>* phis = block->phis(); |
| for (int j = 0; j < phis->length(); ++j) { |
| HPhi* phi = phis->at(j); |
| if (phi->representation().IsNone()) { |
| phi->ChangeRepresentation(Representation::Tagged()); |
| } |
| } |
| for (HInstructionIterator it(block); !it.Done(); it.Advance()) { |
| HInstruction* current = it.Current(); |
| if (current->representation().IsNone() && |
| current->CheckFlag(HInstruction::kFlexibleRepresentation)) { |
| if (current->CheckFlag(HInstruction::kCannotBeTagged)) { |
| current->ChangeRepresentation(Representation::Double()); |
| } else { |
| current->ChangeRepresentation(Representation::Tagged()); |
| } |
| } |
| } |
| } |
| } |
| |
| } // namespace internal |
| } // namespace v8 |