| // 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/hydrogen-representation-changes.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| void HRepresentationChangesPhase::InsertRepresentationChangeForUse( |
| HValue* value, HValue* use_value, int use_index, Representation to) { |
| // Insert the representation change right before its use. For phi-uses we |
| // insert at the end of the corresponding predecessor. |
| HInstruction* next = NULL; |
| if (use_value->IsPhi()) { |
| next = use_value->block()->predecessors()->at(use_index)->end(); |
| } else { |
| next = HInstruction::cast(use_value); |
| } |
| // For constants we try to make the representation change at compile |
| // time. When a representation change is not possible without loss of |
| // information we treat constants like normal instructions and insert the |
| // change instructions for them. |
| HInstruction* new_value = NULL; |
| bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi); |
| bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32); |
| if (value->IsConstant()) { |
| HConstant* constant = HConstant::cast(value); |
| // Try to create a new copy of the constant with the new representation. |
| if (is_truncating_to_int && to.IsInteger32()) { |
| Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone()); |
| if (res.has_value) new_value = res.value; |
| } else { |
| new_value = constant->CopyToRepresentation(to, graph()->zone()); |
| } |
| } |
| |
| if (new_value == NULL) { |
| new_value = new(graph()->zone()) HChange( |
| value, to, is_truncating_to_smi, is_truncating_to_int); |
| if (!use_value->operand_position(use_index).IsUnknown()) { |
| new_value->set_position(use_value->operand_position(use_index)); |
| } else { |
| DCHECK(!FLAG_hydrogen_track_positions || |
| !graph()->info()->IsOptimizing()); |
| } |
| } |
| |
| new_value->InsertBefore(next); |
| use_value->SetOperandAt(use_index, new_value); |
| } |
| |
| |
| static bool IsNonDeoptingIntToSmiChange(HChange* change) { |
| Representation from_rep = change->from(); |
| Representation to_rep = change->to(); |
| // Flags indicating Uint32 operations are set in a later Hydrogen phase. |
| DCHECK(!change->CheckFlag(HValue::kUint32)); |
| return from_rep.IsInteger32() && to_rep.IsSmi() && SmiValuesAre32Bits(); |
| } |
| |
| |
| void HRepresentationChangesPhase::InsertRepresentationChangesForValue( |
| HValue* value) { |
| Representation r = value->representation(); |
| if (r.IsNone()) return; |
| if (value->HasNoUses()) { |
| if (value->IsForceRepresentation()) value->DeleteAndReplaceWith(NULL); |
| return; |
| } |
| |
| for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) { |
| HValue* use_value = it.value(); |
| int use_index = it.index(); |
| Representation req = use_value->RequiredInputRepresentation(use_index); |
| if (req.IsNone() || req.Equals(r)) continue; |
| |
| // If this is an HForceRepresentation instruction, and an HChange has been |
| // inserted above it, examine the input representation of the HChange. If |
| // that's int32, and this HForceRepresentation use is int32, and int32 to |
| // smi changes can't cause deoptimisation, set the input of the use to the |
| // input of the HChange. |
| if (value->IsForceRepresentation()) { |
| HValue* input = HForceRepresentation::cast(value)->value(); |
| if (input->IsChange()) { |
| HChange* change = HChange::cast(input); |
| if (change->from().Equals(req) && IsNonDeoptingIntToSmiChange(change)) { |
| use_value->SetOperandAt(use_index, change->value()); |
| continue; |
| } |
| } |
| } |
| InsertRepresentationChangeForUse(value, use_value, use_index, req); |
| } |
| if (value->HasNoUses()) { |
| DCHECK(value->IsConstant() || value->IsForceRepresentation()); |
| value->DeleteAndReplaceWith(NULL); |
| } else { |
| // The only purpose of a HForceRepresentation is to represent the value |
| // after the (possible) HChange instruction. We make it disappear. |
| if (value->IsForceRepresentation()) { |
| value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value()); |
| } |
| } |
| } |
| |
| |
| void HRepresentationChangesPhase::Run() { |
| // Compute truncation flag for phis: Initially assume that all |
| // int32-phis allow truncation and iteratively remove the ones that |
| // are used in an operation that does not allow a truncating |
| // conversion. |
| ZoneList<HPhi*> int_worklist(8, zone()); |
| ZoneList<HPhi*> smi_worklist(8, zone()); |
| |
| const ZoneList<HPhi*>* phi_list(graph()->phi_list()); |
| for (int i = 0; i < phi_list->length(); i++) { |
| HPhi* phi = phi_list->at(i); |
| if (phi->representation().IsInteger32()) { |
| phi->SetFlag(HValue::kTruncatingToInt32); |
| } else if (phi->representation().IsSmi()) { |
| phi->SetFlag(HValue::kTruncatingToSmi); |
| phi->SetFlag(HValue::kTruncatingToInt32); |
| } |
| } |
| |
| for (int i = 0; i < phi_list->length(); i++) { |
| HPhi* phi = phi_list->at(i); |
| HValue* value = NULL; |
| if (phi->representation().IsSmiOrInteger32() && |
| !phi->CheckUsesForFlag(HValue::kTruncatingToInt32, &value)) { |
| int_worklist.Add(phi, zone()); |
| phi->ClearFlag(HValue::kTruncatingToInt32); |
| if (FLAG_trace_representation) { |
| PrintF("#%d Phi is not truncating Int32 because of #%d %s\n", |
| phi->id(), value->id(), value->Mnemonic()); |
| } |
| } |
| |
| if (phi->representation().IsSmi() && |
| !phi->CheckUsesForFlag(HValue::kTruncatingToSmi, &value)) { |
| smi_worklist.Add(phi, zone()); |
| phi->ClearFlag(HValue::kTruncatingToSmi); |
| if (FLAG_trace_representation) { |
| PrintF("#%d Phi is not truncating Smi because of #%d %s\n", |
| phi->id(), value->id(), value->Mnemonic()); |
| } |
| } |
| } |
| |
| while (!int_worklist.is_empty()) { |
| HPhi* current = int_worklist.RemoveLast(); |
| for (int i = 0; i < current->OperandCount(); ++i) { |
| HValue* input = current->OperandAt(i); |
| if (input->IsPhi() && |
| input->representation().IsSmiOrInteger32() && |
| input->CheckFlag(HValue::kTruncatingToInt32)) { |
| if (FLAG_trace_representation) { |
| PrintF("#%d Phi is not truncating Int32 because of #%d %s\n", |
| input->id(), current->id(), current->Mnemonic()); |
| } |
| input->ClearFlag(HValue::kTruncatingToInt32); |
| int_worklist.Add(HPhi::cast(input), zone()); |
| } |
| } |
| } |
| |
| while (!smi_worklist.is_empty()) { |
| HPhi* current = smi_worklist.RemoveLast(); |
| for (int i = 0; i < current->OperandCount(); ++i) { |
| HValue* input = current->OperandAt(i); |
| if (input->IsPhi() && |
| input->representation().IsSmi() && |
| input->CheckFlag(HValue::kTruncatingToSmi)) { |
| if (FLAG_trace_representation) { |
| PrintF("#%d Phi is not truncating Smi because of #%d %s\n", |
| input->id(), current->id(), current->Mnemonic()); |
| } |
| input->ClearFlag(HValue::kTruncatingToSmi); |
| smi_worklist.Add(HPhi::cast(input), zone()); |
| } |
| } |
| } |
| |
| const ZoneList<HBasicBlock*>* blocks(graph()->blocks()); |
| for (int i = 0; i < blocks->length(); ++i) { |
| // Process phi instructions first. |
| const HBasicBlock* block(blocks->at(i)); |
| const ZoneList<HPhi*>* phis = block->phis(); |
| for (int j = 0; j < phis->length(); j++) { |
| InsertRepresentationChangesForValue(phis->at(j)); |
| } |
| |
| // Process normal instructions. |
| for (HInstruction* current = block->first(); current != NULL; ) { |
| HInstruction* next = current->next(); |
| InsertRepresentationChangesForValue(current); |
| current = next; |
| } |
| } |
| } |
| |
| } } // namespace v8::internal |