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213 lines
7.8 KiB
213 lines
7.8 KiB
// Copyright 2013 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "src/hydrogen-representation-changes.h"
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namespace v8 {
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namespace internal {
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void HRepresentationChangesPhase::InsertRepresentationChangeForUse(
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HValue* value, HValue* use_value, int use_index, Representation to) {
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// Insert the representation change right before its use. For phi-uses we
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// insert at the end of the corresponding predecessor.
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HInstruction* next = NULL;
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if (use_value->IsPhi()) {
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next = use_value->block()->predecessors()->at(use_index)->end();
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} else {
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next = HInstruction::cast(use_value);
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}
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// For constants we try to make the representation change at compile
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// time. When a representation change is not possible without loss of
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// information we treat constants like normal instructions and insert the
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// change instructions for them.
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HInstruction* new_value = NULL;
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bool is_truncating_to_smi = use_value->CheckFlag(HValue::kTruncatingToSmi);
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bool is_truncating_to_int = use_value->CheckFlag(HValue::kTruncatingToInt32);
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if (value->IsConstant()) {
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HConstant* constant = HConstant::cast(value);
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// Try to create a new copy of the constant with the new representation.
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if (is_truncating_to_int && to.IsInteger32()) {
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Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone());
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if (res.has_value) new_value = res.value;
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} else {
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new_value = constant->CopyToRepresentation(to, graph()->zone());
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}
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}
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if (new_value == NULL) {
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new_value = new(graph()->zone()) HChange(
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value, to, is_truncating_to_smi, is_truncating_to_int);
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if (!use_value->operand_position(use_index).IsUnknown()) {
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new_value->set_position(use_value->operand_position(use_index));
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} else {
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DCHECK(!FLAG_hydrogen_track_positions ||
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!graph()->info()->IsOptimizing());
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}
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}
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new_value->InsertBefore(next);
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use_value->SetOperandAt(use_index, new_value);
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}
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static bool IsNonDeoptingIntToSmiChange(HChange* change) {
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Representation from_rep = change->from();
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Representation to_rep = change->to();
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// Flags indicating Uint32 operations are set in a later Hydrogen phase.
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DCHECK(!change->CheckFlag(HValue::kUint32));
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return from_rep.IsInteger32() && to_rep.IsSmi() && SmiValuesAre32Bits();
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}
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void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
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HValue* value) {
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Representation r = value->representation();
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if (r.IsNone()) {
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#ifdef DEBUG
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for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
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HValue* use_value = it.value();
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int use_index = it.index();
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Representation req = use_value->RequiredInputRepresentation(use_index);
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DCHECK(req.IsNone());
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}
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#endif
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return;
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}
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if (value->HasNoUses()) {
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if (value->IsForceRepresentation()) value->DeleteAndReplaceWith(NULL);
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return;
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}
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for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
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HValue* use_value = it.value();
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int use_index = it.index();
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Representation req = use_value->RequiredInputRepresentation(use_index);
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if (req.IsNone() || req.Equals(r)) continue;
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// If this is an HForceRepresentation instruction, and an HChange has been
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// inserted above it, examine the input representation of the HChange. If
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// that's int32, and this HForceRepresentation use is int32, and int32 to
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// smi changes can't cause deoptimisation, set the input of the use to the
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// input of the HChange.
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if (value->IsForceRepresentation()) {
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HValue* input = HForceRepresentation::cast(value)->value();
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if (input->IsChange()) {
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HChange* change = HChange::cast(input);
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if (change->from().Equals(req) && IsNonDeoptingIntToSmiChange(change)) {
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use_value->SetOperandAt(use_index, change->value());
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continue;
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}
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}
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}
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InsertRepresentationChangeForUse(value, use_value, use_index, req);
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}
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if (value->HasNoUses()) {
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DCHECK(value->IsConstant() || value->IsForceRepresentation());
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value->DeleteAndReplaceWith(NULL);
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} else {
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// The only purpose of a HForceRepresentation is to represent the value
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// after the (possible) HChange instruction. We make it disappear.
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if (value->IsForceRepresentation()) {
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value->DeleteAndReplaceWith(HForceRepresentation::cast(value)->value());
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}
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}
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}
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void HRepresentationChangesPhase::Run() {
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// Compute truncation flag for phis: Initially assume that all
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// int32-phis allow truncation and iteratively remove the ones that
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// are used in an operation that does not allow a truncating
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// conversion.
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ZoneList<HPhi*> int_worklist(8, zone());
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ZoneList<HPhi*> smi_worklist(8, zone());
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const ZoneList<HPhi*>* phi_list(graph()->phi_list());
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for (int i = 0; i < phi_list->length(); i++) {
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HPhi* phi = phi_list->at(i);
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if (phi->representation().IsInteger32()) {
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phi->SetFlag(HValue::kTruncatingToInt32);
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} else if (phi->representation().IsSmi()) {
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phi->SetFlag(HValue::kTruncatingToSmi);
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phi->SetFlag(HValue::kTruncatingToInt32);
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}
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}
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for (int i = 0; i < phi_list->length(); i++) {
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HPhi* phi = phi_list->at(i);
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HValue* value = NULL;
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if (phi->representation().IsSmiOrInteger32() &&
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!phi->CheckUsesForFlag(HValue::kTruncatingToInt32, &value)) {
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int_worklist.Add(phi, zone());
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phi->ClearFlag(HValue::kTruncatingToInt32);
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if (FLAG_trace_representation) {
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PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
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phi->id(), value->id(), value->Mnemonic());
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}
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}
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if (phi->representation().IsSmi() &&
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!phi->CheckUsesForFlag(HValue::kTruncatingToSmi, &value)) {
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smi_worklist.Add(phi, zone());
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phi->ClearFlag(HValue::kTruncatingToSmi);
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if (FLAG_trace_representation) {
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PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
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phi->id(), value->id(), value->Mnemonic());
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}
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}
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}
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while (!int_worklist.is_empty()) {
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HPhi* current = int_worklist.RemoveLast();
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for (int i = 0; i < current->OperandCount(); ++i) {
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HValue* input = current->OperandAt(i);
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if (input->IsPhi() &&
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input->representation().IsSmiOrInteger32() &&
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input->CheckFlag(HValue::kTruncatingToInt32)) {
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if (FLAG_trace_representation) {
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PrintF("#%d Phi is not truncating Int32 because of #%d %s\n",
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input->id(), current->id(), current->Mnemonic());
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}
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input->ClearFlag(HValue::kTruncatingToInt32);
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int_worklist.Add(HPhi::cast(input), zone());
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}
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}
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}
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while (!smi_worklist.is_empty()) {
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HPhi* current = smi_worklist.RemoveLast();
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for (int i = 0; i < current->OperandCount(); ++i) {
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HValue* input = current->OperandAt(i);
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if (input->IsPhi() &&
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input->representation().IsSmi() &&
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input->CheckFlag(HValue::kTruncatingToSmi)) {
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if (FLAG_trace_representation) {
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PrintF("#%d Phi is not truncating Smi because of #%d %s\n",
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input->id(), current->id(), current->Mnemonic());
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}
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input->ClearFlag(HValue::kTruncatingToSmi);
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smi_worklist.Add(HPhi::cast(input), zone());
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}
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}
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}
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const ZoneList<HBasicBlock*>* blocks(graph()->blocks());
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for (int i = 0; i < blocks->length(); ++i) {
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// Process phi instructions first.
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const HBasicBlock* block(blocks->at(i));
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const ZoneList<HPhi*>* phis = block->phis();
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for (int j = 0; j < phis->length(); j++) {
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InsertRepresentationChangesForValue(phis->at(j));
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}
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// Process normal instructions.
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for (HInstruction* current = block->first(); current != NULL; ) {
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HInstruction* next = current->next();
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InsertRepresentationChangesForValue(current);
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current = next;
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}
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}
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}
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} } // namespace v8::internal
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