v8/src/hydrogen-representation-changes.cc

193 lines
7.5 KiB
C++
Raw Normal View History

// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "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);
}
new_value->InsertBefore(next);
use_value->SetOperandAt(use_index, new_value);
}
void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
HValue* value) {
Representation r = value->representation();
if (r.IsNone()) return;
if (value->HasNoUses()) 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;
InsertRepresentationChangeForUse(value, use_value, use_index, req);
}
if (value->HasNoUses()) {
ASSERT(value->IsConstant());
value->DeleteAndReplaceWith(NULL);
}
// 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