[turbofan] Initial version of allocation folding and write barrier elimination.

src/compiler/change-lowering.cc

-// Copyright 2014 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/compiler/change-lowering.h"
-
-#include "src/compiler/js-graph.h"
-#include "src/compiler/linkage.h"
-#include "src/compiler/machine-operator.h"
-#include "src/compiler/node-properties.h"
-#include "src/compiler/simplified-operator.h"
-
-namespace v8 {
-namespace internal {
-namespace compiler {
-
-ChangeLowering::~ChangeLowering() {}
-
-
-Reduction ChangeLowering::Reduce(Node* node) {
-  switch (node->opcode()) {
-    case IrOpcode::kLoadField:
-      return ReduceLoadField(node);
-    case IrOpcode::kStoreField:
-      return ReduceStoreField(node);
-    case IrOpcode::kLoadElement:
-      return ReduceLoadElement(node);
-    case IrOpcode::kStoreElement:
-      return ReduceStoreElement(node);
-    case IrOpcode::kAllocate:
-      return ReduceAllocate(node);
-    default:
-      return NoChange();
-  }
-  UNREACHABLE();
-  return NoChange();
-}
-
-Reduction ChangeLowering::ReduceLoadField(Node* node) {
-  const FieldAccess& access = FieldAccessOf(node->op());
-  Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag());
-  node->InsertInput(graph()->zone(), 1, offset);
-  NodeProperties::ChangeOp(node, machine()->Load(access.machine_type));
-  return Changed(node);
-}
-
-Reduction ChangeLowering::ReduceStoreField(Node* node) {
-  const FieldAccess& access = FieldAccessOf(node->op());
-  Node* offset = jsgraph()->IntPtrConstant(access.offset - access.tag());
-  node->InsertInput(graph()->zone(), 1, offset);
-  NodeProperties::ChangeOp(node, machine()->Store(StoreRepresentation(
-                                     access.machine_type.representation(),
-                                     access.write_barrier_kind)));
-  return Changed(node);
-}
-
-
-Node* ChangeLowering::ComputeIndex(const ElementAccess& access,
-                                   Node* const key) {
-  Node* index = key;
-  const int element_size_shift =
-      ElementSizeLog2Of(access.machine_type.representation());
-  if (element_size_shift) {
-    index = graph()->NewNode(machine()->Word32Shl(), index,
-                             jsgraph()->Int32Constant(element_size_shift));
-  }
-  const int fixed_offset = access.header_size - access.tag();
-  if (fixed_offset) {
-    index = graph()->NewNode(machine()->Int32Add(), index,
-                             jsgraph()->Int32Constant(fixed_offset));
-  }
-  if (machine()->Is64()) {
-    // TODO(turbofan): This is probably only correct for typed arrays, and only
-    // if the typed arrays are at most 2GiB in size, which happens to match
-    // exactly our current situation.
-    index = graph()->NewNode(machine()->ChangeUint32ToUint64(), index);
-  }
-  return index;
-}
-
-Reduction ChangeLowering::ReduceLoadElement(Node* node) {
-  const ElementAccess& access = ElementAccessOf(node->op());
-  node->ReplaceInput(1, ComputeIndex(access, node->InputAt(1)));
-  NodeProperties::ChangeOp(node, machine()->Load(access.machine_type));
-  return Changed(node);
-}
-
-Reduction ChangeLowering::ReduceStoreElement(Node* node) {
-  const ElementAccess& access = ElementAccessOf(node->op());
-  node->ReplaceInput(1, ComputeIndex(access, node->InputAt(1)));
-  NodeProperties::ChangeOp(node, machine()->Store(StoreRepresentation(
-                                     access.machine_type.representation(),
-                                     access.write_barrier_kind)));
-  return Changed(node);
-}
-
-Reduction ChangeLowering::ReduceAllocate(Node* node) {
-  PretenureFlag const pretenure = OpParameter<PretenureFlag>(node->op());
-
-  Node* size = node->InputAt(0);
-  Node* effect = node->InputAt(1);
-  Node* control = node->InputAt(2);
-
-  if (machine()->Is64()) {
-    size = graph()->NewNode(machine()->ChangeInt32ToInt64(), size);
-  }
-
-  Node* top_address = jsgraph()->ExternalConstant(
-      pretenure == NOT_TENURED
-          ? ExternalReference::new_space_allocation_top_address(isolate())
-          : ExternalReference::old_space_allocation_top_address(isolate()));
-  Node* limit_address = jsgraph()->ExternalConstant(
-      pretenure == NOT_TENURED
-          ? ExternalReference::new_space_allocation_limit_address(isolate())
-          : ExternalReference::old_space_allocation_limit_address(isolate()));
-
-  Node* top = effect =
-      graph()->NewNode(machine()->Load(MachineType::Pointer()), top_address,
-                       jsgraph()->IntPtrConstant(0), effect, control);
-  Node* limit = effect =
-      graph()->NewNode(machine()->Load(MachineType::Pointer()), limit_address,
-                       jsgraph()->IntPtrConstant(0), effect, control);
-
-  Node* new_top = graph()->NewNode(machine()->IntAdd(), top, size);
-
-  Node* check = graph()->NewNode(machine()->UintLessThan(), new_top, limit);
-  Node* branch =
-      graph()->NewNode(common()->Branch(BranchHint::kTrue), check, control);
-
-  Node* if_true = graph()->NewNode(common()->IfTrue(), branch);
-  Node* etrue = effect;
-  Node* vtrue;
-  {
-    etrue = graph()->NewNode(
-        machine()->Store(StoreRepresentation(
-            MachineType::PointerRepresentation(), kNoWriteBarrier)),
-        top_address, jsgraph()->IntPtrConstant(0), new_top, etrue, if_true);
-    vtrue = graph()->NewNode(
-        machine()->BitcastWordToTagged(),
-        graph()->NewNode(machine()->IntAdd(), top,
-                         jsgraph()->IntPtrConstant(kHeapObjectTag)));
-  }
-
-  Node* if_false = graph()->NewNode(common()->IfFalse(), branch);
-  Node* efalse = effect;
-  Node* vfalse;
-  {
-    Node* target = pretenure == NOT_TENURED
-                       ? jsgraph()->AllocateInNewSpaceStubConstant()
-                       : jsgraph()->AllocateInOldSpaceStubConstant();
-    if (!allocate_operator_.is_set()) {
-      CallDescriptor* descriptor =
-          Linkage::GetAllocateCallDescriptor(graph()->zone());
-      allocate_operator_.set(common()->Call(descriptor));
-    }
-    vfalse = efalse = graph()->NewNode(allocate_operator_.get(), target, size,
-                                       efalse, if_false);
-  }
-
-  control = graph()->NewNode(common()->Merge(2), if_true, if_false);
-  effect = graph()->NewNode(common()->EffectPhi(2), etrue, efalse, control);
-  Node* value = graph()->NewNode(
-      common()->Phi(MachineRepresentation::kTagged, 2), vtrue, vfalse, control);
-
-  ReplaceWithValue(node, value, effect);
-  return Replace(value);
-}
-
-Isolate* ChangeLowering::isolate() const { return jsgraph()->isolate(); }
-
-
-Graph* ChangeLowering::graph() const { return jsgraph()->graph(); }
-
-
-CommonOperatorBuilder* ChangeLowering::common() const {
-  return jsgraph()->common();
-}
-
-
-MachineOperatorBuilder* ChangeLowering::machine() const {
-  return jsgraph()->machine();
-}
-
-}  // namespace compiler
-}  // namespace internal
-}  // namespace v8