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// Copyright 2023 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/objects/dependent-code.h"
#include "src/deoptimizer/deoptimizer.h"
#include "src/objects/allocation-site-inl.h"
#include "src/objects/dependent-code-inl.h"
#include "src/objects/map.h"
namespace v8 {
namespace internal {
Tagged<DependentCode> DependentCode::GetDependentCode(
Tagged<HeapObject> object) {
if (IsMap(object)) {
return Map::cast(object)->dependent_code();
} else if (IsPropertyCell(object)) {
return PropertyCell::cast(object)->dependent_code();
} else if (IsAllocationSite(object)) {
return AllocationSite::cast(object)->dependent_code();
}
UNREACHABLE();
}
void DependentCode::SetDependentCode(Handle<HeapObject> object,
Handle<DependentCode> dep) {
if (IsMap(*object)) {
Handle<Map>::cast(object)->set_dependent_code(*dep);
} else if (IsPropertyCell(*object)) {
Handle<PropertyCell>::cast(object)->set_dependent_code(*dep);
} else if (IsAllocationSite(*object)) {
Handle<AllocationSite>::cast(object)->set_dependent_code(*dep);
} else {
UNREACHABLE();
}
}
namespace {
void PrintDependencyGroups(DependentCode::DependencyGroups groups) {
while (groups != 0) {
auto group = static_cast<DependentCode::DependencyGroup>(
1 << base::bits::CountTrailingZeros(static_cast<uint32_t>(groups)));
StdoutStream{} << DependentCode::DependencyGroupName(group);
groups &= ~group;
if (groups != 0) StdoutStream{} << ",";
}
}
} // namespace
void DependentCode::InstallDependency(Isolate* isolate, Handle<Code> code,
Handle<HeapObject> object,
DependencyGroups groups) {
if (V8_UNLIKELY(v8_flags.trace_compilation_dependencies)) {
StdoutStream{} << "Installing dependency of [" << code << "] on [" << object
<< "] in groups [";
PrintDependencyGroups(groups);
StdoutStream{} << "]\n";
}
Handle<DependentCode> old_deps(DependentCode::GetDependentCode(*object),
isolate);
Handle<DependentCode> new_deps =
InsertWeakCode(isolate, old_deps, groups, code);
// Update the list head if necessary.
if (!new_deps.is_identical_to(old_deps)) {
DependentCode::SetDependentCode(object, new_deps);
}
}
Handle<DependentCode> DependentCode::InsertWeakCode(
Isolate* isolate, Handle<DependentCode> entries, DependencyGroups groups,
Handle<Code> code) {
if (entries->length() == entries->capacity()) {
// We'd have to grow - try to compact first.
entries->IterateAndCompact([](Code, DependencyGroups) { return false; });
}
MaybeObjectHandle code_slot(HeapObjectReference::Weak(*code), isolate);
entries = Handle<DependentCode>::cast(WeakArrayList::AddToEnd(
isolate, entries, code_slot, Smi::FromInt(groups)));
return entries;
}
void DependentCode::IterateAndCompact(const IterateAndCompactFn& fn) {
DisallowGarbageCollection no_gc;
int len = length();
if (len == 0) return;
// We compact during traversal, thus use a somewhat custom loop construct:
//
// - Loop back-to-front s.t. trailing cleared entries can simply drop off
// the back of the list.
// - Any cleared slots are filled from the back of the list.
int i = len - kSlotsPerEntry;
while (i >= 0) {
MaybeObject obj = Get(i + kCodeSlotOffset);
if (obj->IsCleared()) {
len = FillEntryFromBack(i, len);
i -= kSlotsPerEntry;
continue;
}
if (fn(Code::cast(obj.GetHeapObjectAssumeWeak()),
static_cast<DependencyGroups>(
Get(i + kGroupsSlotOffset).ToSmi().value()))) {
len = FillEntryFromBack(i, len);
}
i -= kSlotsPerEntry;
}
set_length(len);
}
bool DependentCode::MarkCodeForDeoptimization(
Isolate* isolate, DependentCode::DependencyGroups deopt_groups) {
DisallowGarbageCollection no_gc;
bool marked_something = false;
IterateAndCompact([&](Code code, DependencyGroups groups) {
if ((groups & deopt_groups) == 0) return false;
if (!code->marked_for_deoptimization()) {
code->SetMarkedForDeoptimization(isolate, "code dependencies");
marked_something = true;
}
return true;
});
return marked_something;
}
int DependentCode::FillEntryFromBack(int index, int length) {
DCHECK_EQ(index % 2, 0);
DCHECK_EQ(length % 2, 0);
for (int i = length - kSlotsPerEntry; i > index; i -= kSlotsPerEntry) {
MaybeObject obj = Get(i + kCodeSlotOffset);
if (obj->IsCleared()) continue;
Set(index + kCodeSlotOffset, obj);
Set(index + kGroupsSlotOffset, Get(i + kGroupsSlotOffset),
SKIP_WRITE_BARRIER);
return i;
}
return index; // No non-cleared entry found.
}
void DependentCode::DeoptimizeDependencyGroups(
Isolate* isolate, DependentCode::DependencyGroups groups) {
DisallowGarbageCollection no_gc_scope;
bool marked_something = MarkCodeForDeoptimization(isolate, groups);
if (marked_something) {
DCHECK(AllowCodeDependencyChange::IsAllowed());
Deoptimizer::DeoptimizeMarkedCode(isolate);
}
}
// static
Tagged<DependentCode> DependentCode::empty_dependent_code(
const ReadOnlyRoots& roots) {
return DependentCode::cast(roots.empty_weak_array_list());
}
const char* DependentCode::DependencyGroupName(DependencyGroup group) {
switch (group) {
case kTransitionGroup:
return "transition";
case kPrototypeCheckGroup:
return "prototype-check";
case kPropertyCellChangedGroup:
return "property-cell-changed";
case kFieldConstGroup:
return "field-const";
case kFieldTypeGroup:
return "field-type";
case kFieldRepresentationGroup:
return "field-representation";
case kInitialMapChangedGroup:
return "initial-map-changed";
case kAllocationSiteTenuringChangedGroup:
return "allocation-site-tenuring-changed";
case kAllocationSiteTransitionChangedGroup:
return "allocation-site-transition-changed";
}
UNREACHABLE();
}
} // namespace internal
} // namespace v8
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