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// Copyright 2022 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/heap/conservative-stack-visitor.h"
#include "test/unittests/heap/heap-utils.h"
#include "test/unittests/test-utils.h"
namespace v8 {
namespace internal {
namespace {
class RecordingVisitor final : public RootVisitor {
public:
V8_NOINLINE explicit RecordingVisitor(Isolate* isolate) {
// Allocate the object.
auto h = isolate->factory()->NewFixedArray(256, AllocationType::kOld);
the_object_ = h->GetHeapObject();
base_address_ = the_object_.address();
tagged_address_ = the_object_.ptr();
inner_address_ = base_address_ + 42 * kTaggedSize;
#ifdef V8_COMPRESS_POINTERS
compr_address_ = static_cast<uint32_t>(
V8HeapCompressionScheme::CompressTagged(base_address_));
compr_inner_ = static_cast<uint32_t>(
V8HeapCompressionScheme::CompressTagged(inner_address_));
#else
compr_address_ = static_cast<uint32_t>(base_address_);
compr_inner_ = static_cast<uint32_t>(inner_address_);
#endif
}
void VisitRootPointers(Root root, const char* description,
FullObjectSlot start, FullObjectSlot end) override {
for (FullObjectSlot current = start; current != end; ++current) {
if (*current == the_object_) found_ = true;
}
}
void Reset() { found_ = false; }
bool found() const { return found_; }
Address base_address() const { return base_address_; }
Address tagged_address() const { return tagged_address_; }
Address inner_address() const { return inner_address_; }
uint32_t compr_address() const { return compr_address_; }
uint32_t compr_inner() const { return compr_inner_; }
private:
// Some heap object that we want to check if it is visited or not.
HeapObject the_object_;
// Addresses of this object.
Address base_address_; // Uncompressed base address
Address tagged_address_; // Tagged uncompressed base address
Address inner_address_; // Some inner address
uint32_t compr_address_; // Compressed base address
uint32_t compr_inner_; // Compressed inner address
// Has the object been found?
bool found_ = false;
};
} // namespace
using ConservativeStackVisitorTest = TestWithHeapInternalsAndContext;
// In the following, we avoid negative tests, i.e., tests checking that objects
// are not visited when there are no pointers to them on the stack. Such tests
// are generally fragile and could fail on some platforms because of unforeseen
// compiler optimizations. In general we cannot ensure in a portable way that
// no pointer remained on the stack (or in some register) after the
// initialization of RecordingVisitor and until the invocation of
// Stack::IteratePointers.
TEST_F(ConservativeStackVisitorTest, DirectBasePointer) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile Address ptr = recorder->base_address();
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(kNullAddress, ptr);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
TEST_F(ConservativeStackVisitorTest, TaggedBasePointer) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile Address ptr = recorder->tagged_address();
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(kNullAddress, ptr);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
TEST_F(ConservativeStackVisitorTest, InnerPointer) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile Address ptr = recorder->inner_address();
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(kNullAddress, ptr);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
#ifdef V8_COMPRESS_POINTERS
TEST_F(ConservativeStackVisitorTest, HalfWord1) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile uint32_t ptr[] = {recorder->compr_address(), 0};
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(static_cast<uint32_t>(0), ptr[0]);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
TEST_F(ConservativeStackVisitorTest, HalfWord2) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile uint32_t ptr[] = {0, recorder->compr_address()};
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(static_cast<uint32_t>(0), ptr[1]);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
TEST_F(ConservativeStackVisitorTest, InnerHalfWord1) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile uint32_t ptr[] = {recorder->compr_inner(), 0};
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(static_cast<uint32_t>(0), ptr[0]);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
TEST_F(ConservativeStackVisitorTest, InnerHalfWord2) {
auto recorder = std::make_unique<RecordingVisitor>(isolate());
// Ensure the heap is iterable before CSS.
IsolateSafepointScope safepoint_scope(heap());
heap()->MakeHeapIterable();
{
volatile uint32_t ptr[] = {0, recorder->compr_inner()};
ConservativeStackVisitor stack_visitor(isolate(), recorder.get());
isolate()->heap()->stack().IteratePointers(&stack_visitor);
// Make sure to keep the pointer alive.
EXPECT_NE(static_cast<uint32_t>(0), ptr[1]);
}
// The object should have been visited.
EXPECT_TRUE(recorder->found());
}
#endif // V8_COMPRESS_POINTERS
} // namespace internal
} // namespace v8
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