Compiler changes for bitstring based type checks.
We guard the use of this feature with a compile-time flag,
set to true in this CL.
Boot image size for aosp_taimen-userdebug in AOSP master:
- before:
arm boot*.oat: 63604740
arm64 boot*.oat: 74237864
- after:
arm boot*.oat: 63531172 (-72KiB, -0.1%)
arm64 boot*.oat: 74135008 (-100KiB, -0.1%)
The new TypeCheckBenchmark yields the following changes
using the little cores of taimen fixed at 1.4016GHz:
32-bit 64-bit
timeCheckCastLevel1ToLevel1 11.48->15.80 11.47->15.78
timeCheckCastLevel2ToLevel1 15.08->15.79 15.08->15.79
timeCheckCastLevel3ToLevel1 19.01->15.82 17.94->15.81
timeCheckCastLevel9ToLevel1 42.55->15.79 42.63->15.81
timeCheckCastLevel9ToLevel2 39.70->14.36 39.70->14.35
timeInstanceOfLevel1ToLevel1 13.74->17.93 13.76->17.95
timeInstanceOfLevel2ToLevel1 17.02->17.95 16.99->17.93
timeInstanceOfLevel3ToLevel1 24.03->17.95 24.45->17.95
timeInstanceOfLevel9ToLevel1 47.13->17.95 47.14->18.00
timeInstanceOfLevel9ToLevel2 44.19->16.52 44.27->16.51
This suggests that the bitstring typecheck should not be
used for exact type checks which would be equivalent to the
"Level1ToLevel1" benchmark. Whether the implementation is
a beneficial replacement for the kClassHierarchyCheck and
kAbstractClassCheck on average depends on how many levels
from the target class (or Object for a negative result) is
a typical object's class.
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing --jit
Test: testrunner.py --host -t 670-bitstring-type-check
Test: Pixel 2 XL boots.
Test: testrunner.py --target --optimizing --jit
Test: testrunner.py --target -t 670-bitstring-type-check
Bug: 64692057
Bug: 71853552
Bug: 26687569
Change-Id: I538d7e036b5a8ae2cc3fe77662a5903d74854562
diff --git a/compiler/optimizing/instruction_builder.cc b/compiler/optimizing/instruction_builder.cc
index 64a1ecc..0205c6a 100644
--- a/compiler/optimizing/instruction_builder.cc
+++ b/compiler/optimizing/instruction_builder.cc
@@ -1811,29 +1811,6 @@
}
}
-static TypeCheckKind ComputeTypeCheckKind(Handle<mirror::Class> cls)
- REQUIRES_SHARED(Locks::mutator_lock_) {
- if (cls == nullptr) {
- return TypeCheckKind::kUnresolvedCheck;
- } else if (cls->IsInterface()) {
- return TypeCheckKind::kInterfaceCheck;
- } else if (cls->IsArrayClass()) {
- if (cls->GetComponentType()->IsObjectClass()) {
- return TypeCheckKind::kArrayObjectCheck;
- } else if (cls->CannotBeAssignedFromOtherTypes()) {
- return TypeCheckKind::kExactCheck;
- } else {
- return TypeCheckKind::kArrayCheck;
- }
- } else if (cls->IsFinal()) {
- return TypeCheckKind::kExactCheck;
- } else if (cls->IsAbstract()) {
- return TypeCheckKind::kAbstractClassCheck;
- } else {
- return TypeCheckKind::kClassHierarchyCheck;
- }
-}
-
void HInstructionBuilder::BuildLoadString(dex::StringIndex string_index, uint32_t dex_pc) {
HLoadString* load_string =
new (allocator_) HLoadString(graph_->GetCurrentMethod(), string_index, *dex_file_, dex_pc);
@@ -1848,22 +1825,8 @@
HLoadClass* HInstructionBuilder::BuildLoadClass(dex::TypeIndex type_index, uint32_t dex_pc) {
ScopedObjectAccess soa(Thread::Current());
const DexFile& dex_file = *dex_compilation_unit_->GetDexFile();
- Handle<mirror::ClassLoader> class_loader = dex_compilation_unit_->GetClassLoader();
- Handle<mirror::Class> klass = handles_->NewHandle(compiler_driver_->ResolveClass(
- soa, dex_compilation_unit_->GetDexCache(), class_loader, type_index, dex_compilation_unit_));
-
- bool needs_access_check = true;
- if (klass != nullptr) {
- if (klass->IsPublic()) {
- needs_access_check = false;
- } else {
- ObjPtr<mirror::Class> compiling_class = GetCompilingClass();
- if (compiling_class != nullptr && compiling_class->CanAccess(klass.Get())) {
- needs_access_check = false;
- }
- }
- }
-
+ Handle<mirror::Class> klass = ResolveClass(soa, type_index);
+ bool needs_access_check = LoadClassNeedsAccessCheck(klass);
return BuildLoadClass(type_index, dex_file, klass, dex_pc, needs_access_check);
}
@@ -1908,25 +1871,83 @@
return load_class;
}
+Handle<mirror::Class> HInstructionBuilder::ResolveClass(ScopedObjectAccess& soa,
+ dex::TypeIndex type_index) {
+ Handle<mirror::ClassLoader> class_loader = dex_compilation_unit_->GetClassLoader();
+ ObjPtr<mirror::Class> klass = compiler_driver_->ResolveClass(
+ soa, dex_compilation_unit_->GetDexCache(), class_loader, type_index, dex_compilation_unit_);
+ // TODO: Avoid creating excessive handles if the method references the same class repeatedly.
+ // (Use a map on the local_allocator_.)
+ return handles_->NewHandle(klass);
+}
+
+bool HInstructionBuilder::LoadClassNeedsAccessCheck(Handle<mirror::Class> klass) {
+ if (klass == nullptr) {
+ return true;
+ } else if (klass->IsPublic()) {
+ return false;
+ } else {
+ ObjPtr<mirror::Class> compiling_class = GetCompilingClass();
+ return compiling_class == nullptr || !compiling_class->CanAccess(klass.Get());
+ }
+}
+
void HInstructionBuilder::BuildTypeCheck(const Instruction& instruction,
uint8_t destination,
uint8_t reference,
dex::TypeIndex type_index,
uint32_t dex_pc) {
HInstruction* object = LoadLocal(reference, DataType::Type::kReference);
- HLoadClass* cls = BuildLoadClass(type_index, dex_pc);
ScopedObjectAccess soa(Thread::Current());
- TypeCheckKind check_kind = ComputeTypeCheckKind(cls->GetClass());
+ const DexFile& dex_file = *dex_compilation_unit_->GetDexFile();
+ Handle<mirror::Class> klass = ResolveClass(soa, type_index);
+ bool needs_access_check = LoadClassNeedsAccessCheck(klass);
+ TypeCheckKind check_kind = HSharpening::ComputeTypeCheckKind(
+ klass.Get(), code_generator_, compiler_driver_, needs_access_check);
+
+ HInstruction* class_or_null = nullptr;
+ HIntConstant* bitstring_path_to_root = nullptr;
+ HIntConstant* bitstring_mask = nullptr;
+ if (check_kind == TypeCheckKind::kBitstringCheck) {
+ // TODO: Allow using the bitstring check also if we need an access check.
+ DCHECK(!needs_access_check);
+ class_or_null = graph_->GetNullConstant(dex_pc);
+ MutexLock subtype_check_lock(Thread::Current(), *Locks::subtype_check_lock_);
+ uint32_t path_to_root =
+ SubtypeCheck<ObjPtr<mirror::Class>>::GetEncodedPathToRootForTarget(klass.Get());
+ uint32_t mask = SubtypeCheck<ObjPtr<mirror::Class>>::GetEncodedPathToRootMask(klass.Get());
+ bitstring_path_to_root = graph_->GetIntConstant(static_cast<int32_t>(path_to_root), dex_pc);
+ bitstring_mask = graph_->GetIntConstant(static_cast<int32_t>(mask), dex_pc);
+ } else {
+ class_or_null = BuildLoadClass(type_index, dex_file, klass, dex_pc, needs_access_check);
+ }
+ DCHECK(class_or_null != nullptr);
+
if (instruction.Opcode() == Instruction::INSTANCE_OF) {
- AppendInstruction(new (allocator_) HInstanceOf(object, cls, check_kind, dex_pc));
+ AppendInstruction(new (allocator_) HInstanceOf(object,
+ class_or_null,
+ check_kind,
+ klass,
+ dex_pc,
+ allocator_,
+ bitstring_path_to_root,
+ bitstring_mask));
UpdateLocal(destination, current_block_->GetLastInstruction());
} else {
DCHECK_EQ(instruction.Opcode(), Instruction::CHECK_CAST);
// We emit a CheckCast followed by a BoundType. CheckCast is a statement
// which may throw. If it succeeds BoundType sets the new type of `object`
// for all subsequent uses.
- AppendInstruction(new (allocator_) HCheckCast(object, cls, check_kind, dex_pc));
+ AppendInstruction(
+ new (allocator_) HCheckCast(object,
+ class_or_null,
+ check_kind,
+ klass,
+ dex_pc,
+ allocator_,
+ bitstring_path_to_root,
+ bitstring_mask));
AppendInstruction(new (allocator_) HBoundType(object, dex_pc));
UpdateLocal(reference, current_block_->GetLastInstruction());
}