[wasm-hints] Enabled Lazy Compilation by Hint

Hints for lazy compilation are now taken into consideration. If the
custom hints section suggests lazy compilatin we do so unless the module
consists of a single function.

Bug: v8:9003
Change-Id: Ibdc400453cee20d4d5c814733887b38fb675b220
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1535827
Commit-Queue: Frederik Gossen <frgossen@google.com>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60557}

src/compiler/wasm-compiler.cc

@@ -5948,7 +5948,7 @@ wasm::WasmCode* CompileWasmMathIntrinsic(wasm::WasmEngine* wasm_engine,
       std::move(result.source_positions), wasm::WasmCode::kFunction,
       wasm::WasmCode::kOther);
   // TODO(titzer): add counters for math intrinsic code size / allocation
-  return native_module->PublishCode(std::move(wasm_code));
+  return native_module->PublishCode(std::move(wasm_code)).code;
 }
 
 wasm::WasmCode* CompileWasmImportCallWrapper(wasm::WasmEngine* wasm_engine,
@@ -6012,7 +6012,7 @@ wasm::WasmCode* CompileWasmImportCallWrapper(wasm::WasmEngine* wasm_engine,
       std::move(result.protected_instructions),
       std::move(result.source_positions), wasm::WasmCode::kWasmToJsWrapper,
       wasm::WasmCode::kOther);
-  return native_module->PublishCode(std::move(wasm_code));
+  return native_module->PublishCode(std::move(wasm_code)).code;
 }
 
 wasm::WasmCompilationResult CompileWasmInterpreterEntry(
@@ -6243,7 +6243,9 @@ wasm::WasmCompilationResult TurbofanWasmCompilationUnit::ExecuteCompilation(
   // TODO(bradnelson): Improve histogram handling of size_t.
   counters->wasm_compile_function_peak_memory_bytes()->AddSample(
       static_cast<int>(mcgraph->graph()->zone()->allocation_size()));
-  return std::move(*info.ReleaseWasmCompilationResult());
+  auto result = info.ReleaseWasmCompilationResult();
+  DCHECK_EQ(wasm::ExecutionTier::kOptimized, result->result_tier);
+  return std::move(*result);
 }
 
 wasm::WasmCompilationResult InterpreterCompilationUnit::ExecuteCompilation(
@@ -6260,6 +6262,7 @@ wasm::WasmCompilationResult InterpreterCompilationUnit::ExecuteCompilation(
       wasm_unit_->wasm_engine_, env->enabled_features, wasm_unit_->func_index_,
       func_body.sig);
   DCHECK(result.succeeded());
+  DCHECK_EQ(wasm::ExecutionTier::kInterpreter, result.result_tier);
 
   return result;
 }

src/wasm/compilation-environment.h

@@ -21,6 +21,7 @@ namespace wasm {
 
 class NativeModule;
 class WasmCode;
+struct WasmCompilationResult;
 class WasmError;
 
 enum RuntimeExceptionSupport : bool {
@@ -120,7 +121,8 @@ class CompilationState {
 
   bool failed() const;
 
-  void OnFinishedUnit(ExecutionTier, WasmCode*);
+  void FinishUnit(WasmCompilationResult);
+  void FinishUnits(Vector<WasmCompilationResult>);
 
  private:
   friend class NativeModule;

src/wasm/function-compiler.h

@@ -52,6 +52,7 @@ struct WasmCompilationResult {
   MOVE_ONLY_WITH_DEFAULT_CONSTRUCTORS(WasmCompilationResult);
 
   bool succeeded() const { return code_desc.buffer != nullptr; }
+  bool failed() const { return !succeeded(); }
   operator bool() const { return succeeded(); }
 
   CodeDesc code_desc;

src/wasm/module-decoder.cc

@@ -1008,7 +1008,10 @@ class ModuleDecoderImpl : public Decoder {
     }
 
     // Decode sequence of compilation hints.
-    if (decoder.ok()) module_->compilation_hints.reserve(hint_count);
+    if (decoder.ok()) {
+      module_->compilation_hints.reserve(hint_count);
+      module_->num_lazy_compilation_hints = 0;
+    }
     for (uint32_t i = 0; decoder.ok() && i < hint_count; i++) {
       TRACE("DecodeCompilationHints[%d] module+%d\n", i,
             static_cast<int>(pc_ - start_));
@@ -1047,12 +1050,18 @@ class ModuleDecoderImpl : public Decoder {
       }
 
       // Happily accept compilation hint.
-      if (decoder.ok()) module_->compilation_hints.push_back(std::move(hint));
+      if (decoder.ok()) {
+        if (hint.strategy == WasmCompilationHintStrategy::kLazy) {
+          module_->num_lazy_compilation_hints++;
+        }
+        module_->compilation_hints.push_back(std::move(hint));
+      }
     }
 
     // If section was invalid reset compilation hints.
     if (decoder.failed()) {
       module_->compilation_hints.clear();
+      module_->num_lazy_compilation_hints = 0;
     }
 
     // @TODO(frgossen) Skip the whole compilation hints section in the outer

src/wasm/wasm-code-manager.cc

@@ -433,19 +433,25 @@ WasmCode* NativeModule::AddCodeForTesting(Handle<Code> code) {
   return AddAndPublishAnonymousCode(code, WasmCode::kFunction);
 }
 
-void NativeModule::SetLazyBuiltin() {
-  uint32_t num_wasm_functions = module_->num_declared_functions;
-  if (num_wasm_functions == 0) return;
-  // Fill the jump table with jumps to the lazy compile stub.
-  Address lazy_compile_target = runtime_stub_entry(WasmCode::kWasmCompileLazy);
-  for (uint32_t i = 0; i < num_wasm_functions; ++i) {
-    JumpTableAssembler::EmitLazyCompileJumpSlot(
-        jump_table_->instruction_start(), i,
-        i + module_->num_imported_functions, lazy_compile_target,
-        WasmCode::kNoFlushICache);
+void NativeModule::UseLazyStubs() {
+  uint32_t start = module_->num_imported_functions;
+  uint32_t end = start + module_->num_declared_functions;
+  for (uint32_t func_index = start; func_index < end; func_index++) {
+    UseLazyStub(func_index);
   }
-  FlushInstructionCache(jump_table_->instructions().start(),
-                        jump_table_->instructions().size());
+}
+
+void NativeModule::UseLazyStub(uint32_t func_index) {
+  DCHECK_LE(module_->num_imported_functions, func_index);
+  DCHECK_LT(func_index,
+            module_->num_imported_functions + module_->num_declared_functions);
+
+  // Add jump table entry for jump to the lazy compile stub.
+  uint32_t slot_index = func_index - module_->num_imported_functions;
+  DCHECK_NE(runtime_stub_entry(WasmCode::kWasmCompileLazy), kNullAddress);
+  JumpTableAssembler::EmitLazyCompileJumpSlot(
+      jump_table_->instruction_start(), slot_index, func_index,
+      runtime_stub_entry(WasmCode::kWasmCompileLazy), WasmCode::kFlushICache);
 }
 
 // TODO(mstarzinger): Remove {Isolate} parameter once {V8_EMBEDDED_BUILTINS}
@@ -581,7 +587,7 @@ WasmCode* NativeModule::AddAndPublishAnonymousCode(Handle<Code> code,
   new_code->MaybePrint(name);
   new_code->Validate();
 
-  return PublishCode(std::move(new_code));
+  return PublishCode(std::move(new_code)).code;
 }
 
 std::unique_ptr<WasmCode> NativeModule::AddCode(
@@ -667,39 +673,98 @@ std::unique_ptr<WasmCode> NativeModule::AddCodeWithCodeSpace(
   return code;
 }
 
-WasmCode* NativeModule::PublishCode(std::unique_ptr<WasmCode> code) {
+WasmCodeUpdate NativeModule::PublishCode(std::unique_ptr<WasmCode> code) {
   base::MutexGuard lock(&allocation_mutex_);
   return PublishCodeLocked(std::move(code));
 }
 
-WasmCode* NativeModule::PublishCodeLocked(std::unique_ptr<WasmCode> code) {
+namespace {
+WasmCode::Tier GetCodeTierForExecutionTier(ExecutionTier tier) {
+  switch (tier) {
+    case ExecutionTier::kInterpreter:
+      return WasmCode::Tier::kOther;
+    case ExecutionTier::kBaseline:
+      return WasmCode::Tier::kLiftoff;
+    case ExecutionTier::kOptimized:
+      return WasmCode::Tier::kTurbofan;
+  }
+}
+
+WasmCode::Kind GetCodeKindForExecutionTier(ExecutionTier tier) {
+  switch (tier) {
+    case ExecutionTier::kInterpreter:
+      return WasmCode::Kind::kInterpreterEntry;
+    case ExecutionTier::kBaseline:
+    case ExecutionTier::kOptimized:
+      return WasmCode::Kind::kFunction;
+  }
+}
+
+// TODO(frgossen): We should merge ExecutionTier with WasmCode::Tier.
+base::Optional<ExecutionTier> GetExecutionTier(WasmCode* code) {
+  if (code == nullptr) return {};
+  switch (code->tier()) {
+    case WasmCode::Tier::kLiftoff:
+      DCHECK_EQ(code->kind(), WasmCode::Kind::kFunction);
+      return ExecutionTier::kBaseline;
+    case WasmCode::Tier::kTurbofan:
+      DCHECK_EQ(code->kind(), WasmCode::Kind::kFunction);
+      return ExecutionTier::kOptimized;
+    case WasmCode::Tier::kOther:
+      if (code->kind() == WasmCode::Kind::kInterpreterEntry)
+        return ExecutionTier::kInterpreter;
+      return {};
+  }
+  UNREACHABLE();
+}
+}  // namespace
+
+WasmCodeUpdate NativeModule::PublishCodeLocked(std::unique_ptr<WasmCode> code) {
   // The caller must hold the {allocation_mutex_}, thus we fail to lock it here.
   DCHECK(!allocation_mutex_.TryLock());
+  base::Optional<ExecutionTier> prior_tier;
+  base::Optional<ExecutionTier> tier;
   // Skip publishing code if there is an active redirection to the interpreter
   // for the given function index, in order to preserve the redirection.
   if (!code->IsAnonymous() && !has_interpreter_redirection(code->index())) {
     DCHECK_LT(code->index(), num_functions());
     DCHECK_LE(module_->num_imported_functions, code->index());
 
-    // Update code table, except for interpreter entries that would overwrite
-    // existing code.
+    // Assume an order of execution tiers that represents the quality of their
+    // generated code.
+    static_assert(ExecutionTier::kInterpreter < ExecutionTier::kBaseline &&
+                      ExecutionTier::kBaseline < ExecutionTier::kOptimized,
+                  "Assume an order on execution tiers");
+
+    // Update code table but avoid to fall back to less optimized code. We use
+    // the new code if it was compiled with a higher tier and also if we cannot
+    // determine the tier.
     uint32_t slot_idx = code->index() - module_->num_imported_functions;
-    if (code->kind() != WasmCode::kInterpreterEntry ||
-        code_table_[slot_idx] == nullptr) {
+    WasmCode* prior_code = code_table_[slot_idx];
+    prior_tier = GetExecutionTier(prior_code);
+    tier = GetExecutionTier(code.get());
+    bool code_upgrade = !prior_tier.has_value() || !tier.has_value() ||
+                        prior_tier.value() < tier.value();
+    if (code_upgrade) {
       code_table_[slot_idx] = code.get();
     }
 
-    // Patch jump table.
-    JumpTableAssembler::PatchJumpTableSlot(jump_table_->instruction_start(),
-                                           slot_idx, code->instruction_start(),
-                                           WasmCode::kFlushICache);
+    // Patch jump table. Ensure to use optimized code and interpreter entries.
+    if (code_upgrade || code->kind_ == WasmCode::Kind::kInterpreterEntry) {
+      JumpTableAssembler::PatchJumpTableSlot(
+          jump_table_->instruction_start(), slot_idx, code->instruction_start(),
+          WasmCode::kFlushICache);
+    }
   }
   if (code->kind_ == WasmCode::Kind::kInterpreterEntry) {
     SetInterpreterRedirection(code->index());
   }
-  WasmCode* ret = code.get();
+  WasmCodeUpdate update;
+  update.code = code.get();
+  update.tier = tier;
+  update.prior_tier = prior_tier;
   owned_code_.emplace_back(std::move(code));
-  return ret;
+  return update;
 }
 
 WasmCode* NativeModule::AddDeserializedCode(
@@ -726,7 +791,7 @@ WasmCode* NativeModule::AddDeserializedCode(
   // Note: we do not flush the i-cache here, since the code needs to be
   // relocated anyway. The caller is responsible for flushing the i-cache later.
 
-  return PublishCode(std::move(code));
+  return PublishCode(std::move(code)).code;
 }
 
 std::vector<WasmCode*> NativeModule::SnapshotCodeTable() const {
@@ -758,7 +823,7 @@ WasmCode* NativeModule::CreateEmptyJumpTable(uint32_t jump_table_size) {
       OwnedVector<const uint8_t>{},             // source_pos
       WasmCode::kJumpTable,                     // kind
       WasmCode::kOther}};                       // tier
-  return PublishCode(std::move(code));
+  return PublishCode(std::move(code)).code;
 }
 
 Vector<byte> NativeModule::AllocateForCode(size_t size) {
@@ -1202,34 +1267,11 @@ void NativeModule::SampleCodeSize(
   histogram->AddSample(code_size_mb);
 }
 
-namespace {
-WasmCode::Tier GetCodeTierForExecutionTier(ExecutionTier tier) {
-  switch (tier) {
-    case ExecutionTier::kInterpreter:
-      return WasmCode::Tier::kOther;
-    case ExecutionTier::kBaseline:
-      return WasmCode::Tier::kLiftoff;
-    case ExecutionTier::kOptimized:
-      return WasmCode::Tier::kTurbofan;
-  }
-}
-
-WasmCode::Kind GetCodeKindForExecutionTier(ExecutionTier tier) {
-  switch (tier) {
-    case ExecutionTier::kInterpreter:
-      return WasmCode::Kind::kInterpreterEntry;
-    case ExecutionTier::kBaseline:
-    case ExecutionTier::kOptimized:
-      return WasmCode::Kind::kFunction;
-  }
-}
-}  // namespace
-
-WasmCode* NativeModule::AddCompiledCode(WasmCompilationResult result) {
+WasmCodeUpdate NativeModule::AddCompiledCode(WasmCompilationResult result) {
   return AddCompiledCode({&result, 1})[0];
 }
 
-std::vector<WasmCode*> NativeModule::AddCompiledCode(
+std::vector<WasmCodeUpdate> NativeModule::AddCompiledCode(
     Vector<WasmCompilationResult> results) {
   DCHECK(!results.is_empty());
   // First, allocate code space for all the results.
@@ -1259,16 +1301,15 @@ std::vector<WasmCode*> NativeModule::AddCompiledCode(
   DCHECK_EQ(0, code_space.size());
 
   // Under the {allocation_mutex_}, publish the code.
-  std::vector<WasmCode*> returned_code;
-  returned_code.reserve(results.size());
+  std::vector<WasmCodeUpdate> code_updates;
+  code_updates.reserve(results.size());
   {
     base::MutexGuard lock(&allocation_mutex_);
-    for (auto& result : generated_code) {
-      returned_code.push_back(PublishCodeLocked(std::move(result)));
-    }
+    for (auto& result : generated_code)
+      code_updates.push_back(PublishCodeLocked(std::move(result)));
   }
 
-  return returned_code;
+  return code_updates;
 }
 
 void NativeModule::FreeCode(Vector<WasmCode* const> codes) {

src/wasm/wasm-code-manager.h

@@ -14,6 +14,7 @@
 #include <vector>
 
 #include "src/base/macros.h"
+#include "src/base/optional.h"
 #include "src/builtins/builtins-definitions.h"
 #include "src/handles.h"
 #include "src/trap-handler/trap-handler.h"
@@ -72,6 +73,12 @@ class V8_EXPORT_PRIVATE DisjointAllocationPool final {
   DISALLOW_COPY_AND_ASSIGN(DisjointAllocationPool);
 };
 
+struct WasmCodeUpdate {
+  WasmCode* code = nullptr;
+  base::Optional<ExecutionTier> tier;
+  base::Optional<ExecutionTier> prior_tier;
+};
+
 class V8_EXPORT_PRIVATE WasmCode final {
  public:
   enum Kind {
@@ -270,9 +277,9 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // {PublishCode} makes the code available to the system by entering it into
   // the code table and patching the jump table. It returns a raw pointer to the
   // given {WasmCode} object.
-  WasmCode* PublishCode(std::unique_ptr<WasmCode>);
+  WasmCodeUpdate PublishCode(std::unique_ptr<WasmCode>);
   // Hold the {allocation_mutex_} when calling {PublishCodeLocked}.
-  WasmCode* PublishCodeLocked(std::unique_ptr<WasmCode>);
+  WasmCodeUpdate PublishCodeLocked(std::unique_ptr<WasmCode>);
 
   WasmCode* AddDeserializedCode(
       uint32_t index, Vector<const byte> instructions, uint32_t stack_slots,
@@ -288,10 +295,12 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // Adds anonymous code for testing purposes.
   WasmCode* AddCodeForTesting(Handle<Code> code);
 
-  // Use this to start lazy compilation for the entire module. It will use the
-  // existing {WasmCode::kWasmCompileLazy} runtime stub and populate the jump
-  // table with trampolines to that runtime stub.
-  void SetLazyBuiltin();
+  // Use this to setup lazy compilation for the entire module ({UseLazyStubs})
+  // or for individual functions ({UseLazyStub}). It will use the existing
+  // {WasmCode::kWasmCompileLazy} runtime stub and populate the jump table with
+  // trampolines to that runtime stub.
+  void UseLazyStubs();
+  void UseLazyStub(uint32_t func_index);
 
   // Initializes all runtime stubs by setting up entry addresses in the runtime
   // stub table. It must be called exactly once per native module before adding
@@ -370,6 +379,8 @@ class V8_EXPORT_PRIVATE NativeModule final {
   UseTrapHandler use_trap_handler() const { return use_trap_handler_; }
   void set_lazy_compile_frozen(bool frozen) { lazy_compile_frozen_ = frozen; }
   bool lazy_compile_frozen() const { return lazy_compile_frozen_; }
+  void set_lazy_compilation(bool lazy) { lazy_compilation_ = lazy; }
+  bool lazy_compilation() const { return lazy_compilation_; }
   Vector<const uint8_t> wire_bytes() const { return wire_bytes_->as_vector(); }
   const WasmModule* module() const { return module_.get(); }
   std::shared_ptr<const WasmModule> shared_module() const { return module_; }
@@ -394,8 +405,8 @@ class V8_EXPORT_PRIVATE NativeModule final {
   enum CodeSamplingTime : int8_t { kAfterBaseline, kAfterTopTier, kSampling };
   void SampleCodeSize(Counters*, CodeSamplingTime) const;
 
-  WasmCode* AddCompiledCode(WasmCompilationResult);
-  std::vector<WasmCode*> AddCompiledCode(Vector<WasmCompilationResult>);
+  WasmCodeUpdate AddCompiledCode(WasmCompilationResult);
+  std::vector<WasmCodeUpdate> AddCompiledCode(Vector<WasmCompilationResult>);
 
   // Free a set of functions of this module. Uncommits whole pages if possible.
   // The given vector must be ordered by the instruction start address, and all
@@ -524,6 +535,7 @@ class V8_EXPORT_PRIVATE NativeModule final {
   UseTrapHandler use_trap_handler_ = kNoTrapHandler;
   bool is_executable_ = false;
   bool lazy_compile_frozen_ = false;
+  bool lazy_compilation_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(NativeModule);
 };

src/wasm/wasm-module.h

@@ -195,6 +195,7 @@ struct V8_EXPORT_PRIVATE WasmModule {
   uint32_t num_declared_functions = 0;  // excluding imported
   uint32_t num_exported_functions = 0;
   uint32_t num_declared_data_segments = 0;  // From the DataCount section.
+  uint32_t num_lazy_compilation_hints = 0;  // From compilation hints section.
   WireBytesRef name = {0, 0};
   std::vector<FunctionSig*> signatures;  // by signature index
   std::vector<uint32_t> signature_ids;   // by signature index

src/wasm/wasm-serialization.cc

@@ -503,7 +503,12 @@ bool NativeModuleDeserializer::ReadHeader(Reader* reader) {
 
 bool NativeModuleDeserializer::ReadCode(uint32_t fn_index, Reader* reader) {
   size_t code_section_size = reader->Read<size_t>();
-  if (code_section_size == 0) return true;
+  if (code_section_size == 0) {
+    DCHECK(FLAG_wasm_lazy_compilation ||
+           native_module_->enabled_features().compilation_hints);
+    native_module_->UseLazyStub(fn_index);
+    return true;
+  }
   size_t constant_pool_offset = reader->Read<size_t>();
   size_t safepoint_table_offset = reader->Read<size_t>();
   size_t handler_table_offset = reader->Read<size_t>();
@@ -625,9 +630,8 @@ MaybeHandle<WasmModuleObject> DeserializeNativeModule(
       std::move(wire_bytes_copy), script, Handle<ByteArray>::null());
   NativeModule* native_module = module_object->native_module();
 
-  if (FLAG_wasm_lazy_compilation) {
-    native_module->SetLazyBuiltin();
-  }
+  native_module->set_lazy_compilation(FLAG_wasm_lazy_compilation);
+
   NativeModuleDeserializer deserializer(native_module);
 
   Reader reader(data + kVersionSize);

test/cctest/wasm/wasm-run-utils.cc

@@ -501,7 +501,9 @@ void WasmFunctionCompiler::Build(const byte* start, const byte* end) {
   WasmCompilationResult result = unit.ExecuteCompilation(
       &env, native_module->compilation_state()->GetWireBytesStorage(),
       isolate()->counters(), &unused_detected_features);
-  WasmCode* code = native_module->AddCompiledCode(std::move(result));
+  WasmCodeUpdate code_update =
+      native_module->AddCompiledCode(std::move(result));
+  WasmCode* code = code_update.code;
   DCHECK_NOT_NULL(code);
   if (WasmCode::ShouldBeLogged(isolate())) code->LogCode(isolate());
 }

test/unittests/wasm/wasm-code-manager-unittest.cc

@@ -177,7 +177,7 @@ class WasmCodeManagerTest : public TestWithContext,
     desc.instr_size = static_cast<int>(size);
     std::unique_ptr<WasmCode> code = native_module->AddCode(
         index, desc, 0, 0, {}, {}, WasmCode::kFunction, WasmCode::kOther);
-    return native_module->PublishCode(std::move(code));
+    return native_module->PublishCode(std::move(code)).code;
   }
 
   size_t page() const { return AllocatePageSize(); }