[wasm] Tear apart the WasmCompilationUnit

This refactoring is a big step towards separating Turbofan-related code
from backend independent code. This will allow us to include way less
headers from "src/compiler" at various places.

The {WasmCompilationUnit} contained information for Turbofan
compilation, and for Liftoff compilation. This CL tears this apart, such
that {WasmCompilationUnit} holds backend-independent information, plus
a pointer to either {LiftoffCompilationUnit} or
{TurbofanWasmCompilationUnit}. These pointers are opaque, so that
{function-compiler.h}, defining {WasmCompilationUnit}, does not need to
include any Turbofan specific or Liftoff specific headers.

R=ahaas@chromium.org, titzer@chromium.org, mstarzinger@chromium.org

Bug: v8:7570, v8:6600
Change-Id: I024c9a23508ee1b4b3cbe1d068c8e785d732daca
Reviewed-on: https://chromium-review.googlesource.com/1016640
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52684}

BUILD.gn

@@ -2304,6 +2304,7 @@ v8_source_set("v8_base") {
     "src/wasm/baseline/liftoff-assembler.cc",
     "src/wasm/baseline/liftoff-assembler.h",
     "src/wasm/baseline/liftoff-compiler.cc",
+    "src/wasm/baseline/liftoff-compiler.h",
     "src/wasm/baseline/liftoff-register.h",
     "src/wasm/compilation-manager.cc",
     "src/wasm/compilation-manager.h",
@@ -2311,6 +2312,8 @@ v8_source_set("v8_base") {
     "src/wasm/function-body-decoder-impl.h",
     "src/wasm/function-body-decoder.cc",
     "src/wasm/function-body-decoder.h",
+    "src/wasm/function-compiler.cc",
+    "src/wasm/function-compiler.h",
     "src/wasm/leb-helper.h",
     "src/wasm/local-decl-encoder.cc",
     "src/wasm/local-decl-encoder.h",

src/compiler/wasm-compiler.h

@@ -12,8 +12,8 @@
 #include "src/compiler.h"
 #include "src/optimized-compilation-info.h"
 #include "src/trap-handler/trap-handler.h"
-#include "src/wasm/baseline/liftoff-assembler.h"
 #include "src/wasm/function-body-decoder.h"
+#include "src/wasm/function-compiler.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
@@ -43,31 +43,12 @@ class WasmCode;
 
 namespace compiler {
 
-// The {ModuleEnv} encapsulates the module data that is used by the
-// {WasmGraphBuilder} during graph building.
-// ModuleEnvs are shareable across multiple compilations.
-struct ModuleEnv {
-  // A pointer to the decoded module's static representation.
-  const wasm::WasmModule* module;
-
-  // True if trap handling should be used in compiled code, rather than
-  // compiling in bounds checks for each memory access.
-  const bool use_trap_handler;
-
-  ModuleEnv(const wasm::WasmModule* module, bool use_trap_handler)
-      : module(module), use_trap_handler(use_trap_handler) {}
-};
-
-enum RuntimeExceptionSupport : bool {
-  kRuntimeExceptionSupport = true,
-  kNoRuntimeExceptionSupport = false
-};
-
 // Information about Wasm compilation that needs to be plumbed through the
 // different layers of the compiler.
 class WasmCompilationData {
  public:
-  explicit WasmCompilationData(RuntimeExceptionSupport);
+  explicit WasmCompilationData(
+      wasm::RuntimeExceptionSupport runtime_exception_support);
 
   void AddProtectedInstruction(uint32_t instr_offset, uint32_t landing_offset);
 
@@ -76,7 +57,7 @@ class WasmCompilationData {
     return std::move(protected_instructions_);
   }
 
-  RuntimeExceptionSupport runtime_exception_support() const {
+  wasm::RuntimeExceptionSupport runtime_exception_support() const {
     return runtime_exception_support_;
   }
 
@@ -84,115 +65,56 @@ class WasmCompilationData {
   std::unique_ptr<std::vector<trap_handler::ProtectedInstructionData>>
       protected_instructions_;
 
-  // See WasmGraphBuilder::runtime_exception_support_.
-  const RuntimeExceptionSupport runtime_exception_support_;
+  // See ModuleEnv::runtime_exception_support_.
+  wasm::RuntimeExceptionSupport runtime_exception_support_;
 
   DISALLOW_COPY_AND_ASSIGN(WasmCompilationData);
 };
 
-class WasmCompilationUnit final {
+class TurbofanWasmCompilationUnit {
  public:
-  enum class CompilationMode : uint8_t { kLiftoff, kTurbofan };
-  static CompilationMode GetDefaultCompilationMode();
-
-  // If constructing from a background thread, pass in a Counters*, and ensure
-  // that the Counters live at least as long as this compilation unit (which
-  // typically means to hold a std::shared_ptr<Counters>).
-  // If no such pointer is passed, Isolate::counters() will be called. This is
-  // only allowed to happen on the foreground thread.
-  WasmCompilationUnit(Isolate*, ModuleEnv*, wasm::NativeModule*,
-                      wasm::FunctionBody, wasm::WasmName, int index,
-                      Handle<Code> centry_stub,
-                      CompilationMode = GetDefaultCompilationMode(),
-                      Counters* = nullptr,
-                      RuntimeExceptionSupport = kRuntimeExceptionSupport,
-                      bool lower_simd = false);
-
-  ~WasmCompilationUnit();
+  explicit TurbofanWasmCompilationUnit(wasm::WasmCompilationUnit* wasm_unit)
+      : wasm_unit_(wasm_unit),
+        wasm_compilation_data_(wasm_unit->env_->runtime_exception_support) {}
 
-  void ExecuteCompilation();
-  wasm::WasmCode* FinishCompilation(wasm::ErrorThrower* thrower);
+  SourcePositionTable* BuildGraphForWasmFunction(double* decode_ms);
 
-  static wasm::WasmCode* CompileWasmFunction(
-      wasm::NativeModule* native_module, wasm::ErrorThrower* thrower,
-      Isolate* isolate, const wasm::ModuleWireBytes& wire_bytes, ModuleEnv* env,
-      const wasm::WasmFunction* function,
-      CompilationMode = GetDefaultCompilationMode());
+  void ExecuteCompilation();
 
-  size_t memory_cost() const { return memory_cost_; }
-  wasm::NativeModule* native_module() const { return native_module_; }
+  wasm::WasmCode* FinishCompilation(wasm::ErrorThrower*);
 
  private:
-  struct LiftoffData {
-    wasm::LiftoffAssembler asm_;
-    int safepoint_table_offset_;
-    SourcePositionTableBuilder source_position_table_builder_;
-    // The {codegen_zone_} needs to survive until FinishCompilation. It's only
-    // rarely used (e.g. for runtime calls), so it's only allocated when needed.
-    std::unique_ptr<Zone> codegen_zone_;
-    explicit LiftoffData(Isolate* isolate) : asm_(isolate) {}
-  };
-  struct TurbofanData {
-    // The graph zone is deallocated at the end of ExecuteCompilation by virtue
-    // of it being zone allocated.
-    JSGraph* jsgraph_ = nullptr;
-    // The compilation_zone_, info_, and job_ fields need to survive past
-    // ExecuteCompilation, onto FinishCompilation (which happens on the main
-    // thread).
-    std::unique_ptr<Zone> compilation_zone_;
-    std::unique_ptr<OptimizedCompilationInfo> info_;
-    std::unique_ptr<OptimizedCompilationJob> job_;
-    wasm::Result<wasm::DecodeStruct*> graph_construction_result_;
-  };
-
-  // Turbofan.
-  SourcePositionTable* BuildGraphForWasmFunction(double* decode_ms);
-  void ExecuteTurbofanCompilation();
-  wasm::WasmCode* FinishTurbofanCompilation(wasm::ErrorThrower*);
-
-  // Liftoff.
-  bool ExecuteLiftoffCompilation();
-  wasm::WasmCode* FinishLiftoffCompilation(wasm::ErrorThrower*);
-
-  Isolate* isolate_;
-  ModuleEnv* env_;
-  wasm::FunctionBody func_body_;
-  wasm::WasmName func_name_;
-  Counters* counters_;
-  Handle<Code> centry_stub_;
-  int func_index_;
-  bool ok_ = true;
-  size_t memory_cost_ = 0;
-  wasm::NativeModule* native_module_;
-  bool lower_simd_;
+  wasm::WasmCompilationUnit* const wasm_unit_;
   WasmCompilationData wasm_compilation_data_;
-  CompilationMode mode_;
-  // {liftoff_} is valid if mode_ == kLiftoff, tf_ if mode_ == kTurbofan.
-  union {
-    LiftoffData liftoff_;
-    TurbofanData tf_;
-  };
-
-  Counters* counters() { return counters_; }
-
-  DISALLOW_COPY_AND_ASSIGN(WasmCompilationUnit);
+  bool ok_ = true;
+  // The graph zone is deallocated at the end of {ExecuteCompilation} by virtue
+  // of it being zone allocated.
+  JSGraph* jsgraph_ = nullptr;
+  // The compilation_zone_, info_, and job_ fields need to survive past
+  // {ExecuteCompilation}, onto {FinishCompilation} (which happens on the main
+  // thread).
+  std::unique_ptr<Zone> compilation_zone_;
+  std::unique_ptr<OptimizedCompilationInfo> info_;
+  std::unique_ptr<OptimizedCompilationJob> job_;
+  wasm::Result<wasm::DecodeStruct*> graph_construction_result_;
+
+  DISALLOW_COPY_AND_ASSIGN(TurbofanWasmCompilationUnit);
 };
 
 // Wraps a JS function, producing a code object that can be called from wasm.
-Handle<Code> CompileWasmToJSWrapper(Isolate* isolate, Handle<JSReceiver> target,
-                                    wasm::FunctionSig* sig, uint32_t index,
-                                    wasm::ModuleOrigin origin,
-                                    bool use_trap_handler);
+Handle<Code> CompileWasmToJSWrapper(Isolate*, Handle<JSReceiver> target,
+                                    wasm::FunctionSig*, uint32_t index,
+                                    wasm::ModuleOrigin, wasm::UseTrapHandler);
 
 // Wraps a given wasm code object, producing a code object.
 V8_EXPORT_PRIVATE Handle<Code> CompileJSToWasmWrapper(
-    Isolate* isolate, wasm::WasmModule* module, Handle<WeakCell> weak_instance,
-    wasm::WasmCode* wasm_code, uint32_t index, bool use_trap_handler);
+    Isolate*, wasm::WasmModule*, Handle<WeakCell> weak_instance,
+    wasm::WasmCode*, uint32_t index, wasm::UseTrapHandler);
 
 // Compiles a stub that redirects a call to a wasm function to the wasm
 // interpreter. It's ABI compatible with the compiled wasm function.
-Handle<Code> CompileWasmInterpreterEntry(Isolate* isolate, uint32_t func_index,
-                                         wasm::FunctionSig* sig);
+Handle<Code> CompileWasmInterpreterEntry(Isolate*, uint32_t func_index,
+                                         wasm::FunctionSig*);
 
 // Helper function to get the offset into a fixed array for a given {index}.
 // TODO(titzer): access-builder.h is not accessible outside compiler. Move?
@@ -228,11 +150,10 @@ class WasmGraphBuilder {
  public:
   enum EnforceBoundsCheck : bool { kNeedsBoundsCheck, kCanOmitBoundsCheck };
 
-  WasmGraphBuilder(ModuleEnv* env, Zone* zone, JSGraph* graph,
+  WasmGraphBuilder(wasm::ModuleEnv* env, Zone* zone, JSGraph* graph,
                    Handle<Code> centry_stub, Handle<Oddball> anyref_null,
                    wasm::FunctionSig* sig,
-                   compiler::SourcePositionTable* spt = nullptr,
-                   RuntimeExceptionSupport res = kRuntimeExceptionSupport);
+                   compiler::SourcePositionTable* spt = nullptr);
 
   Node** Buffer(size_t count) {
     if (count > cur_bufsize_) {
@@ -423,7 +344,7 @@ class WasmGraphBuilder {
   Node* const anyref_null_node_;
   // env_ == nullptr means we're not compiling Wasm functions, such as for
   // wrappers or interpreter stubs.
-  ModuleEnv* const env_ = nullptr;
+  wasm::ModuleEnv* const env_ = nullptr;
   SetOncePointer<Node> instance_node_;
   struct FunctionTableNodes {
     Node* table_addr;
@@ -439,10 +360,6 @@ class WasmGraphBuilder {
   bool has_simd_ = false;
   bool needs_stack_check_ = false;
   const bool untrusted_code_mitigations_ = true;
-  // If the runtime doesn't support exception propagation,
-  // we won't generate stack checks, and trap handling will also
-  // be generated differently.
-  const RuntimeExceptionSupport runtime_exception_support_;
 
   wasm::FunctionSig* const sig_;
   SetOncePointer<const Operator> allocate_heap_number_operator_;

src/wasm/baseline/liftoff-compiler.cc

@@ -2,15 +2,18 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "src/wasm/baseline/liftoff-assembler.h"
+#include "src/wasm/baseline/liftoff-compiler.h"
 
 #include "src/assembler-inl.h"
 #include "src/base/optional.h"
+// TODO(clemensh): Remove dependences on compiler stuff.
 #include "src/compiler/linkage.h"
 #include "src/compiler/wasm-compiler.h"
 #include "src/counters.h"
 #include "src/macro-assembler-inl.h"
+#include "src/wasm/baseline/liftoff-assembler.h"
 #include "src/wasm/function-body-decoder-impl.h"
+#include "src/wasm/function-compiler.h"
 #include "src/wasm/memory-tracing.h"
 #include "src/wasm/wasm-objects.h"
 #include "src/wasm/wasm-opcodes.h"
@@ -19,8 +22,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-using WasmCompilationData = compiler::WasmCompilationData;
-
 constexpr auto kRegister = LiftoffAssembler::VarState::kRegister;
 constexpr auto KIntConst = LiftoffAssembler::VarState::KIntConst;
 constexpr auto kStack = LiftoffAssembler::VarState::kStack;
@@ -122,10 +123,10 @@ class LiftoffCompiler {
   };
 
   LiftoffCompiler(LiftoffAssembler* liftoff_asm,
-                  compiler::CallDescriptor* call_descriptor,
-                  compiler::ModuleEnv* env,
+                  compiler::CallDescriptor* call_descriptor, ModuleEnv* env,
                   SourcePositionTableBuilder* source_position_table_builder,
-                  WasmCompilationData* wasm_compilation_data,
+                  std::vector<trap_handler::ProtectedInstructionData>*
+                      protected_instructions,
                   Zone* compilation_zone, std::unique_ptr<Zone>* codegen_zone,
                   WasmCode* const* code_table_entry)
       : asm_(liftoff_asm),
@@ -138,7 +139,7 @@ class LiftoffCompiler {
                                : wasm::kV8MaxWasmMemoryPages} *
                   wasm::kWasmPageSize),
         source_position_table_builder_(source_position_table_builder),
-        wasm_compilation_data_(wasm_compilation_data),
+        protected_instructions_(protected_instructions),
         compilation_zone_(compilation_zone),
         codegen_zone_(codegen_zone),
         safepoint_table_builder_(compilation_zone_),
@@ -280,10 +281,7 @@ class LiftoffCompiler {
   }
 
   void StackCheck(wasm::WasmCodePosition position) {
-    if (FLAG_wasm_no_stack_checks ||
-        !wasm_compilation_data_->runtime_exception_support()) {
-      return;
-    }
+    if (FLAG_wasm_no_stack_checks || !env_->runtime_exception_support) return;
     out_of_line_code_.push_back(
         OutOfLineCode::StackCheck(position, __ cache_state()->used_registers));
     OutOfLineCode& ool = out_of_line_code_.back();
@@ -444,10 +442,11 @@ class LiftoffCompiler {
     if (is_mem_out_of_bounds && env_->use_trap_handler) {
       uint32_t pc = static_cast<uint32_t>(__ pc_offset());
       DCHECK_EQ(pc, __ pc_offset());
-      wasm_compilation_data_->AddProtectedInstruction(ool.pc, pc);
+      protected_instructions_->emplace_back(
+          trap_handler::ProtectedInstructionData{ool.pc, pc});
     }
 
-    if (!wasm_compilation_data_->runtime_exception_support()) {
+    if (!env_->runtime_exception_support) {
       // We cannot test calls to the runtime in cctest/test-run-wasm.
       // Therefore we emit a call to C here instead of a call to the runtime.
       // In this mode, we never generate stack checks.
@@ -1610,14 +1609,14 @@ class LiftoffCompiler {
  private:
   LiftoffAssembler* const asm_;
   compiler::CallDescriptor* const descriptor_;
-  compiler::ModuleEnv* const env_;
+  ModuleEnv* const env_;
   // {min_size_} and {max_size_} are cached values computed from the ModuleEnv.
   const uint64_t min_size_;
   const uint64_t max_size_;
   bool ok_ = true;
   std::vector<OutOfLineCode> out_of_line_code_;
   SourcePositionTableBuilder* const source_position_table_builder_;
-  WasmCompilationData* wasm_compilation_data_;
+  std::vector<trap_handler::ProtectedInstructionData>* protected_instructions_;
   // Zone used to store information during compilation. The result will be
   // stored independently, such that this zone can die together with the
   // LiftoffCompiler after compilation.
@@ -1657,30 +1656,37 @@ class LiftoffCompiler {
 };
 
 }  // namespace
-}  // namespace wasm
 
-bool compiler::WasmCompilationUnit::ExecuteLiftoffCompilation() {
+bool LiftoffCompilationUnit::ExecuteCompilation() {
   base::ElapsedTimer compile_timer;
   if (FLAG_trace_wasm_decode_time) {
     compile_timer.Start();
   }
 
-  Zone zone(isolate_->allocator(), "LiftoffCompilationZone");
-  const wasm::WasmModule* module = env_ ? env_->module : nullptr;
-  auto call_descriptor = compiler::GetWasmCallDescriptor(&zone, func_body_.sig);
+  Zone zone(wasm_unit_->isolate_->allocator(), "LiftoffCompilationZone");
+  const wasm::WasmModule* module =
+      wasm_unit_->env_ ? wasm_unit_->env_->module : nullptr;
+  auto call_descriptor =
+      compiler::GetWasmCallDescriptor(&zone, wasm_unit_->func_body_.sig);
   base::Optional<TimedHistogramScope> liftoff_compile_time_scope(
-      base::in_place, counters()->liftoff_compile_time());
+      base::in_place, wasm_unit_->counters_->liftoff_compile_time());
   wasm::WasmCode* const* code_table_entry =
-      native_module_->code_table().data() + func_index_;
+      wasm_unit_->native_module_->code_table().data() + wasm_unit_->func_index_;
+  DCHECK(!protected_instructions_);
+  protected_instructions_.reset(
+      new std::vector<trap_handler::ProtectedInstructionData>());
   wasm::WasmFullDecoder<wasm::Decoder::kValidate, wasm::LiftoffCompiler>
-      decoder(&zone, module, func_body_, &liftoff_.asm_, call_descriptor, env_,
-              &liftoff_.source_position_table_builder_, &wasm_compilation_data_,
-              &zone, &liftoff_.codegen_zone_, code_table_entry);
+      decoder(&zone, module, wasm_unit_->func_body_, &asm_, call_descriptor,
+              wasm_unit_->env_, &source_position_table_builder_,
+              protected_instructions_.get(), &zone, &codegen_zone_,
+              code_table_entry);
   decoder.Decode();
   liftoff_compile_time_scope.reset();
   if (!decoder.interface().ok()) {
     // Liftoff compilation failed.
-    isolate_->counters()->liftoff_unsupported_functions()->Increment();
+    wasm_unit_->isolate_->counters()
+        ->liftoff_unsupported_functions()
+        ->Increment();
     return false;
   }
   if (decoder.failed()) return false;  // Validation error
@@ -1690,22 +1696,46 @@ bool compiler::WasmCompilationUnit::ExecuteLiftoffCompilation() {
     PrintF(
         "wasm-compilation liftoff phase 1 ok: %u bytes, %0.3f ms decode and "
         "compile\n",
-        static_cast<unsigned>(func_body_.end - func_body_.start), compile_ms);
+        static_cast<unsigned>(wasm_unit_->func_body_.end -
+                              wasm_unit_->func_body_.start),
+        compile_ms);
   }
 
   // Record the memory cost this unit places on the system until
   // it is finalized.
-  memory_cost_ = liftoff_.asm_.pc_offset();
-  liftoff_.safepoint_table_offset_ =
-      decoder.interface().GetSafepointTableOffset();
-  isolate_->counters()->liftoff_compiled_functions()->Increment();
+  wasm_unit_->memory_cost_ =
+      asm_.pc_offset() +
+      protected_instructions_->size() *
+          sizeof(trap_handler::ProtectedInstructionData) +
+      (codegen_zone_ ? codegen_zone_->allocation_size() : 0);
+
+  safepoint_table_offset_ = decoder.interface().GetSafepointTableOffset();
+  wasm_unit_->isolate_->counters()->liftoff_compiled_functions()->Increment();
   return true;
 }
 
+wasm::WasmCode* LiftoffCompilationUnit::FinishCompilation(
+    wasm::ErrorThrower* thrower) {
+  CodeDesc desc;
+  asm_.GetCode(wasm_unit_->isolate_, &desc);
+
+  Handle<ByteArray> source_positions =
+      source_position_table_builder_.ToSourcePositionTable(
+          wasm_unit_->isolate_);
+
+  wasm::WasmCode* code = wasm_unit_->native_module_->AddCode(
+      desc, asm_.GetTotalFrameSlotCount(), wasm_unit_->func_index_,
+      safepoint_table_offset_, 0, std::move(protected_instructions_),
+      source_positions, wasm::WasmCode::kLiftoff);
+
+  return code;
+}
+
 #undef __
 #undef TRACE
 #undef WASM_INSTANCE_OBJECT_OFFSET
 #undef LOAD_INSTANCE_FIELD
 
+}  // namespace wasm
 }  // namespace internal
 }  // namespace v8

src/wasm/baseline/liftoff-compiler.h

+// Copyright 2018 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.
+
+#ifndef V8_WASM_BASELINE_LIFTOFF_COMPILER_H_
+#define V8_WASM_BASELINE_LIFTOFF_COMPILER_H_
+
+#include "src/source-position-table.h"
+#include "src/trap-handler/trap-handler.h"
+#include "src/wasm/baseline/liftoff-assembler.h"
+#include "src/wasm/function-body-decoder.h"
+#include "src/wasm/function-compiler.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+class LiftoffCompilationUnit final {
+ public:
+  explicit LiftoffCompilationUnit(WasmCompilationUnit* wasm_unit)
+      : wasm_unit_(wasm_unit), asm_(wasm_unit->isolate_) {}
+
+  bool ExecuteCompilation();
+  wasm::WasmCode* FinishCompilation(wasm::ErrorThrower*);
+
+ private:
+  WasmCompilationUnit* const wasm_unit_;
+  wasm::LiftoffAssembler asm_;
+  int safepoint_table_offset_;
+  SourcePositionTableBuilder source_position_table_builder_;
+  std::unique_ptr<std::vector<trap_handler::ProtectedInstructionData>>
+      protected_instructions_;
+
+  // The {codegen_zone_} needs to survive until FinishCompilation. It's only
+  // rarely used (e.g. for runtime calls), so it's only allocated when needed.
+  std::unique_ptr<Zone> codegen_zone_;
+
+  DISALLOW_COPY_AND_ASSIGN(LiftoffCompilationUnit);
+};
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_WASM_BASELINE_LIFTOFF_COMPILER_H_

src/wasm/function-compiler.cc

+// Copyright 2018 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/wasm/function-compiler.h"
+
+#include "src/code-stubs.h"
+#include "src/compiler/wasm-compiler.h"
+#include "src/counters.h"
+#include "src/macro-assembler-inl.h"
+#include "src/wasm/baseline/liftoff-compiler.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+// static
+WasmCompilationUnit::CompilationMode
+WasmCompilationUnit::GetDefaultCompilationMode() {
+  return FLAG_liftoff ? CompilationMode::kLiftoff : CompilationMode::kTurbofan;
+}
+
+WasmCompilationUnit::WasmCompilationUnit(Isolate* isolate, ModuleEnv* env,
+                                         wasm::NativeModule* native_module,
+                                         wasm::FunctionBody body,
+                                         wasm::WasmName name, int index,
+                                         Handle<Code> centry_stub,
+                                         CompilationMode mode,
+                                         Counters* counters, bool lower_simd)
+    : isolate_(isolate),
+      env_(env),
+      func_body_(body),
+      func_name_(name),
+      counters_(counters ? counters : isolate->counters()),
+      centry_stub_(centry_stub),
+      func_index_(index),
+      native_module_(native_module),
+      lower_simd_(lower_simd),
+      mode_(mode) {
+  SwitchMode(mode);
+}
+
+// Declared here such that {LiftoffCompilationUnit} and
+// {TurbofanWasmCompilationUnit} can be opaque in the header file.
+WasmCompilationUnit::~WasmCompilationUnit() {}
+
+void WasmCompilationUnit::ExecuteCompilation() {
+  auto size_histogram = env_->module->is_wasm()
+                            ? counters_->wasm_wasm_function_size_bytes()
+                            : counters_->wasm_asm_function_size_bytes();
+  size_histogram->AddSample(
+      static_cast<int>(func_body_.end - func_body_.start));
+  auto timed_histogram = env_->module->is_wasm()
+                             ? counters_->wasm_compile_wasm_function_time()
+                             : counters_->wasm_compile_asm_function_time();
+  TimedHistogramScope wasm_compile_function_time_scope(timed_histogram);
+
+  if (FLAG_trace_wasm_compiler) {
+    PrintF("Compiling wasm function %d\n\n", func_index_);
+  }
+
+  switch (mode_) {
+    case WasmCompilationUnit::CompilationMode::kLiftoff:
+      if (liftoff_unit_->ExecuteCompilation()) break;
+      // Otherwise, fall back to turbofan.
+      SwitchMode(CompilationMode::kTurbofan);
+      V8_FALLTHROUGH;
+    case WasmCompilationUnit::CompilationMode::kTurbofan:
+      turbofan_unit_->ExecuteCompilation();
+      break;
+  }
+}
+
+wasm::WasmCode* WasmCompilationUnit::FinishCompilation(
+    wasm::ErrorThrower* thrower) {
+  wasm::WasmCode* ret;
+  switch (mode_) {
+    case CompilationMode::kLiftoff:
+      ret = liftoff_unit_->FinishCompilation(thrower);
+      break;
+    case CompilationMode::kTurbofan:
+      ret = turbofan_unit_->FinishCompilation(thrower);
+      break;
+    default:
+      UNREACHABLE();
+  }
+  if (ret == nullptr) {
+    thrower->RuntimeError("Error finalizing code.");
+  }
+  return ret;
+}
+
+void WasmCompilationUnit::SwitchMode(CompilationMode new_mode) {
+  // This method is being called in the constructor, where neither
+  // {liftoff_unit_} nor {turbofan_unit_} are set, or to switch mode from
+  // kLiftoff to kTurbofan, in which case {liftoff_unit_} is already set.
+  mode_ = new_mode;
+  switch (new_mode) {
+    case CompilationMode::kLiftoff:
+      DCHECK(!turbofan_unit_);
+      DCHECK(!liftoff_unit_);
+      liftoff_unit_.reset(new LiftoffCompilationUnit(this));
+      return;
+    case CompilationMode::kTurbofan:
+      DCHECK(!turbofan_unit_);
+      liftoff_unit_.reset();
+      turbofan_unit_.reset(new compiler::TurbofanWasmCompilationUnit(this));
+      return;
+  }
+  UNREACHABLE();
+}
+
+// static
+wasm::WasmCode* WasmCompilationUnit::CompileWasmFunction(
+    wasm::NativeModule* native_module, wasm::ErrorThrower* thrower,
+    Isolate* isolate, const wasm::ModuleWireBytes& wire_bytes, ModuleEnv* env,
+    const wasm::WasmFunction* function, CompilationMode mode) {
+  wasm::FunctionBody function_body{
+      function->sig, function->code.offset(),
+      wire_bytes.start() + function->code.offset(),
+      wire_bytes.start() + function->code.end_offset()};
+
+  WasmCompilationUnit unit(isolate, env, native_module, function_body,
+                           wire_bytes.GetNameOrNull(function, env->module),
+                           function->func_index,
+                           CEntryStub(isolate, 1).GetCode(), mode);
+  unit.ExecuteCompilation();
+  return unit.FinishCompilation(thrower);
+}
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8

src/wasm/function-compiler.h

+// Copyright 2018 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.
+
+#ifndef V8_WASM_FUNCTION_COMPILER_H_
+#define V8_WASM_FUNCTION_COMPILER_H_
+
+#include "src/wasm/function-body-decoder.h"
+
+namespace v8 {
+namespace internal {
+
+namespace compiler {
+class TurbofanWasmCompilationUnit;
+}  // namespace compiler
+
+namespace wasm {
+
+class LiftoffCompilationUnit;
+struct ModuleWireBytes;
+class NativeModule;
+class WasmCode;
+struct WasmFunction;
+
+enum RuntimeExceptionSupport : bool {
+  kRuntimeExceptionSupport = true,
+  kNoRuntimeExceptionSupport = false
+};
+
+enum UseTrapHandler : bool { kUseTrapHandler = true, kNoTrapHandler = false };
+
+// The {ModuleEnv} encapsulates the module data that is used during compilation.
+// ModuleEnvs are shareable across multiple compilations.
+struct ModuleEnv {
+  // A pointer to the decoded module's static representation.
+  const WasmModule* const module;
+
+  // True if trap handling should be used in compiled code, rather than
+  // compiling in bounds checks for each memory access.
+  const UseTrapHandler use_trap_handler;
+
+  // If the runtime doesn't support exception propagation,
+  // we won't generate stack checks, and trap handling will also
+  // be generated differently.
+  const RuntimeExceptionSupport runtime_exception_support;
+
+  constexpr ModuleEnv(const WasmModule* module, UseTrapHandler use_trap_handler,
+                      RuntimeExceptionSupport runtime_exception_support)
+      : module(module),
+        use_trap_handler(use_trap_handler),
+        runtime_exception_support(runtime_exception_support) {}
+};
+
+class WasmCompilationUnit final {
+ public:
+  enum class CompilationMode : uint8_t { kLiftoff, kTurbofan };
+  static CompilationMode GetDefaultCompilationMode();
+
+  // If constructing from a background thread, pass in a Counters*, and ensure
+  // that the Counters live at least as long as this compilation unit (which
+  // typically means to hold a std::shared_ptr<Counters>).
+  // If no such pointer is passed, Isolate::counters() will be called. This is
+  // only allowed to happen on the foreground thread.
+  WasmCompilationUnit(Isolate*, ModuleEnv*, wasm::NativeModule*,
+                      wasm::FunctionBody, wasm::WasmName, int index,
+                      Handle<Code> centry_stub,
+                      CompilationMode = GetDefaultCompilationMode(),
+                      Counters* = nullptr, bool lower_simd = false);
+
+  ~WasmCompilationUnit();
+
+  void ExecuteCompilation();
+  wasm::WasmCode* FinishCompilation(wasm::ErrorThrower* thrower);
+
+  static wasm::WasmCode* CompileWasmFunction(
+      wasm::NativeModule* native_module, wasm::ErrorThrower* thrower,
+      Isolate* isolate, const wasm::ModuleWireBytes& wire_bytes, ModuleEnv* env,
+      const wasm::WasmFunction* function,
+      CompilationMode = GetDefaultCompilationMode());
+
+  size_t memory_cost() const { return memory_cost_; }
+  wasm::NativeModule* native_module() const { return native_module_; }
+
+ private:
+  friend class LiftoffCompilationUnit;
+  friend class compiler::TurbofanWasmCompilationUnit;
+
+  Isolate* isolate_;
+  ModuleEnv* env_;
+  wasm::FunctionBody func_body_;
+  wasm::WasmName func_name_;
+  Counters* counters_;
+  Handle<Code> centry_stub_;
+  int func_index_;
+  size_t memory_cost_ = 0;
+  wasm::NativeModule* native_module_;
+  // TODO(wasm): Put {lower_simd_} inside the {ModuleEnv}.
+  bool lower_simd_;
+  CompilationMode mode_;
+  // LiftoffCompilationUnit, set if {mode_ == kLiftoff}.
+  std::unique_ptr<LiftoffCompilationUnit> liftoff_unit_;
+  // TurbofanWasmCompilationUnit, set if {mode_ == kTurbofan}.
+  std::unique_ptr<compiler::TurbofanWasmCompilationUnit> turbofan_unit_;
+
+  void SwitchMode(CompilationMode new_mode);
+
+  DISALLOW_COPY_AND_ASSIGN(WasmCompilationUnit);
+};
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_WASM_FUNCTION_COMPILER_H_

src/wasm/module-compiler.h

@@ -20,9 +20,10 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
+class CompilationState;
 class ModuleCompiler;
+struct ModuleEnv;
 class WasmCode;
-class CompilationState;
 
 struct CompilationStateDeleter {
   void operator()(CompilationState* compilation_state) const;
@@ -137,7 +138,7 @@ class AsyncCompileJob {
   ModuleWireBytes wire_bytes_;
   Handle<Context> context_;
   Handle<JSPromise> module_promise_;
-  std::unique_ptr<compiler::ModuleEnv> module_env_;
+  std::unique_ptr<ModuleEnv> module_env_;
   std::unique_ptr<WasmModule> module_;
 
   std::vector<DeferredHandles*> deferred_handles_;

src/wasm/module-decoder.h

@@ -13,12 +13,9 @@
 
 namespace v8 {
 namespace internal {
+namespace wasm {
 
-namespace compiler {
 struct ModuleEnv;
-}
-
-namespace wasm {
 
 inline bool IsValidSectionCode(uint8_t byte) {
   return kTypeSectionCode <= byte && byte <= kLastKnownModuleSection;
@@ -82,10 +79,9 @@ V8_EXPORT_PRIVATE FunctionResult SyncDecodeWasmFunction(
     const WasmModule* module, const byte* function_start,
     const byte* function_end);
 
-V8_EXPORT_PRIVATE FunctionResult
-AsyncDecodeWasmFunction(Isolate* isolate, Zone* zone, compiler::ModuleEnv* env,
-                        const byte* function_start, const byte* function_end,
-                        const std::shared_ptr<Counters> async_counters);
+V8_EXPORT_PRIVATE FunctionResult AsyncDecodeWasmFunction(
+    Isolate* isolate, Zone* zone, ModuleEnv* env, const byte* function_start,
+    const byte* function_end, const std::shared_ptr<Counters> async_counters);
 
 V8_EXPORT_PRIVATE WasmInitExpr DecodeWasmInitExprForTesting(const byte* start,
                                                             const byte* end);

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

@@ -1972,8 +1972,7 @@ static void TestBuildGraphForSimpleExpression(WasmOpcode opcode) {
     byte code[] = {WASM_NO_LOCALS, kExprGetLocal, 0, static_cast<byte>(opcode),
                    WASM_END};
     TestBuildingGraph(&zone, &jsgraph, nullptr, sig, nullptr, code,
-                      code + arraysize(code),
-                      compiler::kNoRuntimeExceptionSupport);
+                      code + arraysize(code));
   } else {
     CHECK_EQ(2, sig->parameter_count());
     byte code[] = {WASM_NO_LOCALS,
@@ -1984,8 +1983,7 @@ static void TestBuildGraphForSimpleExpression(WasmOpcode opcode) {
                    static_cast<byte>(opcode),
                    WASM_END};
     TestBuildingGraph(&zone, &jsgraph, nullptr, sig, nullptr, code,
-                      code + arraysize(code),
-                      compiler::kNoRuntimeExceptionSupport);
+                      code + arraysize(code));
   }
 }
 

test/cctest/wasm/test-wasm-stack.cc

@@ -158,8 +158,7 @@ WASM_EXEC_TEST(CollectDetailedWasmStack_WasmError) {
     int unreachable_pos = 1 << (8 * pos_shift);
     TestSignatures sigs;
     // Create a WasmRunner with stack checks and traps enabled.
-    WasmRunner<int> r(execution_mode, 0, "main",
-                      compiler::kRuntimeExceptionSupport);
+    WasmRunner<int> r(execution_mode, 0, "main", kRuntimeExceptionSupport);
 
     std::vector<byte> code(unreachable_pos + 1, kExprNop);
     code[unreachable_pos] = kExprUnreachable;

test/cctest/wasm/test-wasm-trap-position.cc

@@ -70,8 +70,7 @@ void CheckExceptionInfos(v8::internal::Isolate* i_isolate, Handle<Object> exc,
 // Trigger a trap for executing unreachable.
 WASM_EXEC_TEST(Unreachable) {
   // Create a WasmRunner with stack checks and traps enabled.
-  WasmRunner<void> r(execution_mode, 0, "main",
-                     compiler::kRuntimeExceptionSupport);
+  WasmRunner<void> r(execution_mode, 0, "main", kRuntimeExceptionSupport);
   TestSignatures sigs;
 
   BUILD(r, WASM_UNREACHABLE);
@@ -105,8 +104,7 @@ WASM_EXEC_TEST(Unreachable) {
 
 // Trigger a trap for loading from out-of-bounds.
 WASM_EXEC_TEST(IllegalLoad) {
-  WasmRunner<void> r(execution_mode, 0, "main",
-                     compiler::kRuntimeExceptionSupport);
+  WasmRunner<void> r(execution_mode, 0, "main", kRuntimeExceptionSupport);
   TestSignatures sigs;
 
   r.builder().AddMemory(0L);

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

@@ -15,7 +15,7 @@ namespace wasm {
 
 TestingModuleBuilder::TestingModuleBuilder(
     Zone* zone, ManuallyImportedJSFunction* maybe_import,
-    WasmExecutionMode mode, compiler::RuntimeExceptionSupport exception_support,
+    WasmExecutionMode mode, RuntimeExceptionSupport exception_support,
     LowerSimd lower_simd)
     : test_module_ptr_(&test_module_),
       isolate_(CcTest::InitIsolateOnce()),
@@ -45,7 +45,8 @@ TestingModuleBuilder::TestingModuleBuilder(
     Handle<Code> code = compiler::CompileWasmToJSWrapper(
         isolate_, maybe_import->js_function, maybe_import->sig,
         maybe_import_index, test_module_.origin(),
-        trap_handler::IsTrapHandlerEnabled());
+        trap_handler::IsTrapHandlerEnabled() ? kUseTrapHandler
+                                             : kNoTrapHandler);
     native_module_->ResizeCodeTableForTesting(maybe_import_index + 1,
                                               kMaxFunctions);
     auto wasm_to_js_wrapper = native_module_->AddCodeCopy(
@@ -126,7 +127,7 @@ Handle<JSFunction> TestingModuleBuilder::WrapCode(uint32_t index) {
                                  isolate_);
   Handle<Code> ret_code = compiler::CompileJSToWasmWrapper(
       isolate_, &test_module_, weak_instance, code, index,
-      trap_handler::IsTrapHandlerEnabled());
+      trap_handler::IsTrapHandlerEnabled() ? kUseTrapHandler : kNoTrapHandler);
   Handle<JSFunction> ret = WasmExportedFunction::New(
       isolate_, instance_object(), MaybeHandle<String>(),
       static_cast<int>(index),
@@ -192,8 +193,11 @@ uint32_t TestingModuleBuilder::AddBytes(Vector<const byte> bytes) {
   return bytes_offset;
 }
 
-compiler::ModuleEnv TestingModuleBuilder::CreateModuleEnv() {
-  return {&test_module_, trap_handler::IsTrapHandlerEnabled()};
+ModuleEnv TestingModuleBuilder::CreateModuleEnv() {
+  return {
+      &test_module_,
+      trap_handler::IsTrapHandlerEnabled() ? kUseTrapHandler : kNoTrapHandler,
+      runtime_exception_support_};
 }
 
 const WasmGlobal* TestingModuleBuilder::AddGlobal(ValueType type) {
@@ -263,22 +267,21 @@ void TestBuildingGraphWithBuilder(compiler::WasmGraphBuilder* builder,
   }
 }
 
-void TestBuildingGraph(
-    Zone* zone, compiler::JSGraph* jsgraph, compiler::ModuleEnv* module,
-    FunctionSig* sig, compiler::SourcePositionTable* source_position_table,
-    const byte* start, const byte* end,
-    compiler::RuntimeExceptionSupport runtime_exception_support) {
+void TestBuildingGraph(Zone* zone, compiler::JSGraph* jsgraph,
+                       ModuleEnv* module, FunctionSig* sig,
+                       compiler::SourcePositionTable* source_position_table,
+                       const byte* start, const byte* end) {
   if (module) {
     compiler::WasmGraphBuilder builder(
         module, zone, jsgraph, CEntryStub(jsgraph->isolate(), 1).GetCode(),
-        jsgraph->isolate()->factory()->null_value(), sig, source_position_table,
-        runtime_exception_support);
+        jsgraph->isolate()->factory()->null_value(), sig,
+        source_position_table);
     TestBuildingGraphWithBuilder(&builder, zone, sig, start, end);
   } else {
     compiler::WasmGraphBuilder builder(
         nullptr, zone, jsgraph, CEntryStub(jsgraph->isolate(), 1).GetCode(),
-        jsgraph->isolate()->factory()->null_value(), sig, source_position_table,
-        runtime_exception_support);
+        jsgraph->isolate()->factory()->null_value(), sig,
+        source_position_table);
     TestBuildingGraphWithBuilder(&builder, zone, sig, start, end);
   }
 }
@@ -422,7 +425,7 @@ void WasmFunctionCompiler::Build(const byte* start, const byte* end) {
   Handle<SeqOneByteString> wire_bytes(compiled_module->shared()->module_bytes(),
                                       isolate());
 
-  compiler::ModuleEnv module_env = builder_->CreateModuleEnv();
+  ModuleEnv module_env = builder_->CreateModuleEnv();
   ErrorThrower thrower(isolate(), "WasmFunctionCompiler::Build");
   ScopedVector<uint8_t> func_wire_bytes(function_->code.length());
   memcpy(func_wire_bytes.start(),
@@ -436,15 +439,14 @@ void WasmFunctionCompiler::Build(const byte* start, const byte* end) {
 
   FunctionBody func_body{function_->sig, function_->code.offset(),
                          func_wire_bytes.start(), func_wire_bytes.end()};
-  compiler::WasmCompilationUnit::CompilationMode comp_mode =
+  WasmCompilationUnit::CompilationMode comp_mode =
       builder_->execution_mode() == WasmExecutionMode::kExecuteLiftoff
-          ? compiler::WasmCompilationUnit::CompilationMode::kLiftoff
-          : compiler::WasmCompilationUnit::CompilationMode::kTurbofan;
-  compiler::WasmCompilationUnit unit(
-      isolate(), &module_env, native_module, func_body, func_name,
-      function_->func_index, CEntryStub(isolate(), 1).GetCode(), comp_mode,
-      isolate()->counters(), builder_->runtime_exception_support(),
-      builder_->lower_simd());
+          ? WasmCompilationUnit::CompilationMode::kLiftoff
+          : WasmCompilationUnit::CompilationMode::kTurbofan;
+  WasmCompilationUnit unit(isolate(), &module_env, native_module, func_body,
+                           func_name, function_->func_index,
+                           CEntryStub(isolate(), 1).GetCode(), comp_mode,
+                           isolate()->counters(), builder_->lower_simd());
   unit.ExecuteCompilation();
   wasm::WasmCode* wasm_code = unit.FinishCompilation(&thrower);
   if (wasm::WasmCode::ShouldBeLogged(isolate())) {

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

@@ -92,7 +92,7 @@ struct ManuallyImportedJSFunction {
 class TestingModuleBuilder {
  public:
   TestingModuleBuilder(Zone*, ManuallyImportedJSFunction*, WasmExecutionMode,
-                       compiler::RuntimeExceptionSupport, LowerSimd);
+                       RuntimeExceptionSupport, LowerSimd);
 
   void ChangeOriginToAsmjs() { test_module_.set_origin(kAsmJsOrigin); }
 
@@ -215,11 +215,11 @@ class TestingModuleBuilder {
     }
   }
 
-  compiler::ModuleEnv CreateModuleEnv();
+  ModuleEnv CreateModuleEnv();
 
   WasmExecutionMode execution_mode() const { return execution_mode_; }
 
-  compiler::RuntimeExceptionSupport runtime_exception_support() const {
+  RuntimeExceptionSupport runtime_exception_support() const {
     return runtime_exception_support_;
   }
 
@@ -236,7 +236,7 @@ class TestingModuleBuilder {
   Handle<WasmInstanceObject> instance_object_;
   NativeModule* native_module_ = nullptr;
   bool linked_ = false;
-  compiler::RuntimeExceptionSupport runtime_exception_support_;
+  RuntimeExceptionSupport runtime_exception_support_;
   LowerSimd lower_simd_;
 
   const WasmGlobal* AddGlobal(ValueType type);
@@ -244,11 +244,10 @@ class TestingModuleBuilder {
   Handle<WasmInstanceObject> InitInstanceObject();
 };
 
-void TestBuildingGraph(
-    Zone* zone, compiler::JSGraph* jsgraph, compiler::ModuleEnv* module,
-    FunctionSig* sig, compiler::SourcePositionTable* source_position_table,
-    const byte* start, const byte* end,
-    compiler::RuntimeExceptionSupport runtime_exception_support);
+void TestBuildingGraph(Zone* zone, compiler::JSGraph* jsgraph,
+                       ModuleEnv* module, FunctionSig* sig,
+                       compiler::SourcePositionTable* source_position_table,
+                       const byte* start, const byte* end);
 
 class WasmFunctionWrapper : private compiler::GraphAndBuilders {
  public:
@@ -348,7 +347,7 @@ class WasmRunnerBase : public HandleAndZoneScope {
  public:
   WasmRunnerBase(ManuallyImportedJSFunction* maybe_import,
                  WasmExecutionMode execution_mode, int num_params,
-                 compiler::RuntimeExceptionSupport runtime_exception_support,
+                 RuntimeExceptionSupport runtime_exception_support,
                  LowerSimd lower_simd)
       : zone_(&allocator_, ZONE_NAME),
         builder_(&zone_, maybe_import, execution_mode,
@@ -431,8 +430,8 @@ class WasmRunner : public WasmRunnerBase {
   WasmRunner(WasmExecutionMode execution_mode,
              ManuallyImportedJSFunction* maybe_import = nullptr,
              const char* main_fn_name = "main",
-             compiler::RuntimeExceptionSupport runtime_exception_support =
-                 compiler::kNoRuntimeExceptionSupport,
+             RuntimeExceptionSupport runtime_exception_support =
+                 kNoRuntimeExceptionSupport,
              LowerSimd lower_simd = kNoLowerSimd)
       : WasmRunnerBase(maybe_import, execution_mode, sizeof...(ParamTypes),
                        runtime_exception_support, lower_simd) {
@@ -443,8 +442,8 @@ class WasmRunner : public WasmRunnerBase {
   }
 
   WasmRunner(WasmExecutionMode execution_mode, LowerSimd lower_simd)
-      : WasmRunner(execution_mode, nullptr, "main",
-                   compiler::kNoRuntimeExceptionSupport, lower_simd) {}
+      : WasmRunner(execution_mode, nullptr, "main", kNoRuntimeExceptionSupport,
+                   lower_simd) {}
 
   ReturnType Call(ParamTypes... p) {
     DCHECK(compiled_);