[turbofan] Teach serializer about soft deopts

When encountering uninitialized feedback, mark the environment as dead
such that we skip over the following bytecodes. Start full processing
again when we reach a bytecode that is either a jump target or an
exception handler entry. For now, don't support this optimization when
compiling for OSR.

Bug: v8:7790
Change-Id: I8177b7fa31ea43d205a2708310b0b0e67302001e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1621930
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61781}

src/base/flags.h

@@ -81,6 +81,8 @@ class Flags final {
   constexpr operator mask_type() const { return mask_; }
   constexpr bool operator!() const { return !mask_; }
 
+  Flags without(flag_type flag) { return *this & (~Flags(flag)); }
+
   friend size_t hash_value(const Flags& flags) { return flags.mask_; }
 
  private:

src/compiler/pipeline.cc

@@ -1249,9 +1249,19 @@ struct SerializationPhase {
   static const char* phase_name() { return "V8.TFSerializeBytecode"; }
 
   void Run(PipelineData* data, Zone* temp_zone) {
+    SerializerForBackgroundCompilationFlags flags;
+    if (data->info()->is_bailout_on_uninitialized()) {
+      flags |= SerializerForBackgroundCompilationFlag::kBailoutOnUninitialized;
+    }
+    if (data->info()->is_source_positions_enabled()) {
+      flags |= SerializerForBackgroundCompilationFlag::kCollectSourcePositions;
+    }
+    if (data->info()->is_osr()) {
+      flags |= SerializerForBackgroundCompilationFlag::kOsr;
+    }
     SerializerForBackgroundCompilation serializer(
         data->broker(), data->dependencies(), temp_zone,
-        data->info()->closure(), data->info()->is_source_positions_enabled());
+        data->info()->closure(), flags);
     serializer.Run();
   }
 };

src/compiler/serializer-for-background-compilation.h

@@ -263,29 +263,37 @@ class Hints {
   MapsSet maps_;
   BlueprintsSet function_blueprints_;
 };
-
 using HintsVector = ZoneVector<Hints>;
 
+enum class SerializerForBackgroundCompilationFlag : uint8_t {
+  kBailoutOnUninitialized = 1 << 0,
+  kCollectSourcePositions = 1 << 1,
+  kOsr = 1 << 2,
+};
+using SerializerForBackgroundCompilationFlags =
+    base::Flags<SerializerForBackgroundCompilationFlag>;
+
 // The SerializerForBackgroundCompilation makes sure that the relevant function
 // data such as bytecode, SharedFunctionInfo and FeedbackVector, used by later
 // optimizations in the compiler, is copied to the heap broker.
 class SerializerForBackgroundCompilation {
  public:
-  SerializerForBackgroundCompilation(JSHeapBroker* broker,
-                                     CompilationDependencies* dependencies,
-                                     Zone* zone, Handle<JSFunction> closure,
-                                     bool collect_source_positions);
+  SerializerForBackgroundCompilation(
+      JSHeapBroker* broker, CompilationDependencies* dependencies, Zone* zone,
+      Handle<JSFunction> closure,
+      SerializerForBackgroundCompilationFlags flags);
   Hints Run();  // NOTE: Returns empty for an already-serialized function.
 
   class Environment;
 
  private:
-  SerializerForBackgroundCompilation(JSHeapBroker* broker,
-                                     CompilationDependencies* dependencies,
-                                     Zone* zone, CompilationSubject function,
-                                     base::Optional<Hints> new_target,
-                                     const HintsVector& arguments,
-                                     bool collect_source_positions);
+  SerializerForBackgroundCompilation(
+      JSHeapBroker* broker, CompilationDependencies* dependencies, Zone* zone,
+      CompilationSubject function, base::Optional<Hints> new_target,
+      const HintsVector& arguments,
+      SerializerForBackgroundCompilationFlags flags);
+
+  bool BailoutOnUninitialized(FeedbackSlot slot);
 
   void TraverseBytecode();
 
@@ -327,17 +335,15 @@ class SerializerForBackgroundCompilation {
   JSHeapBroker* broker() const { return broker_; }
   CompilationDependencies* dependencies() const { return dependencies_; }
   Zone* zone() const { return zone_; }
-  // The following flag is initialized from OptimizedCompilationInfo's
-  // {is_source_positions_enabled}.
-  bool collect_source_positions() const { return collect_source_positions_; }
   Environment* environment() const { return environment_; }
+  SerializerForBackgroundCompilationFlags flags() const { return flags_; }
 
   JSHeapBroker* const broker_;
   CompilationDependencies* const dependencies_;
   Zone* const zone_;
-  bool const collect_source_positions_;
   Environment* const environment_;
   ZoneUnorderedMap<int, Environment*> stashed_environments_;
+  SerializerForBackgroundCompilationFlags const flags_;
 };
 
 }  // namespace compiler