[turbofan] Allow to disable liveness analysis in CompilationInfo.

This way we can teach the debugger to disable liveness analysis when
running with (potential) breakpoints, so that the developers always
have (read) access to all scoped variable values.

Bug: v8:7608, chromium:826613
Change-Id: I7e6cea105f111c99d2620546144201624dfe1d8b
Reviewed-on: https://chromium-review.googlesource.com/985838Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52293}

src/compilation-info.cc

@@ -48,6 +48,11 @@ CompilationInfo::CompilationInfo(Zone* zone, Isolate* isolate,
   if (!FLAG_turbo_disable_switch_jump_table) SetFlag(kSwitchJumpTableEnabled);
   if (FLAG_untrusted_code_mitigations) MarkAsPoisoningRegisterArguments();
 
+  // TODO(yangguo): Disable this in case of debugging for crbug.com/826613
+  if (FLAG_analyze_environment_liveness) {
+    MarkAsAnalyzeEnvironmentLiveness();
+  }
+
   // Collect source positions for optimized code when profiling or if debugger
   // is active, to be able to get more precise source positions at the price of
   // more memory consumption.

src/compilation-info.h

@@ -55,7 +55,8 @@ class V8_EXPORT_PRIVATE CompilationInfo final {
     kSwitchJumpTableEnabled = 1 << 13,
     kCalledWithCodeStartRegister = 1 << 14,
     kPoisonRegisterArguments = 1 << 15,
-    kAllocationFoldingEnabled = 1 << 16
+    kAllocationFoldingEnabled = 1 << 16,
+    kAnalyzeEnvironmentLiveness = 1 << 17,
   };
 
   // TODO(mtrofin): investigate if this might be generalized outside wasm, with
@@ -200,6 +201,13 @@ class V8_EXPORT_PRIVATE CompilationInfo final {
     return GetFlag(kAllocationFoldingEnabled);
   }
 
+  void MarkAsAnalyzeEnvironmentLiveness() {
+    SetFlag(kAnalyzeEnvironmentLiveness);
+  }
+  bool is_analyze_environment_liveness() const {
+    return GetFlag(kAnalyzeEnvironmentLiveness);
+  }
+
   // Code getters and setters.
 
   void SetCode(Handle<Code> code) { code_ = code; }

src/compiler/bytecode-graph-builder.cc

@@ -516,7 +516,8 @@ BytecodeGraphBuilder::BytecodeGraphBuilder(
     Handle<FeedbackVector> feedback_vector, BailoutId osr_offset,
     JSGraph* jsgraph, CallFrequency invocation_frequency,
     SourcePositionTable* source_positions, Handle<Context> native_context,
-    int inlining_id, JSTypeHintLowering::Flags flags, bool stack_check)
+    int inlining_id, JSTypeHintLowering::Flags flags, bool stack_check,
+    bool analyze_environment_liveness)
     : local_zone_(local_zone),
       jsgraph_(jsgraph),
       invocation_frequency_(invocation_frequency),
@@ -533,6 +534,7 @@ BytecodeGraphBuilder::BytecodeGraphBuilder(
       osr_offset_(osr_offset),
       currently_peeled_loop_offset_(-1),
       stack_check_(stack_check),
+      analyze_environment_liveness_(analyze_environment_liveness),
       merge_environments_(local_zone),
       generator_merge_environments_(local_zone),
       exception_handlers_(local_zone),
@@ -869,7 +871,7 @@ void BytecodeGraphBuilder::VisitSingleBytecode(
 
 void BytecodeGraphBuilder::VisitBytecodes() {
   BytecodeAnalysis bytecode_analysis(bytecode_array(), local_zone(),
-                                     FLAG_analyze_environment_liveness);
+                                     analyze_environment_liveness());
   bytecode_analysis.Analyze(osr_offset_);
   set_bytecode_analysis(&bytecode_analysis);
 
@@ -878,7 +880,7 @@ void BytecodeGraphBuilder::VisitBytecodes() {
   SourcePositionTableIterator source_position_iterator(
       handle(bytecode_array()->SourcePositionTable()));
 
-  if (FLAG_trace_environment_liveness) {
+  if (analyze_environment_liveness() && FLAG_trace_environment_liveness) {
     OFStream of(stdout);
 
     bytecode_analysis.PrintLivenessTo(of);

src/compiler/bytecode-graph-builder.h

@@ -35,7 +35,7 @@ class BytecodeGraphBuilder {
       SourcePositionTable* source_positions, Handle<Context> native_context,
       int inlining_id = SourcePosition::kNotInlined,
       JSTypeHintLowering::Flags flags = JSTypeHintLowering::kNoFlags,
-      bool stack_check = true);
+      bool stack_check = true, bool analyze_environment_liveness = true);
 
   // Creates a graph by visiting bytecodes.
   void CreateGraph();
@@ -349,6 +349,10 @@ class BytecodeGraphBuilder {
 
   void set_stack_check(bool stack_check) { stack_check_ = stack_check; }
 
+  bool analyze_environment_liveness() const {
+    return analyze_environment_liveness_;
+  }
+
   int current_exception_handler() { return current_exception_handler_; }
 
   void set_current_exception_handler(int index) {
@@ -379,6 +383,7 @@ class BytecodeGraphBuilder {
   BailoutId osr_offset_;
   int currently_peeled_loop_offset_;
   bool stack_check_;
+  bool analyze_environment_liveness_;
 
   // Merge environments are snapshots of the environment at points where the
   // control flow merges. This models a forward data flow propagation of all

src/compiler/js-inlining.cc

@@ -489,7 +489,7 @@ Reduction JSInliner::ReduceJSCall(Node* node) {
     BytecodeGraphBuilder graph_builder(
         zone(), shared_info, feedback_vector, BailoutId::None(), jsgraph(),
         call.frequency(), source_positions_, native_context(), inlining_id,
-        flags, false);
+        flags, false, info_->is_analyze_environment_liveness());
     graph_builder.CreateGraph();
 
     // Extract the inlinee start/end nodes.

src/compiler/pipeline.cc

@@ -1062,7 +1062,8 @@ struct GraphBuilderPhase {
         handle(data->info()->closure()->feedback_vector()),
         data->info()->osr_offset(), data->jsgraph(), CallFrequency(1.0f),
         data->source_positions(), data->native_context(),
-        SourcePosition::kNotInlined, flags);
+        SourcePosition::kNotInlined, flags, true,
+        data->info()->is_analyze_environment_liveness());
     graph_builder.CreateGraph();
   }
 };