[compiler] Remember start source position in pipeline job preparation.

... so that it can be used during off-thread code assembly.

R=bmeurer@chromium.org

Bug: v8:6048
Change-Id: Iaa9b534b23d02da69c2b2395c1eacfdcffb3ac2f
Reviewed-on: https://chromium-review.googlesource.com/561677Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46455}

src/compiler/code-generator.cc

@@ -37,7 +37,8 @@ class CodeGenerator::JumpTable final : public ZoneObject {
 
 CodeGenerator::CodeGenerator(Frame* frame, Linkage* linkage,
                              InstructionSequence* code, CompilationInfo* info,
-                             base::Optional<OsrHelper> osr_helper)
+                             base::Optional<OsrHelper> osr_helper,
+                             int start_source_position)
     : frame_access_state_(nullptr),
       linkage_(linkage),
       code_(code),
@@ -45,6 +46,7 @@ CodeGenerator::CodeGenerator(Frame* frame, Linkage* linkage,
       info_(info),
       labels_(zone()->NewArray<Label>(code->InstructionBlockCount())),
       current_block_(RpoNumber::Invalid()),
+      start_source_position_(start_source_position),
       current_source_position_(SourcePosition::Unknown()),
       masm_(info->isolate(), nullptr, 0, CodeObjectRequired::kNo),
       resolver_(this),
@@ -87,8 +89,7 @@ void CodeGenerator::AssembleCode() {
   FrameScope frame_scope(masm(), StackFrame::MANUAL);
 
   if (info->is_source_positions_enabled()) {
-    SourcePosition source_position(info->shared_info()->start_position());
-    AssembleSourcePosition(source_position);
+    AssembleSourcePosition(start_source_position());
   }
 
   // Place function entry hook if requested to do so.

src/compiler/code-generator.h

@@ -81,7 +81,8 @@ class CodeGenerator final : public GapResolver::Assembler {
  public:
   explicit CodeGenerator(Frame* frame, Linkage* linkage,
                          InstructionSequence* code, CompilationInfo* info,
-                         base::Optional<OsrHelper> osr_helper);
+                         base::Optional<OsrHelper> osr_helper,
+                         int start_source_position);
 
   // Generate native code. After calling AssembleCode, call FinalizeCode to
   // produce the actual code object. If an error occurs during either phase,
@@ -97,8 +98,11 @@ class CodeGenerator final : public GapResolver::Assembler {
 
   Label* GetLabel(RpoNumber rpo) { return &labels_[rpo.ToSize()]; }
 
-  void AssembleSourcePosition(Instruction* instr);
+  SourcePosition start_source_position() const {
+    return start_source_position_;
+  }
 
+  void AssembleSourcePosition(Instruction* instr);
   void AssembleSourcePosition(SourcePosition source_position);
 
   // Record a safepoint with the given pointer map.
@@ -309,6 +313,7 @@ class CodeGenerator final : public GapResolver::Assembler {
   Label* const labels_;
   Label return_label_;
   RpoNumber current_block_;
+  SourcePosition start_source_position_;
   SourcePosition current_source_position_;
   MacroAssembler masm_;
   GapResolver resolver_;

src/compiler/pipeline.cc

@@ -325,10 +325,15 @@ class PipelineData {
     osr_helper_.emplace(info());
   }
 
+  void set_start_source_position(int position) {
+    DCHECK_EQ(start_source_position_, kNoSourcePosition);
+    start_source_position_ = position;
+  }
+
   void InitializeCodeGenerator(Linkage* linkage) {
     DCHECK_NULL(code_generator_);
-    code_generator_ =
-        new CodeGenerator(frame(), linkage, sequence(), info(), osr_helper_);
+    code_generator_ = new CodeGenerator(frame(), linkage, sequence(), info(),
+                                        osr_helper_, start_source_position_);
   }
 
   void BeginPhaseKind(const char* phase_kind_name) {
@@ -355,6 +360,7 @@ class PipelineData {
   bool compilation_failed_ = false;
   bool verify_graph_ = false;
   bool is_asm_ = false;
+  int start_source_position_ = kNoSourcePosition;
   base::Optional<OsrHelper> osr_helper_;
   Handle<Code> code_ = Handle<Code>::null();
   CodeGenerator* code_generator_ = nullptr;
@@ -630,6 +636,8 @@ PipelineCompilationJob::Status PipelineCompilationJob::PrepareJobImpl() {
     info()->MarkAsInliningEnabled();
   }
 
+  data_.set_start_source_position(info()->shared_info()->start_position());
+
   linkage_ = new (info()->zone())
       Linkage(Linkage::ComputeIncoming(info()->zone(), info()));