[coverage] Block coverage with support for IfStatements

src/interpreter/bytecode-generator.h

Index: src/interpreter/bytecode-generator.h
diff --git a/src/interpreter/bytecode-generator.h b/src/interpreter/bytecode-generator.h
index 579365952b9fae9bd4fc51e4c902c0b8bd0c4133..c145a1e1c230d04a6cb699e53ae0b7e7c40e5202 100644
--- a/src/interpreter/bytecode-generator.h
+++ b/src/interpreter/bytecode-generator.h
@@ -236,6 +236,22 @@ class BytecodeGenerator final : public AstVisitor<BytecodeGenerator> {
   inline LanguageMode language_mode() const;
   int feedback_index(FeedbackSlot slot) const;
 
+  bool is_block_coverage() const;
+  static const int kNoCoverageArraySlot = -1;
+  int AllocateBlockCoverageSlot(SourceRange range) {
+    if (!is_block_coverage() || range.IsEmpty()) {
+      return kNoCoverageArraySlot;
+    }
+    const int slot = static_cast<int>(block_coverage_slots_.size());
+    block_coverage_slots_.emplace_back(range);
+    return slot;
+  }
+  void IncBlockCounter(int coverage_array_slot) {
+    if (coverage_array_slot == kNoCoverageArraySlot) return;
+    DCHECK(is_block_coverage());
+    builder()->IncBlockCounter(coverage_array_slot);
+  }

[rmcilroy, 2017/06/01 14:01:50]

I still have this comment here which was unanswered on the previous patchset:

How about factoring this out into a small helper class (similar to
GlobalDeclarationBuilder) and just create the builder in the BytecodeGenerator's
constructor if:
  FLAG_block_coverage && info()->parse_info()->script()->IsUserJavaScript()

then just check for:
  if (block_coverage_builder())
block_coverage_builder()->IncrementBlock(SourceRange range);

in the if / else visitor, then you don't need a is_block_coverage() function,
and we don't have the overhead of an empty ZoneVector when block coverage is
turned off. WDYT?

[jgruber, 2017/06/02 06:39:27]

Sorry I missed that one. I'm happy to factor out into a helper class, but I'd
like to avoid the

if (block_coverage_builder())
  block_coverage_builder()->IncrementBlock(...);

pattern. How do you like the solution the current PS (helper class + 2 helper
methods on BytecodeGenerator)?

+
   Zone* zone_;
   BytecodeArrayBuilder* builder_;
   CompilationInfo* info_;
@@ -251,6 +267,10 @@ class BytecodeGenerator final : public AstVisitor<BytecodeGenerator> {
   ZoneVector<std::pair<ObjectLiteral*, size_t>> object_literals_;
   ZoneVector<std::pair<ArrayLiteral*, size_t>> array_literals_;
 
+  // Contains source range information for allocated block coverage counter
+  // slots. Slot i covers range block_coverage_slots_[i].
+  ZoneVector<SourceRange> block_coverage_slots_;
+
   ControlScope* execution_control_;
   ContextScope* execution_context_;
   ExpressionResultScope* execution_result_;