[coverage] Block coverage with support for IfStatements

src/interpreter/bytecode-generator.h

 // Copyright 2015 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_INTERPRETER_BYTECODE_GENERATOR_H_
 #define V8_INTERPRETER_BYTECODE_GENERATOR_H_
 
 #include "src/ast/ast.h"
 #include "src/interpreter/bytecode-array-builder.h"
 #include "src/interpreter/bytecode-label.h"
@@ skipping 203 matching lines @@
     return builder()->register_allocator();
   }
 
   GlobalDeclarationsBuilder* globals_builder() {
     DCHECK_NOT_NULL(globals_builder_);
     return globals_builder_;
   }
   inline LanguageMode language_mode() const;
   int feedback_index(FeedbackSlot slot) const;
 
+  bool is_block_coverage() const;
+  int AllocateBlockCoverageSlot(SourceRange range) {
+    const int slot = static_cast<int>(block_coverage_slots_.size());
+    block_coverage_slots_.emplace_back(range);
+    return slot;
+  }
+  void IncBlockCounter(SourceRange range) {
+    if (is_block_coverage()) {
+      builder()->IncBlockCounter(AllocateBlockCoverageSlot(range));
+    }
+  }

[rmcilroy, 2017/05/18 14:17:59]

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?

+
   Zone* zone_;
   BytecodeArrayBuilder* builder_;
   CompilationInfo* info_;
   const AstStringConstants* ast_string_constants_;
   DeclarationScope* closure_scope_;
   Scope* current_scope_;
 
   GlobalDeclarationsBuilder* globals_builder_;
   ZoneVector<GlobalDeclarationsBuilder*> global_declarations_;
   ZoneVector<std::pair<FunctionLiteral*, size_t>> function_literals_;
   ZoneVector<std::pair<NativeFunctionLiteral*, size_t>>
       native_function_literals_;
   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_;
 
   BytecodeJumpTable* generator_jump_table_;
   Register generator_state_;
   int loop_depth_;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_GENERATOR_H_