[coverage] Add continuation counters

Track execution counts of the continuations of block structures (e.g.
IfStatements) to capture cases in which execution does not continue after a
block. For example:

for (;;) {
  return;
}
// Never reached, tracked by continuation counter.

A continuation counter only has a start position; it's range is implicitly
until the next sibling range or the end of the parent range.

Bug: v8:6000
Change-Id: I8e8f1f5b140b64c86754b916e626eb50f0707d70
Reviewed-on: https://chromium-review.googlesource.com/530846
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46006}

BUILD.gn

@@ -1678,6 +1678,7 @@ v8_source_set("v8_base") {
     "src/identity-map.h",
     "src/interface-descriptors.cc",
     "src/interface-descriptors.h",
+    "src/interpreter/block-coverage-builder.h",
     "src/interpreter/bytecode-array-accessor.cc",
     "src/interpreter/bytecode-array-accessor.h",
     "src/interpreter/bytecode-array-builder.cc",

src/ast/ast.h

@@ -182,8 +182,13 @@ class AstProperties final BASE_EMBEDDED {
 DEFINE_OPERATORS_FOR_FLAGS(AstProperties::Flags)
 
 struct SourceRange {
-  SourceRange() : start(kNoSourcePosition), end(kNoSourcePosition) {}
+  SourceRange() : SourceRange(kNoSourcePosition, kNoSourcePosition) {}
+  SourceRange(int start, int end) : start(start), end(end) {}
   bool IsEmpty() const { return start == kNoSourcePosition; }
+  static SourceRange ContinuationOf(const SourceRange& that) {
+    return that.IsEmpty() ? SourceRange()
+                          : SourceRange(that.end + 1, kNoSourcePosition);
+  }
   int32_t start, end;
 };
 
@@ -495,6 +500,9 @@ class IterationStatement : public BreakableStatement {
   void set_body(Statement* s) { body_ = s; }
 
   SourceRange body_range() const { return body_range_; }
+  SourceRange continuation_range() const {
+    return SourceRange::ContinuationOf(body_range_);
+  }
 
   int suspend_count() const { return suspend_count_; }
   int first_suspend_id() const { return first_suspend_id_; }
@@ -922,6 +930,11 @@ class IfStatement final : public Statement {
 
   SourceRange then_range() const { return then_range_; }
   SourceRange else_range() const { return else_range_; }
+  SourceRange continuation_range() const {
+    SourceRange trailing_range =
+        HasElseStatement() ? else_range() : then_range();
+    return SourceRange::ContinuationOf(trailing_range);
+  }
 
   void set_condition(Expression* e) { condition_ = e; }
   void set_then_statement(Statement* s) { then_statement_ = s; }

src/debug/debug-coverage.cc

@@ -4,6 +4,7 @@
 
 #include "src/debug/debug-coverage.h"
 
+#include "src/ast/ast.h"
 #include "src/base/hashmap.h"
 #include "src/deoptimizer.h"
 #include "src/frames-inl.h"
@@ -59,8 +60,8 @@ bool CompareSharedFunctionInfo(SharedFunctionInfo* a, SharedFunctionInfo* b) {
 }
 
 bool CompareCoverageBlock(const CoverageBlock& a, const CoverageBlock& b) {
-  DCHECK(a.start != kNoSourcePosition && a.end != kNoSourcePosition);
-  DCHECK(b.start != kNoSourcePosition && b.end != kNoSourcePosition);
+  DCHECK(a.start != kNoSourcePosition);
+  DCHECK(b.start != kNoSourcePosition);
   if (a.start == b.start) return a.end > b.end;
   return a.start < b.start;
 }
@@ -81,8 +82,6 @@ std::vector<CoverageBlock> GetSortedBlockData(Isolate* isolate,
     const int count = coverage_info->BlockCount(i);
 
     DCHECK(start_pos != kNoSourcePosition);
-    DCHECK(until_pos != kNoSourcePosition);
-
     result.emplace_back(start_pos, until_pos, count);
   }
 
@@ -91,6 +90,44 @@ std::vector<CoverageBlock> GetSortedBlockData(Isolate* isolate,
 
   return result;
 }
+
+// Rewrite position singletons (produced by unconditional control flow
+// like return statements, and by continuation counters) into source
+// ranges that end at the next sibling range or the end of the parent
+// range, whichever comes first.
+void RewritePositionSingletonsToRanges(CoverageFunction* function) {
+  std::vector<SourceRange> nesting_stack;
+  nesting_stack.emplace_back(function->start, function->end);
+
+  const int blocks_count = static_cast<int>(function->blocks.size());
+  for (int i = 0; i < blocks_count; i++) {
+    CoverageBlock& block = function->blocks[i];
+
+    while (nesting_stack.back().end < block.start) {
+      nesting_stack.pop_back();
+    }
+
+    const SourceRange& parent_range = nesting_stack.back();
+
+    DCHECK(block.start != kNoSourcePosition);
+    if (block.end == kNoSourcePosition) {
+      // The current block ends at the next sibling block (if it exists) or the
+      // end of the parent block otherwise.
+      if (i < blocks_count - 1 &&
+          function->blocks[i + 1].start <= parent_range.end) {
+        block.end = function->blocks[i + 1].start - 1;
+      } else {
+        block.end = parent_range.end;
+      }
+    }
+
+    if (i < blocks_count - 1) {
+      nesting_stack.emplace_back(block.start, block.end);
+    }
+  }
+
+  DCHECK_EQ(1, nesting_stack.size());
+}
 }  // anonymous namespace
 
 Coverage* Coverage::CollectPrecise(Isolate* isolate) {
@@ -207,6 +244,7 @@ Coverage* Coverage::Collect(Isolate* isolate,
         if (FLAG_block_coverage && info->HasCoverageInfo()) {
           CoverageFunction* function = &functions->back();
           function->blocks = GetSortedBlockData(isolate, info);
+          RewritePositionSingletonsToRanges(function);
         }
       }
     }

src/interpreter/block-coverage-builder.h

+// Copyright 2017 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_BLOCK_COVERAGE_BUILDER_H_
+#define V8_INTERPRETER_BLOCK_COVERAGE_BUILDER_H_
+
+#include "src/ast/ast.h"
+#include "src/interpreter/bytecode-array-builder.h"
+
+#include "src/zone/zone-containers.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+// Used to generate IncBlockCounter bytecodes and the {source range, slot}
+// mapping for block coverage.
+class BlockCoverageBuilder final : public ZoneObject {
+ public:
+  BlockCoverageBuilder(Zone* zone, BytecodeArrayBuilder* builder)
+      : slots_(0, zone), builder_(builder) {}
+
+  static const int kNoCoverageArraySlot = -1;
+
+  int AllocateBlockCoverageSlot(SourceRange range) {
+    if (range.IsEmpty()) return kNoCoverageArraySlot;
+    const int slot = static_cast<int>(slots_.size());
+    slots_.emplace_back(range);
+    return slot;
+  }
+
+  void IncrementBlockCounter(int coverage_array_slot) {
+    if (coverage_array_slot == kNoCoverageArraySlot) return;
+    builder_->IncBlockCounter(coverage_array_slot);
+  }
+
+  const ZoneVector<SourceRange>& slots() const { return slots_; }
+
+ private:
+  // Contains source range information for allocated block coverage counter
+  // slots. Slot i covers range slots_[i].
+  ZoneVector<SourceRange> slots_;
+  BytecodeArrayBuilder* builder_;
+};
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_INTERPRETER_BLOCK_COVERAGE_BUILDER_H_

src/interpreter/bytecode-generator.cc

@@ -737,36 +737,6 @@ class BytecodeGenerator::GlobalDeclarationsBuilder final : public ZoneObject {
   bool has_constant_pool_entry_;
 };
 
-// Used to generate IncBlockCounter bytecodes and the {source range, slot}
-// mapping for block coverage.
-class BytecodeGenerator::BlockCoverageBuilder final : public ZoneObject {
- public:
-  explicit BlockCoverageBuilder(Zone* zone, BytecodeArrayBuilder* builder)
-      : slots_(0, zone), builder_(builder) {}
-
-  static const int kNoCoverageArraySlot = -1;
-
-  int AllocateBlockCoverageSlot(SourceRange range) {
-    if (range.IsEmpty()) return kNoCoverageArraySlot;
-    const int slot = static_cast<int>(slots_.size());
-    slots_.emplace_back(range);
-    return slot;
-  }
-
-  void IncrementBlockCounter(int coverage_array_slot) {
-    if (coverage_array_slot == kNoCoverageArraySlot) return;
-    builder_->IncBlockCounter(coverage_array_slot);
-  }
-
-  const ZoneVector<SourceRange>& slots() const { return slots_; }
-
- private:
-  // Contains source range information for allocated block coverage counter
-  // slots. Slot i covers range slots_[i].
-  ZoneVector<SourceRange> slots_;
-  BytecodeArrayBuilder* builder_;
-};
-
 class BytecodeGenerator::CurrentScope final {
  public:
   CurrentScope(BytecodeGenerator* generator, Scope* scope)
@@ -1237,6 +1207,8 @@ void BytecodeGenerator::VisitIfStatement(IfStatement* stmt) {
 
   int then_slot = AllocateBlockCoverageSlotIfEnabled(stmt->then_range());
   int else_slot = AllocateBlockCoverageSlotIfEnabled(stmt->else_range());
+  int continuation_slot =
+      AllocateBlockCoverageSlotIfEnabled(stmt->continuation_range());
 
   if (stmt->condition()->ToBooleanIsTrue()) {
     // Generate then block unconditionally as always true.
@@ -1271,6 +1243,7 @@ void BytecodeGenerator::VisitIfStatement(IfStatement* stmt) {
     }
     builder()->Bind(&end_label);
   }
+  BuildIncrementBlockCoverageCounterIfEnabled(continuation_slot);
 }
 
 void BytecodeGenerator::VisitSloppyBlockFunctionStatement(
@@ -1361,6 +1334,7 @@ void BytecodeGenerator::VisitCaseClause(CaseClause* clause) {
 
 void BytecodeGenerator::VisitIterationBody(IterationStatement* stmt,
                                            LoopBuilder* loop_builder) {
+  loop_builder->LoopBody();
   ControlScopeForIteration execution_control(this, stmt, loop_builder);
   builder()->StackCheck(stmt->position());
   Visit(stmt->body());
@@ -1368,20 +1342,16 @@ void BytecodeGenerator::VisitIterationBody(IterationStatement* stmt,
 }
 
 void BytecodeGenerator::VisitDoWhileStatement(DoWhileStatement* stmt) {
-  int body_slot = AllocateBlockCoverageSlotIfEnabled(stmt->body_range());
-
-  LoopBuilder loop_builder(builder());
+  LoopBuilder loop_builder(builder(), block_coverage_builder_,
+                           stmt->body_range(), stmt->continuation_range());
   if (stmt->cond()->ToBooleanIsFalse()) {
-    BuildIncrementBlockCoverageCounterIfEnabled(body_slot);
     VisitIterationBody(stmt, &loop_builder);
   } else if (stmt->cond()->ToBooleanIsTrue()) {
     VisitIterationHeader(stmt, &loop_builder);
-    BuildIncrementBlockCoverageCounterIfEnabled(body_slot);
     VisitIterationBody(stmt, &loop_builder);
     loop_builder.JumpToHeader(loop_depth_);
   } else {
     VisitIterationHeader(stmt, &loop_builder);
-    BuildIncrementBlockCoverageCounterIfEnabled(body_slot);
     VisitIterationBody(stmt, &loop_builder);
     builder()->SetExpressionAsStatementPosition(stmt->cond());
     BytecodeLabels loop_backbranch(zone());
@@ -1393,14 +1363,14 @@ void BytecodeGenerator::VisitDoWhileStatement(DoWhileStatement* stmt) {
 }
 
 void BytecodeGenerator::VisitWhileStatement(WhileStatement* stmt) {
-  int body_slot = AllocateBlockCoverageSlotIfEnabled(stmt->body_range());
+  LoopBuilder loop_builder(builder(), block_coverage_builder_,
+                           stmt->body_range(), stmt->continuation_range());
 
   if (stmt->cond()->ToBooleanIsFalse()) {
     // If the condition is false there is no need to generate the loop.
     return;
   }
 
-  LoopBuilder loop_builder(builder());
   VisitIterationHeader(stmt, &loop_builder);
   if (!stmt->cond()->ToBooleanIsTrue()) {
     builder()->SetExpressionAsStatementPosition(stmt->cond());
@@ -1409,13 +1379,13 @@ void BytecodeGenerator::VisitWhileStatement(WhileStatement* stmt) {
                  TestFallthrough::kThen);
     loop_body.Bind(builder());
   }
-  BuildIncrementBlockCoverageCounterIfEnabled(body_slot);
   VisitIterationBody(stmt, &loop_builder);
   loop_builder.JumpToHeader(loop_depth_);
 }
 
 void BytecodeGenerator::VisitForStatement(ForStatement* stmt) {
-  int body_slot = AllocateBlockCoverageSlotIfEnabled(stmt->body_range());
+  LoopBuilder loop_builder(builder(), block_coverage_builder_,
+                           stmt->body_range(), stmt->continuation_range());
 
   if (stmt->init() != nullptr) {
     Visit(stmt->init());
@@ -1426,7 +1396,6 @@ void BytecodeGenerator::VisitForStatement(ForStatement* stmt) {
     return;
   }
 
-  LoopBuilder loop_builder(builder());
   VisitIterationHeader(stmt, &loop_builder);
   if (stmt->cond() && !stmt->cond()->ToBooleanIsTrue()) {
     builder()->SetExpressionAsStatementPosition(stmt->cond());
@@ -1435,7 +1404,6 @@ void BytecodeGenerator::VisitForStatement(ForStatement* stmt) {
                  TestFallthrough::kThen);
     loop_body.Bind(builder());
   }
-  BuildIncrementBlockCoverageCounterIfEnabled(body_slot);
   VisitIterationBody(stmt, &loop_builder);
   if (stmt->next() != nullptr) {
     builder()->SetStatementPosition(stmt->next());

src/interpreter/bytecode-generator.h

@@ -21,6 +21,7 @@ namespace interpreter {
 
 class GlobalDeclarationsBuilder;
 class LoopBuilder;
+class BlockCoverageBuilder;
 class BytecodeJumpTable;
 
 class BytecodeGenerator final : public AstVisitor<BytecodeGenerator> {
@@ -51,7 +52,6 @@ class BytecodeGenerator final : public AstVisitor<BytecodeGenerator> {
   class ExpressionResultScope;
   class EffectResultScope;
   class GlobalDeclarationsBuilder;
-  class BlockCoverageBuilder;
   class RegisterAllocationScope;
   class TestResultScope;
   class ValueResultScope;

src/interpreter/control-flow-builders.cc

@@ -52,6 +52,11 @@ LoopBuilder::~LoopBuilder() {
   if (generator_jump_table_location_ != nullptr) {
     *generator_jump_table_location_ = parent_generator_jump_table_;
   }
+  // Generate block coverage counter for the continuation.
+  if (block_coverage_builder_ != nullptr) {
+    block_coverage_builder_->IncrementBlockCounter(
+        block_coverage_continuation_slot_);
+  }
 }
 
 void LoopBuilder::LoopHeader() {
@@ -83,6 +88,12 @@ void LoopBuilder::LoopHeaderInGenerator(
       builder()->AllocateJumpTable(resume_count, first_resume_id);
 }
 
+void LoopBuilder::LoopBody() {
+  if (block_coverage_builder_ != nullptr) {
+    block_coverage_builder_->IncrementBlockCounter(block_coverage_body_slot_);
+  }
+}
+
 void LoopBuilder::JumpToHeader(int loop_depth) {
   // Pass the proper loop nesting level to the backwards branch, to trigger
   // on-stack replacement when armed for the given loop nesting depth.

src/interpreter/control-flow-builders.h

@@ -7,6 +7,7 @@
 
 #include "src/interpreter/bytecode-array-builder.h"
 
+#include "src/interpreter/block-coverage-builder.h"
 #include "src/interpreter/bytecode-label.h"
 #include "src/zone/zone-containers.h"
 
@@ -87,16 +88,29 @@ class V8_EXPORT_PRIVATE BlockBuilder final
 // their loop.
 class V8_EXPORT_PRIVATE LoopBuilder final : public BreakableControlFlowBuilder {
  public:
-  explicit LoopBuilder(BytecodeArrayBuilder* builder)
+  LoopBuilder(BytecodeArrayBuilder* builder,
+              BlockCoverageBuilder* block_coverage_builder = nullptr,
+              const SourceRange& body_range = {},
+              const SourceRange& continuation_range = {})
       : BreakableControlFlowBuilder(builder),
         continue_labels_(builder->zone()),
         generator_jump_table_location_(nullptr),
-        parent_generator_jump_table_(nullptr) {}
+        parent_generator_jump_table_(nullptr),
+        block_coverage_builder_(block_coverage_builder) {
+    if (block_coverage_builder_ != nullptr) {
+      block_coverage_body_slot_ =
+          block_coverage_builder_->AllocateBlockCoverageSlot(body_range);
+      block_coverage_continuation_slot_ =
+          block_coverage_builder_->AllocateBlockCoverageSlot(
+              continuation_range);
+    }
+  }
   ~LoopBuilder();
 
   void LoopHeader();
   void LoopHeaderInGenerator(BytecodeJumpTable** parent_generator_jump_table,
                              int first_resume_id, int resume_count);
+  void LoopBody();
   void JumpToHeader(int loop_depth);
   void BindContinueTarget();
 
@@ -120,6 +134,10 @@ class V8_EXPORT_PRIVATE LoopBuilder final : public BreakableControlFlowBuilder {
   // field is ugly, figure out a better way to do this.
   BytecodeJumpTable** generator_jump_table_location_;
   BytecodeJumpTable* parent_generator_jump_table_;
+
+  int block_coverage_body_slot_;
+  int block_coverage_continuation_slot_;
+  BlockCoverageBuilder* block_coverage_builder_;
 };
 
 

src/v8.gyp

@@ -1135,6 +1135,7 @@
         'identity-map.h',
         'interface-descriptors.cc',
         'interface-descriptors.h',
+        'interpreter/block-coverage-builder.h',
         'interpreter/bytecodes.cc',
         'interpreter/bytecodes.h',
         'interpreter/bytecode-array-accessor.cc',

test/mjsunit/code-coverage-block.js

@@ -21,7 +21,7 @@ function TestCoverage(name, source, expectation) {
   var stringified_result = JSON.stringify(covfefe);
   var stringified_expectation = JSON.stringify(expectation);
   if (stringified_result != stringified_expectation) {
-    print(JSON.stringify(covfefe, undefined, 1));
+    print(stringified_result.replace(/[}],[{]/g, "},\n {"));
   }
   assertEquals(stringified_expectation, stringified_result, name + " failed");
 }
@@ -66,16 +66,44 @@ f(43);
  {"start":45,"end":83,"count":1},
  {"start":64,"end":69,"count":0},
  {"start":71,"end":79,"count":1},
+ {"start":80,"end":83,"count":1},
+ {"start":84,"end":97,"count":2},
  {"start":98,"end":107,"count":1},
  {"start":109,"end":121,"count":1},
+ {"start":122,"end":135,"count":2},
  {"start":136,"end":141,"count":1},
  {"start":143,"end":151,"count":1},
+ {"start":152,"end":163,"count":2},
  {"start":164,"end":169,"count":0},
  {"start":171,"end":179,"count":2},
+ {"start":180,"end":191,"count":2},
  {"start":192,"end":197,"count":0},
+ {"start":198,"end":208,"count":2},
  {"start":209,"end":214,"count":2},
  {"start":216,"end":224,"count":0},
- {"start":236,"end":241,"count":2}]
+ {"start":225,"end":235,"count":2},
+ {"start":236,"end":241,"count":2},
+ {"start":242,"end":244,"count":2}]
+);
+
+function nop() {}
+
+TestCoverage(
+"if statement (early return)",
+`
+!function() {                             // 0000
+  if (true) {                             // 0050
+    nop();                                // 0100
+    return;                               // 0150
+    nop();                                // 0200
+  }                                       // 0250
+  nop();                                  // 0300
+}()                                       // 0350
+`,
+[{"start":0,"end":399,"count":1},
+ {"start":1,"end":351,"count":1},
+ {"start":60,"end":252,"count":1},
+ {"start":253,"end":351,"count":0}]
 );
 
 TestCoverage(
@@ -98,12 +126,18 @@ function g() {}
  {"start":0,"end":15,"count":36},
  {"start":17,"end":256,"count":1},
  {"start":59,"end":64,"count":12},
+ {"start":65,"end":94,"count":1},
  {"start":95,"end":110,"count":12},
+ {"start":111,"end":139,"count":1},
  {"start":140,"end":145,"count":0},
+ {"start":146,"end":173,"count":1},
  {"start":174,"end":181,"count":1},
+ {"start":182,"end":211,"count":1},
  {"start":212,"end":253,"count":12},
  {"start":234,"end":239,"count":4},
- {"start":241,"end":249,"count":8}]
+ {"start":241,"end":249,"count":8},
+ {"start":250,"end":253,"count":12},
+ {"start":254,"end":256,"count":1}]
 );
 
 TestCoverage(
@@ -122,9 +156,47 @@ function g() {}
  {"start":0,"end":15,"count":36},
  {"start":17,"end":168,"count":1},
  {"start":72,"end":77,"count":12},
+ {"start":78,"end":109,"count":1},
  {"start":110,"end":115,"count":12},
+ {"start":116,"end":141,"count":1},
  {"start":142,"end":147,"count":12},
- {"start":158,"end":165,"count":1}]
+ {"start":148,"end":157,"count":1},
+ {"start":158,"end":165,"count":1},
+ {"start":166,"end":168,"count":1}]
+);
+
+TestCoverage(
+"for statement (early return)",
+`
+!function() {                             // 0000
+  for (var i = 0; i < 10; i++) {          // 0050
+    nop();                                // 0100
+    continue;                             // 0150
+    nop();                                // 0200
+  }                                       // 0250
+  nop();                                  // 0300
+  for (;;) {                              // 0350
+    nop();                                // 0400
+    break;                                // 0450
+    nop();                                // 0500
+  }                                       // 0550
+  nop();                                  // 0600
+  for (;;) {                              // 0650
+    nop();                                // 0700
+    return;                               // 0750
+    nop();                                // 0800
+  }                                       // 0850
+  nop();                                  // 0900
+}()                                       // 0950
+`,
+[{"start":0,"end":999,"count":1},
+ {"start":1,"end":951,"count":1},
+ {"start":79,"end":252,"count":10},
+ {"start":253,"end":358,"count":1},
+ {"start":359,"end":552,"count":1},
+ {"start":553,"end":658,"count":1},
+ {"start":659,"end":852,"count":1},
+ {"start":853,"end":951,"count":0}]
 );
 
 TestCoverage(
@@ -148,13 +220,91 @@ function g() {}
  {"start":0,"end":15,"count":25},
  {"start":17,"end":313,"count":1},
  {"start":61,"end":66,"count":12},
+ {"start":67,"end":89,"count":1},
  {"start":90,"end":104,"count":12},
+ {"start":105,"end":126,"count":1},
  {"start":127,"end":132,"count":0},
+ {"start":133,"end":153,"count":1},
  {"start":154,"end":161,"count":1},
+ {"start":162,"end":172,"count":1},
  {"start":173,"end":179,"count":12},
+ {"start":180,"end":205,"count":1},
  {"start":206,"end":221,"count":12},
+ {"start":222,"end":247,"count":1},
  {"start":248,"end":258,"count":1},
- {"start":284,"end":296,"count":1}]
+ {"start":259,"end":283,"count":1},
+ {"start":284,"end":296,"count":1},
+ {"start":297,"end":313,"count":1}]
+);
+
+TestCoverage(
+"while statement (early return)",
+`
+!function() {                             // 0000
+  let i = 0;                              // 0050
+  while (i < 10) {                        // 0100
+    i++;                                  // 0150
+    continue;                             // 0200
+    nop();                                // 0250
+  }                                       // 0300
+  nop();                                  // 0350
+  while (true) {                          // 0400
+    nop();                                // 0450
+    break;                                // 0500
+    nop();                                // 0550
+  }                                       // 0600
+  nop();                                  // 0650
+  while (true) {                          // 0700
+    nop();                                // 0750
+    return;                               // 0800
+    nop();                                // 0850
+  }                                       // 0900
+  nop();                                  // 0950
+}()                                       // 1000
+`,
+[{"start":0,"end":1049,"count":1},
+ {"start":1,"end":1001,"count":1},
+ {"start":115,"end":302,"count":10},
+ {"start":303,"end":412,"count":1},
+ {"start":413,"end":602,"count":1},
+ {"start":603,"end":712,"count":1},
+ {"start":713,"end":902,"count":1},
+ {"start":903,"end":1001,"count":0}]
+);
+
+TestCoverage(
+"do-while statement (early return)",
+`
+!function() {                             // 0000
+  let i = 0;                              // 0050
+  do {                                    // 0100
+    i++;                                  // 0150
+    continue;                             // 0200
+    nop();                                // 0250
+  } while (i < 10);                       // 0300
+  nop();                                  // 0350
+  do {                                    // 0400
+    nop();                                // 0450
+    break;                                // 0500
+    nop();                                // 0550
+  } while (true);                         // 0600
+  nop();                                  // 0650
+  do {                                    // 0700
+    nop();                                // 0750
+    return;                               // 0800
+    nop();                                // 0850
+  } while (true);                         // 0900
+  nop();                                  // 0950
+}()                                       // 1000
+`,
+[{"start":0,"end":1049,"count":1},
+ {"start":1,"end":1001,"count":1},
+ {"start":102,"end":302,"count":10},
+ {"start":303,"end":401,"count":1},
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 );
 
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