[debugger] Ensure at least one breakable position per function.

The function literal consists of a list of statements. Each statement
is associated with a statement position including break location. The
only exception to this rule is when the function immediately throws if
scope resolution found an illegal redeclaration. Make sure that we add a
break location for this case as well. The debugger relies on this.

R=bmeurer@chromium.org, vogelheim@chromium.org
BUG=v8:4690
LOG=N

Review URL: https://codereview.chromium.org/1759603002

Cr-Commit-Position: refs/heads/master@{#34422}

src/debug/debug.cc

@@ -98,7 +98,9 @@ BreakLocation::CodeIterator::CodeIterator(Handle<DebugInfo> debug_info,
     : Iterator(debug_info),
       reloc_iterator_(debug_info->abstract_code()->GetCode(),
                       GetModeMask(type)) {
-  if (!Done()) Next();
+  // There is at least one break location.
+  DCHECK(!Done());
+  Next();
 }
 
 int BreakLocation::CodeIterator::GetModeMask(BreakLocatorType type) {
@@ -179,7 +181,9 @@ BreakLocation::BytecodeArrayIterator::BytecodeArrayIterator(
                                     ->source_position_table()),
       break_locator_type_(type),
       start_position_(debug_info->shared()->start_position()) {
-  if (!Done()) Next();
+  // There is at least one break location.
+  DCHECK(!Done());
+  Next();
 }
 
 void BreakLocation::BytecodeArrayIterator::Next() {

src/full-codegen/arm/full-codegen-arm.cc

@@ -296,9 +296,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/arm64/full-codegen-arm64.cc

@@ -299,9 +299,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/full-codegen.cc

@@ -984,6 +984,13 @@ void FullCodeGenerator::EmitBreak(Statement* target) {
   __ jmp(current->AsBreakable()->break_label());
 }
 
+void FullCodeGenerator::EmitIllegalRedeclaration() {
+  Comment cmnt(masm_, "[ Declarations");
+  Expression* illegal = scope()->GetIllegalRedeclaration();
+  SetExpressionAsStatementPosition(illegal);
+  VisitForEffect(illegal);
+}
+
 void FullCodeGenerator::VisitBreakStatement(BreakStatement* stmt) {
   Comment cmnt(masm_, "[ BreakStatement");
   SetStatementPosition(stmt);

src/full-codegen/full-codegen.h

@@ -684,6 +684,8 @@ class FullCodeGenerator: public AstVisitor {
   void EmitContinue(Statement* target);
   void EmitBreak(Statement* target);
 
+  void EmitIllegalRedeclaration();
+
   // Loop nesting counter.
   int loop_depth() { return loop_depth_; }
   void increment_loop_depth() { loop_depth_++; }

src/full-codegen/ia32/full-codegen-ia32.cc

@@ -291,9 +291,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/mips/full-codegen-mips.cc

@@ -306,9 +306,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/mips64/full-codegen-mips64.cc

@@ -304,9 +304,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/ppc/full-codegen-ppc.cc

@@ -302,9 +302,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     {

src/full-codegen/x64/full-codegen-x64.cc

@@ -287,9 +287,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/full-codegen/x87/full-codegen-x87.cc

@@ -288,9 +288,7 @@ void FullCodeGenerator::Generate() {
   // Visit the declarations and body unless there is an illegal
   // redeclaration.
   if (scope()->HasIllegalRedeclaration()) {
-    Comment cmnt(masm_, "[ Declarations");
+    EmitIllegalRedeclaration();
-    VisitForEffect(scope()->GetIllegalRedeclaration());
-
   } else {
     PrepareForBailoutForId(BailoutId::FunctionEntry(), NO_REGISTERS);
     { Comment cmnt(masm_, "[ Declarations");

src/interpreter/bytecode-array-builder.cc

@@ -1212,6 +1212,13 @@ void BytecodeArrayBuilder::SetExpressionPosition(Expression* expr) {
                                                        expr->position());
 }
 
+void BytecodeArrayBuilder::SetExpressionAsStatementPosition(Expression* expr) {
+  if (expr->position() == RelocInfo::kNoPosition) return;
+  if (exit_seen_in_block_) return;
+  source_position_table_builder_.AddStatementPosition(bytecodes_.size(),
+                                                      expr->position());
+}
+
 bool BytecodeArrayBuilder::TemporaryRegisterIsLive(Register reg) const {
   return temporary_register_allocator()->RegisterIsLive(reg);
 }

src/interpreter/bytecode-array-builder.h

@@ -263,6 +263,7 @@ class BytecodeArrayBuilder final : public ZoneObject, private RegisterMover {
 
   void SetStatementPosition(Statement* stmt);
   void SetExpressionPosition(Expression* expr);
+  void SetExpressionAsStatementPosition(Expression* expr);
 
   // Accessors
   Zone* zone() const { return zone_; }

src/interpreter/bytecode-generator.cc

@@ -620,7 +620,9 @@ void BytecodeGenerator::MakeBytecodeBody() {
 
   // Visit illegal re-declaration and bail out if it exists.
   if (scope()->HasIllegalRedeclaration()) {
-    VisitForEffect(scope()->GetIllegalRedeclaration());
+    Expression* illegal = scope()->GetIllegalRedeclaration();
+    builder()->SetExpressionAsStatementPosition(illegal);
+    VisitForEffect(illegal);
     return;
   }
 

src/interpreter/source-position-table.cc

@@ -151,9 +151,10 @@ void SourcePositionTableBuilder::AddEntry(const PositionTableEntry& entry) {
 }
 
 Handle<ByteArray> SourcePositionTableBuilder::ToSourcePositionTable() {
+  if (bytes_.empty()) return isolate_->factory()->empty_byte_array();
+
   Handle<ByteArray> table = isolate_->factory()->NewByteArray(
       static_cast<int>(bytes_.size()), TENURED);
-  if (bytes_.empty()) return table;
 
   MemCopy(table->GetDataStartAddress(), &*bytes_.begin(), bytes_.size());
 

test/mjsunit/mjsunit.status

@@ -790,7 +790,6 @@
   'es6/debug-stepin-string-template': [FAIL],
   'es6/debug-promises/stepin-constructor': [FAIL],
   'harmony/debug-stepin-proxies': [FAIL],
-  'regress/regress-debugger-redirect': [PASS, FAIL],
   'regress/regress-crbug-119800': [FAIL],
   'regress/regress-crbug-467180': [FAIL],
   'regress/regress-opt-after-debug-deopt': [FAIL],