[parser] Simplify StatementList parsing by splitting out directive parsing

Change-Id: I233a3f6d8b19b945cfc3572d72237ec5619d8cbc
Reviewed-on: https://chromium-review.googlesource.com/c/1307414Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57129}

src/parsing/parser-base.h

@@ -4602,82 +4602,71 @@ ParserBase<Impl>::ParseStatementList(StatementListT body,
   // StatementList ::
   //   (StatementListItem)* <end_token>
 
-  // Allocate a target stack to use for this set of source
-  // elements. This way, all scripts and functions get their own
-  // target stack thus avoiding illegal breaks and continues across
-  // functions.
-  typename Types::TargetScope target_scope(this);
-  int count_statements = 0;
-
   DCHECK(!impl()->IsNull(body));
-  bool directive_prologue = true;  // Parsing directive prologue.
 
-  while (peek() != end_token) {
-    if (directive_prologue && peek() != Token::STRING) {
-      directive_prologue = false;
-    }
-
-    bool starts_with_identifier = peek() == Token::IDENTIFIER;
+  while (peek() == Token::STRING && (scanner()->HasLineTerminatorAfterNext() ||
+                                     Token::IsAutoSemicolon(PeekAhead()))) {
+    const AstRawString* symbol = scanner()->NextSymbol(ast_value_factory_);
     Scanner::Location token_loc = scanner()->peek_location();
-    StatementT stat = ParseStatementListItem();
-    RETURN_IF_PARSE_ERROR_CUSTOM(Return, kLazyParsingComplete)
-
-    if (impl()->IsNull(stat) || stat->IsEmptyStatement()) {
-      directive_prologue = false;  // End of directive prologue.
-      continue;
-    }
-
-    if (directive_prologue) {
-      // The length of the token is used to distinguish between strings literals
-      // that evaluate equal to directives but contain either escape sequences
-      // (e.g., "use \x73trict") or line continuations (e.g., "use \(newline)
-      // strict").
-      if (impl()->IsUseStrictDirective(stat) &&
-          token_loc.end_pos - token_loc.beg_pos == sizeof("use strict") + 1) {
-        // Directive "use strict" (ES5 14.1).
-        RaiseLanguageMode(LanguageMode::kStrict);
-        if (!scope()->HasSimpleParameters()) {
-          // TC39 deemed "use strict" directives to be an error when occurring
-          // in the body of a function with non-simple parameter list, on
-          // 29/7/2015. https://goo.gl/ueA7Ln
-          impl()->ReportMessageAt(
-              token_loc, MessageTemplate::kIllegalLanguageModeDirective,
-              "use strict");
-          return kLazyParsingComplete;
-        }
-      } else if (impl()->IsUseAsmDirective(stat) &&
-                 token_loc.end_pos - token_loc.beg_pos ==
-                     sizeof("use asm") + 1) {
-        // Directive "use asm".
-        impl()->SetAsmModule();
-      } else if (impl()->IsStringLiteral(stat)) {
-        // Possibly an unknown directive.
-        // Should not change mode, but will increment usage counters
-        // as appropriate. Ditto usages below.
-        RaiseLanguageMode(LanguageMode::kSloppy);
-      } else {
-        // End of the directive prologue.
-        directive_prologue = false;
-        RaiseLanguageMode(LanguageMode::kSloppy);
+    // The length of the token is used to distinguish between strings literals
+    // that evaluate equal to directives but contain either escape sequences
+    // (e.g., "use \x73trict") or line continuations (e.g., "use \(newline)
+    // strict").
+    if (symbol == ast_value_factory()->use_strict_string() &&
+        token_loc.end_pos - token_loc.beg_pos == sizeof("use strict") + 1) {
+      // Directive "use strict" (ES5 14.1).
+      RaiseLanguageMode(LanguageMode::kStrict);
+      if (!scope()->HasSimpleParameters()) {
+        // TC39 deemed "use strict" directives to be an error when occurring
+        // in the body of a function with non-simple parameter list, on
+        // 29/7/2015. https://goo.gl/ueA7Ln
+        impl()->ReportMessageAt(token_loc,
+                                MessageTemplate::kIllegalLanguageModeDirective,
+                                "use strict");
+        return kLazyParsingComplete;
       }
+    } else if (symbol == ast_value_factory()->use_asm_string() &&
+               token_loc.end_pos - token_loc.beg_pos == sizeof("use asm") + 1) {
+      // Directive "use asm".
+      impl()->SetAsmModule();
     } else {
+      // Possibly an unknown directive.
+      // Should not change mode, but will increment usage counters
+      // as appropriate. Ditto usages below.
       RaiseLanguageMode(LanguageMode::kSloppy);
     }
+    StatementT stat = ParseStatementListItem();
+    DCHECK(!has_error());
+    body->Add(stat, zone());
+    may_abort = false;
+  }
 
-    // If we're allowed to abort, we will do so when we see a "long and
-    // trivial" function. Our current definition of "long and trivial" is:
-    // - over kLazyParseTrialLimit statements
-    // - all starting with an identifier (i.e., no if, for, while, etc.)
-    if (may_abort) {
-      if (!starts_with_identifier) {
-        may_abort = false;
-      } else if (++count_statements > kLazyParseTrialLimit) {
-        return kLazyParsingAborted;
-      }
+  // Allocate a target stack to use for this set of source elements. This way,
+  // all scripts and functions get their own target stack thus avoiding illegal
+  // breaks and continues across functions.
+  typename Types::TargetScope target_scope(this);
+  int count_statements = 0;
+
+  if (may_abort) {
+    while (peek() == Token::IDENTIFIER) {
+      StatementT stat = ParseStatementListItem();
+      RETURN_IF_PARSE_ERROR_CUSTOM(Return, kLazyParsingComplete);
+      // If we're allowed to abort, we will do so when we see a "long and
+      // trivial" function. Our current definition of "long and trivial" is:
+      // - over kLazyParseTrialLimit statements
+      // - all starting with an identifier (i.e., no if, for, while, etc.)
+      if (++count_statements > kLazyParseTrialLimit) return kLazyParsingAborted;
+      body->Add(stat, zone());
     }
+  }
 
+  while (peek() != end_token) {
+    StatementT stat = ParseStatementListItem();
+    RETURN_IF_PARSE_ERROR_CUSTOM(Return, kLazyParsingComplete)
+    if (impl()->IsNull(stat) || stat->IsEmptyStatement()) continue;
     body->Add(stat, zone());
   }
+
   return kLazyParsingComplete;
 }
 

src/parsing/parser.h

@@ -649,14 +649,6 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     return string->AsArrayIndex(index);
   }
 
-  V8_INLINE bool IsUseStrictDirective(Statement* statement) const {
-    return IsStringLiteral(statement, ast_value_factory()->use_strict_string());
-  }
-
-  V8_INLINE bool IsUseAsmDirective(Statement* statement) const {
-    return IsStringLiteral(statement, ast_value_factory()->use_asm_string());
-  }
-
   // Returns true if the statement is an expression statement containing
   // a single string literal.  If a second argument is given, the literal
   // is also compared with it and the result is true only if they are equal.

src/parsing/preparser.h

@@ -149,16 +149,6 @@ class PreParserExpression {
     return PreParserExpression(TypeField::encode(kStringLiteralExpression));
   }
 
-  static PreParserExpression UseStrictStringLiteral() {
-    return PreParserExpression(TypeField::encode(kStringLiteralExpression) |
-                               IsUseStrictField::encode(true));
-  }
-
-  static PreParserExpression UseAsmStringLiteral() {
-    return PreParserExpression(TypeField::encode(kStringLiteralExpression) |
-                               IsUseAsmField::encode(true));
-  }
-
   static PreParserExpression This() {
     return PreParserExpression(TypeField::encode(kExpression) |
                                ExpressionTypeField::encode(kThisExpression));
@@ -244,16 +234,6 @@ class PreParserExpression {
     return TypeField::decode(code_) == kStringLiteralExpression;
   }
 
-  bool IsUseStrictLiteral() const {
-    return TypeField::decode(code_) == kStringLiteralExpression &&
-           IsUseStrictField::decode(code_);
-  }
-
-  bool IsUseAsmLiteral() const {
-    return TypeField::decode(code_) == kStringLiteralExpression &&
-           IsUseAsmField::decode(code_);
-  }
-
   bool IsThis() const {
     return TypeField::decode(code_) == kExpression &&
            ExpressionTypeField::decode(code_) == kThisExpression;
@@ -389,8 +369,6 @@ class PreParserExpression {
   // The rest of the bits are interpreted depending on the value
   // of the Type field, so they can share the storage.
   typedef BitField<ExpressionType, TypeField::kNext, 4> ExpressionTypeField;
-  typedef BitField<bool, TypeField::kNext, 1> IsUseStrictField;
-  typedef BitField<bool, IsUseStrictField::kNext, 1> IsUseAsmField;
   typedef BitField<PreParserIdentifier::Type, TypeField::kNext, 8>
       IdentifierTypeField;
   typedef BitField<bool, TypeField::kNext, 1> HasCoverInitializedNameField;
@@ -480,28 +458,13 @@ class PreParserStatement {
   // "use strict".
   static PreParserStatement ExpressionStatement(
       const PreParserExpression& expression) {
-    if (expression.IsUseStrictLiteral()) {
-      return PreParserStatement(kUseStrictExpressionStatement);
-    }
-    if (expression.IsUseAsmLiteral()) {
-      return PreParserStatement(kUseAsmExpressionStatement);
-    }
     if (expression.IsStringLiteral()) {
       return PreParserStatement(kStringLiteralExpressionStatement);
     }
     return Default();
   }
 
-  bool IsStringLiteral() {
-    return code_ == kStringLiteralExpressionStatement || IsUseStrictLiteral() ||
-           IsUseAsmLiteral();
-  }
-
-  bool IsUseStrictLiteral() {
-    return code_ == kUseStrictExpressionStatement;
-  }
-
-  bool IsUseAsmLiteral() { return code_ == kUseAsmExpressionStatement; }
+  bool IsStringLiteral() { return code_ == kStringLiteralExpressionStatement; }
 
   bool IsJumpStatement() {
     return code_ == kJumpStatement;
@@ -535,8 +498,6 @@ class PreParserStatement {
     kUnknownStatement,
     kJumpStatement,
     kStringLiteralExpressionStatement,
-    kUseStrictExpressionStatement,
-    kUseAsmExpressionStatement,
   };
 
   explicit PreParserStatement(Type code) : code_(code) {}
@@ -1345,14 +1306,6 @@ class PreParser : public ParserBase<PreParser> {
     return false;
   }
 
-  V8_INLINE bool IsUseStrictDirective(PreParserStatement statement) const {
-    return statement.IsUseStrictLiteral();
-  }
-
-  V8_INLINE bool IsUseAsmDirective(PreParserStatement statement) const {
-    return statement.IsUseAsmLiteral();
-  }
-
   V8_INLINE bool IsStringLiteral(PreParserStatement statement) const {
     return statement.IsStringLiteral();
   }
@@ -1613,9 +1566,6 @@ class PreParser : public ParserBase<PreParser> {
   V8_INLINE PreParserExpression ExpressionFromLiteral(Token::Value token,
                                                       int pos) {
     if (token != Token::STRING) return PreParserExpression::Default();
-    if (scanner()->IsUseStrict()) {
-      return PreParserExpression::UseStrictStringLiteral();
-    }
     return PreParserExpression::StringLiteral();
   }
 

src/parsing/scanner.h

@@ -357,12 +357,6 @@ class Scanner {
                 Token::String(token), Token::StringLength(token))));
   }
 
-  bool IsUseStrict() const {
-    return current().token == Token::STRING &&
-           current().literal_chars.Equals(
-               Vector<const char>("use strict", strlen("use strict")));
-  }
-
   bool IsGet() { return CurrentMatchesContextual(Token::GET); }
 
   bool IsSet() { return CurrentMatchesContextual(Token::SET); }