Add UseCounter for decimal with leading zero.

Re-landing https://codereview.chromium.org/1948403002/

New changes:

move variable initialization to make compiler happy

BUG=v8:4973
LOG=y

Review-Url: https://codereview.chromium.org/1969203004
Cr-Commit-Position: refs/heads/master@{#36262}

include/v8.h

@@ -5635,9 +5635,10 @@ class V8_EXPORT Isolate {
     kLegacyFunctionDeclaration = 29,
     kRegExpPrototypeSourceGetter = 30,
     kRegExpPrototypeOldFlagGetter = 31,
+    kDecimalWithLeadingZeroInStrictMode = 32,
 
-    // If you add new values here, you'll also need to update V8Initializer.cpp
+    // If you add new values here, you'll also need to update Chromium's:
-    // in Chromium.
+    // UseCounter.h, V8PerIsolateData.cpp, histograms.xml
     kUseCounterFeatureCount  // This enum value must be last.
   };
 

src/parsing/parser-base.h

@@ -718,6 +718,18 @@ class ParserBase : public Traits {
       *ok = false;
     }
   }
+  // for now, this check just collects statistics.
+  void CheckDecimalLiteralWithLeadingZero(int* use_counts, int beg_pos,
+                                          int end_pos) {
+    Scanner::Location token_location =
+        scanner()->decimal_with_leading_zero_position();
+    if (token_location.IsValid() && beg_pos <= token_location.beg_pos &&
+        token_location.end_pos <= end_pos) {
+      scanner()->clear_decimal_with_leading_zero_position();
+      if (use_counts != nullptr)
+        ++use_counts[v8::Isolate::kDecimalWithLeadingZeroInStrictMode];
+    }
+  }
 
   inline void CheckStrictOctalLiteral(int beg_pos, int end_pos, bool* ok) {
     CheckOctalLiteral(beg_pos, end_pos, MessageTemplate::kStrictOctalLiteral,

src/parsing/parser.cc

@@ -949,6 +949,8 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
 
     if (ok && is_strict(language_mode())) {
       CheckStrictOctalLiteral(beg_pos, scanner()->location().end_pos, &ok);
+      CheckDecimalLiteralWithLeadingZero(use_counts_, beg_pos,
+                                         scanner()->location().end_pos);
     }
     if (ok && is_sloppy(language_mode())) {
       // TODO(littledan): Function bindings on the global object that modify
@@ -4261,6 +4263,8 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
     if (is_strict(language_mode)) {
       CheckStrictOctalLiteral(scope->start_position(), scope->end_position(),
                               CHECK_OK);
+      CheckDecimalLiteralWithLeadingZero(use_counts_, scope->start_position(),
+                                         scope->end_position());
     }
     if (is_sloppy(language_mode)) {
       InsertSloppyBlockFunctionVarBindings(scope, CHECK_OK);

src/parsing/preparser.cc

@@ -136,6 +136,7 @@ PreParser::PreParseResult PreParser::PreParseLazyFunction(
     if (is_strict(scope_->language_mode())) {
       int end_pos = scanner()->location().end_pos;
       CheckStrictOctalLiteral(start_position, end_pos, &ok);
+      CheckDecimalLiteralWithLeadingZero(use_counts, start_position, end_pos);
       if (!ok) return kPreParseSuccess;
     }
   }
@@ -1143,6 +1144,8 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
   if (is_strict(language_mode)) {
     int end_position = scanner()->location().end_pos;
     CheckStrictOctalLiteral(start_position, end_position, CHECK_OK);
+    CheckDecimalLiteralWithLeadingZero(use_counts_, start_position,
+                                       end_position);
   }
 
   return Expression::Default();

src/parsing/preparser.h

@@ -1054,6 +1054,8 @@ class PreParser : public ParserBase<PreParserTraits> {
     } else if (is_strict(scope_->language_mode())) {
       CheckStrictOctalLiteral(start_position, scanner()->location().end_pos,
                               &ok);
+      CheckDecimalLiteralWithLeadingZero(use_counts_, start_position,
+                                         scanner()->location().end_pos);
     }
     if (materialized_literals) {
       *materialized_literals = function_state_->materialized_literal_count();

src/parsing/scanner.cc

@@ -40,6 +40,7 @@ Scanner::Scanner(UnicodeCache* unicode_cache)
     : unicode_cache_(unicode_cache),
       bookmark_c0_(kNoBookmark),
       octal_pos_(Location::invalid()),
+      decimal_with_leading_zero_pos_(Location::invalid()),
       found_html_comment_(false),
       allow_harmony_exponentiation_operator_(false) {
   bookmark_current_.literal_chars = &bookmark_current_literal_;
@@ -981,10 +982,18 @@ void Scanner::ScanDecimalDigits() {
 Token::Value Scanner::ScanNumber(bool seen_period) {
   DCHECK(IsDecimalDigit(c0_));  // the first digit of the number or the fraction
 
-  enum { DECIMAL, HEX, OCTAL, IMPLICIT_OCTAL, BINARY } kind = DECIMAL;
+  enum {
+    DECIMAL,
+    DECIMAL_WITH_LEADING_ZERO,
+    HEX,
+    OCTAL,
+    IMPLICIT_OCTAL,
+    BINARY
+  } kind = DECIMAL;
 
   LiteralScope literal(this);
   bool at_start = !seen_period;
+  int start_pos = source_pos();  // For reporting octal positions.
   if (seen_period) {
     // we have already seen a decimal point of the float
     AddLiteralChar('.');
@@ -993,7 +1002,6 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
   } else {
     // if the first character is '0' we must check for octals and hex
     if (c0_ == '0') {
-      int start_pos = source_pos();  // For reporting octal positions.
       AddLiteralCharAdvance();
 
       // either 0, 0exxx, 0Exxx, 0.xxx, a hex number, a binary number or
@@ -1035,7 +1043,7 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
         while (true) {
           if (c0_ == '8' || c0_ == '9') {
             at_start = false;
-            kind = DECIMAL;
+            kind = DECIMAL_WITH_LEADING_ZERO;
             break;
           }
           if (c0_  < '0' || '7'  < c0_) {
@@ -1045,11 +1053,13 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
           }
           AddLiteralCharAdvance();
         }
+      } else if (c0_ == '8' || c0_ == '9') {
+        kind = DECIMAL_WITH_LEADING_ZERO;
       }
     }
 
     // Parse decimal digits and allow trailing fractional part.
-    if (kind == DECIMAL) {
+    if (kind == DECIMAL || kind == DECIMAL_WITH_LEADING_ZERO) {
       if (at_start) {
         uint64_t value = 0;
         while (IsDecimalDigit(c0_)) {
@@ -1066,6 +1076,8 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
           literal.Complete();
           HandleLeadSurrogate();
 
+          if (kind == DECIMAL_WITH_LEADING_ZERO)
+            decimal_with_leading_zero_pos_ = Location(start_pos, source_pos());
           return Token::SMI;
         }
         HandleLeadSurrogate();
@@ -1082,7 +1094,8 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
   // scan exponent, if any
   if (c0_ == 'e' || c0_ == 'E') {
     DCHECK(kind != HEX);  // 'e'/'E' must be scanned as part of the hex number
-    if (kind != DECIMAL) return Token::ILLEGAL;
+    if (!(kind == DECIMAL || kind == DECIMAL_WITH_LEADING_ZERO))
+      return Token::ILLEGAL;
     // scan exponent
     AddLiteralCharAdvance();
     if (c0_ == '+' || c0_ == '-')
@@ -1104,6 +1117,8 @@ Token::Value Scanner::ScanNumber(bool seen_period) {
 
   literal.Complete();
 
+  if (kind == DECIMAL_WITH_LEADING_ZERO)
+    decimal_with_leading_zero_pos_ = Location(start_pos, source_pos());
   return Token::NUMBER;
 }
 

src/parsing/scanner.h

@@ -425,6 +425,13 @@ class Scanner {
   // Returns the location of the last seen octal literal.
   Location octal_position() const { return octal_pos_; }
   void clear_octal_position() { octal_pos_ = Location::invalid(); }
+  // Returns the location of the last seen decimal literal with a leading zero.
+  Location decimal_with_leading_zero_position() const {
+    return decimal_with_leading_zero_pos_;
+  }
+  void clear_decimal_with_leading_zero_position() {
+    decimal_with_leading_zero_pos_ = Location::invalid();
+  }
 
   // Returns the value of the last smi that was scanned.
   int smi_value() const { return current_.smi_value_; }
@@ -778,9 +785,9 @@ class Scanner {
   // Input stream. Must be initialized to an Utf16CharacterStream.
   Utf16CharacterStream* source_;
 
-
+  // Last-seen positions of potentially problematic tokens.
-  // Start position of the octal literal last scanned.
   Location octal_pos_;
+  Location decimal_with_leading_zero_pos_;
 
   // One Unicode character look-ahead; c0_ < 0 at the end of the input.
   uc32 c0_;