Bug 827539 - Remove unnecessary SkipRoots in the frontend; r=billm

js/src/frontend/TokenStream.cpp

@@ -119,15 +119,12 @@ frontend::IsIdentifier(JSLinearString *str)
 TokenStream::TokenStream(JSContext *cx, const CompileOptions &options,
                          StableCharPtr base, size_t length, StrictModeGetter *smg)
   : tokens(),
-    tokensRoot(cx, &tokens),
     cursor(),
     lookahead(),
     lineno(options.lineno),
     flags(),
     linebase(base.get()),
     prevLinebase(NULL),
-    linebaseRoot(cx, &linebase),
-    prevLinebaseRoot(cx, &prevLinebase),
     userbuf(base.get(), length),
     filename(options.filename),
     sourceMap(NULL),
@@ -139,7 +136,8 @@ TokenStream::TokenStream(JSContext *cx, const CompileOptions &options,
     cx(cx),
     originPrincipals(JSScript::normalizeOriginPrincipals(options.principals,
                                                          options.originPrincipals)),
-    strictModeGetter(smg)
+    strictModeGetter(smg),
+    tokenSkip(cx, &tokens)
 {
     if (originPrincipals)
         JS_HoldPrincipals(originPrincipals);
@@ -1442,8 +1440,6 @@ TokenStream::getTokenInternal()
     const jschar *identStart;
     bool hadUnicodeEscape;
 
-    SkipRoot skipNum(cx, &numStart), skipIdent(cx, &identStart);
-
 #if JS_HAS_XML_SUPPORT
     /*
      * Look for XML text and tags.

js/src/frontend/TokenStream.h

@@ -852,15 +852,12 @@ class TokenStream
     void updateFlagsForEOL();
 
     Token               tokens[ntokens];/* circular token buffer */
-    js::SkipRoot        tokensRoot;     /* prevent overwriting of token buffer */
     unsigned            cursor;         /* index of last parsed token */
     unsigned            lookahead;      /* count of lookahead tokens */
     unsigned            lineno;         /* current line number */
     unsigned            flags;          /* flags -- see above */
     const jschar        *linebase;      /* start of current line;  points into userbuf */
     const jschar        *prevLinebase;  /* start of previous line;  NULL if on the first line */
-    js::SkipRoot        linebaseRoot;
-    js::SkipRoot        prevLinebaseRoot;
     TokenBuf            userbuf;        /* user input buffer */
     const char          *filename;      /* input filename or null */
     jschar              *sourceMap;     /* source map's filename or null */
@@ -876,6 +873,13 @@ class TokenStream
     JSPrincipals        *const originPrincipals;
     StrictModeGetter    *strictModeGetter; /* used to test for strict mode */
     Position            lastFunctionKeyword; /* used as a starting point for reparsing strict functions */
+
+    /*
+     * The tokens array stores pointers to JSAtoms. These are rooted by the
+     * atoms table using AutoKeepAtoms in the Parser. This SkipRoot tells the
+     * exact rooting analysis to ignore the atoms in the tokens array.
+     */
+    SkipRoot            tokenSkip;
 };
 
 struct KeywordInfo {