Bug 1625212 - Give RegExpShared a cell header r=sfink

I had to reorder the fields here to make so the first field was simple to replace.

Differential Revision: https://phabricator.services.mozilla.com/D68837

--HG--
extra : moz-landing-system : lando

js/src/vm/RegExpObject.cpp

@@ -932,7 +932,10 @@ bool js::StringHasRegExpMetaChars(JSLinearString* str) {
 /* RegExpShared */
 
 RegExpShared::RegExpShared(JSAtom* source, RegExpFlags flags)
-    : source(source), parenCount(0), flags(flags), canStringMatch(false) {}
+    : headerAndSource(source),
+      parenCount(0),
+      flags(flags),
+      canStringMatch(false) {}
 
 void RegExpShared::traceChildren(JSTracer* trc) {
   // Discard code to avoid holding onto ExecutablePools.
@@ -940,7 +943,7 @@ void RegExpShared::traceChildren(JSTracer* trc) {
     discardJitCode();
   }
 
-  TraceNullableEdge(trc, &source, "RegExpShared source");
+  TraceNullableEdge(trc, &headerAndSource, "RegExpShared source");
   for (auto& comp : compilationArray) {
     TraceNullableEdge(trc, &comp.jitCode, "RegExpShared code");
   }
@@ -972,7 +975,7 @@ bool RegExpShared::compile(JSContext* cx, MutableHandleRegExpShared re,
   TraceLoggerThread* logger = TraceLoggerForCurrentThread(cx);
   AutoTraceLog logCompile(logger, TraceLogger_IrregexpCompile);
 
-  RootedAtom pattern(cx, re->source);
+  RootedAtom pattern(cx, re->getSource());
   return compile(cx, re, pattern, input, mode, force);
 }
 
@@ -1079,14 +1082,14 @@ RegExpRunStatus RegExpShared::execute(JSContext* cx,
 
   if (re->canStringMatch) {
     MOZ_ASSERT(re->pairCount() == 1);
-    size_t sourceLength = re->source->length();
+    size_t sourceLength = re->getSource()->length();
     if (re->sticky()) {
       // First part checks size_t overflow.
       if (sourceLength + start < sourceLength ||
           sourceLength + start > length) {
         return RegExpRunStatus_Success_NotFound;
       }
-      if (!HasSubstringAt(input, re->source, start)) {
+      if (!HasSubstringAt(input, re->getSource(), start)) {
         return RegExpRunStatus_Success_NotFound;
       }
 
@@ -1101,7 +1104,7 @@ RegExpRunStatus RegExpShared::execute(JSContext* cx,
       return RegExpRunStatus_Success;
     }
 
-    int res = StringFindPattern(input, re->source, start);
+    int res = StringFindPattern(input, re->getSource(), start);
     if (res == -1) {
       return RegExpRunStatus_Success_NotFound;
     }

js/src/vm/RegExpShared.h

@@ -97,10 +97,11 @@ class RegExpShared : public gc::TenuredCell {
     }
   };
 
-  RegExpCompilation compilationArray[4];
-
   /* Source to the RegExp, for lazy compilation. */
-  const GCPtrAtom source;
+  using HeaderWithAtom = gc::CellHeaderWithTenuredGCPointer<JSAtom>;
+  HeaderWithAtom headerAndSource;
+
+  RegExpCompilation compilationArray[4];
 
   uint32_t parenCount;
   JS::RegExpFlags flags;
@@ -164,7 +165,7 @@ class RegExpShared : public gc::TenuredCell {
   /* Accounts for the "0" (whole match) pair. */
   size_t pairCount() const { return getParenCount() + 1; }
 
-  JSAtom* getSource() const { return source; }
+  JSAtom* getSource() const { return headerAndSource.ptr(); }
   JS::RegExpFlags getFlags() const { return flags; }
 
   bool global() const { return flags.global(); }
@@ -187,7 +188,10 @@ class RegExpShared : public gc::TenuredCell {
   void discardJitCode();
   void finalize(JSFreeOp* fop);
 
-  static size_t offsetOfSource() { return offsetof(RegExpShared, source); }
+  static size_t offsetOfSource() {
+    return offsetof(RegExpShared, headerAndSource) +
+           HeaderWithAtom::offsetOfPtr();
+  }
 
   static size_t offsetOfFlags() { return offsetof(RegExpShared, flags); }
 
@@ -212,6 +216,10 @@ class RegExpShared : public gc::TenuredCell {
   static bool dumpBytecode(JSContext* cx, MutableHandleRegExpShared res,
                            bool match_only, HandleLinearString input);
 #endif
+
+ public:
+  static const JS::TraceKind TraceKind = JS::TraceKind::RegExpShared;
+  const gc::CellHeader& cellHeader() const { return headerAndSource; }
 };
 
 class RegExpZone {

js/src/vm/RegExpStatics.h

@@ -243,7 +243,7 @@ inline void RegExpStatics::updateLazily(JSContext* cx, JSLinearString* input,
   BarrieredSetPair<JSString, JSLinearString>(cx->zone(), pendingInput, input,
                                              matchesInput, input);
 
-  lazySource = shared->source;
+  lazySource = shared->getSource();
   lazyFlags = shared->flags;
   lazyIndex = lastIndex;
   pendingLazyEvaluation = 1;