Bug 1674465 - Add CompileOptions::useStencilXDR. r=arai

No changes to behaviour. This splits the useOffThreadParseGlobal flag into
cases that care about the format and cases that care about the GC.

Depends on D95380

Differential Revision: https://phabricator.services.mozilla.com/D95381

js/public/CompileOptions.h

@@ -133,6 +133,9 @@ class JS_PUBLIC_API TransitiveCompileOptions {
   bool privateClassFields = false;
   bool privateClassMethods = false;
 
+  // True if transcoding to XDR should use Stencil instead of JSScripts.
+  bool useStencilXDR = false;
+
   // True if off-thread parsing should use a parse GlobalObject in order to
   // directly allocate to the GC from a helper thread. If false, transfer the
   // CompilationStencil back to main thread before allocating GC objects.

js/src/jsapi.cpp

@@ -3461,6 +3461,7 @@ void JS::TransitiveCompileOptions::copyPODTransitiveOptions(
   nonSyntacticScope = rhs.nonSyntacticScope;
   privateClassFields = rhs.privateClassFields;
   privateClassMethods = rhs.privateClassMethods;
+  useStencilXDR = rhs.useStencilXDR;
   useOffThreadParseGlobal = rhs.useOffThreadParseGlobal;
 };
 
@@ -3555,6 +3556,8 @@ JS::CompileOptions::CompileOptions(JSContext* cx)
       cx->options().throwOnAsmJSValidationFailure();
   privateClassFields = cx->options().privateClassFields();
   privateClassMethods = cx->options().privateClassMethods();
+
+  useStencilXDR = !UseOffThreadParseGlobal();
   useOffThreadParseGlobal = UseOffThreadParseGlobal();
 
   sourcePragmas_ = cx->options().sourcePragmas();
@@ -5752,8 +5755,7 @@ JS_PUBLIC_API JS::TranscodeResult JS::DecodeScriptMaybeStencil(
     JSContext* cx, const ReadOnlyCompileOptions& options,
     TranscodeBuffer& buffer, JS::MutableHandleScript scriptp,
     size_t cursorIndex) {
-  bool useStencilXDR = !options.useOffThreadParseGlobal;
-  if (!useStencilXDR) {
+  if (!options.useStencilXDR) {
     // The buffer contains JSScript.
     return JS::DecodeScript(cx, options, buffer, scriptp, cursorIndex);
   }
@@ -5802,8 +5804,7 @@ JS_PUBLIC_API JS::TranscodeResult JS::DecodeScriptAndStartIncrementalEncoding(
     JSContext* cx, const ReadOnlyCompileOptions& options,
     TranscodeBuffer& buffer, JS::MutableHandleScript scriptp,
     size_t cursorIndex) {
-  bool useStencilXDR = !options.useOffThreadParseGlobal;
-  if (!useStencilXDR) {
+  if (!options.useStencilXDR) {
     JS::TranscodeResult res =
         JS::DecodeScript(cx, options, buffer, scriptp, cursorIndex);
     if (res != JS::TranscodeResult_Ok) {

js/src/shell/js.cpp

@@ -2440,10 +2440,10 @@ static bool Evaluate(JSContext* cx, unsigned argc, Value* vp) {
       if (!FinishIncrementalEncoding(cx, script, saveBuffer)) {
         return false;
       }
-      if (js::UseOffThreadParseGlobal()) {
-        saveCacheKind = BytecodeCacheKind::Script;
-      } else {
+      if (options.useStencilXDR) {
         saveCacheKind = BytecodeCacheKind::Stencil;
+      } else {
+        saveCacheKind = BytecodeCacheKind::Script;
       }
     }
   }
@@ -5917,6 +5917,8 @@ static bool OffThreadDecodeScript(JSContext* cx, unsigned argc, Value* vp) {
   // for saveBytecode, or stencil for saveIncrementalBytecode.
   options.useOffThreadParseGlobal =
       CacheEntry_getKind(cx, cacheEntry) == BytecodeCacheKind::Script;
+  options.useStencilXDR =
+      CacheEntry_getKind(cx, cacheEntry) == BytecodeCacheKind::Stencil;
 
   if (args.length() >= 2) {
     if (args[1].isPrimitive()) {

js/src/vm/CompilationAndEvaluation.cpp

@@ -112,8 +112,7 @@ static JSScript* CompileSourceBufferAndStartIncrementalEncoding(
     return nullptr;
   }
 
-  bool useStencilXDR = !options.useOffThreadParseGlobal;
-  if (useStencilXDR) {
+  if (options.useStencilXDR) {
     UniquePtr<XDRIncrementalEncoderBase> xdrEncoder;
 
     if (!compilationInfo.get().input.source()->xdrEncodeInitialStencil(

js/src/vm/HelperThreads.cpp

@@ -778,8 +778,7 @@ void ScriptDecodeTask::parse(JSContext* cx) {
   RootedScript resultScript(cx);
   Rooted<ScriptSourceObject*> sourceObject(cx);
 
-  bool useStencilXDR = !options.useOffThreadParseGlobal;
-  if (useStencilXDR) {
+  if (options.useStencilXDR) {
     // The buffer contains stencil.
     Rooted<UniquePtr<frontend::CompilationInfoVector>> compilationInfos(
         cx, js_new<frontend::CompilationInfoVector>(cx, options));
@@ -1218,6 +1217,9 @@ bool js::StartOffThreadDecodeScript(JSContext* cx,
     return false;
   }
 
+  // XDR data must be Stencil format, or a parse-global must be available.
+  MOZ_RELEASE_ASSERT(options.useStencilXDR || options.useOffThreadParseGlobal);
+
   return StartOffThreadParseTask(cx, std::move(task), options);
 }
 
@@ -1237,6 +1239,7 @@ bool js::StartOffThreadDecodeMultiScripts(JSContext* cx,
   //       they must continue to use the off-thread-parse-global in order to
   //       decode.
   CompileOptions optionsCopy(cx, options);
+  optionsCopy.useStencilXDR = false;
   optionsCopy.useOffThreadParseGlobal = true;
 
   return StartOffThreadParseTask(cx, std::move(task), optionsCopy);
@@ -2114,8 +2117,7 @@ JSScript* GlobalHelperThreadState::finishSingleParseTask(
 
   // Start the incremental-XDR encoder.
   if (startEncoding == StartEncoding::Yes) {
-    bool useStencilXDR = !parseTask->options.useOffThreadParseGlobal;
-    if (useStencilXDR) {
+    if (parseTask->options.useStencilXDR) {
       UniquePtr<XDRIncrementalEncoderBase> xdrEncoder;
 
       if (parseTask->compilationInfo_.get()) {

js/src/vm/JSFunction.cpp

@@ -1609,6 +1609,8 @@ bool DelazifyCanonicalScriptedFunctionImpl(JSContext* cx, HandleFunction fun,
     }
 
     if (ss->hasEncoder()) {
+      // NOTE: Currently we rely on the UseOffThreadParseGlobal to decide which
+      //       format to use for incremental encoding.
       bool useStencilXDR = !js::UseOffThreadParseGlobal();
       if (useStencilXDR) {
         if (!ss->xdrEncodeFunctionStencil(cx, compilationInfo.get().stencil)) {