Bug 1343481 - Part 2: Stop using StarGegerator for async function.

Tag #1287

4 files changed, 44 insertions, 39 deletions

diff --git a/js/src/frontend/BytecodeCompiler.cpp b/js/src/frontend/BytecodeCompiler.cpp
index a1abbfeda..7760c4b2e 100644
--- a/js/src/frontend/BytecodeCompiler.cpp
+++ b/js/src/frontend/BytecodeCompiler.cpp
@@ -727,5 +727,5 @@ frontend::CompileStandaloneAsyncFunction(JSContext* cx, MutableHandleFunction fu
 
     BytecodeCompiler compiler(cx, cx->tempLifoAlloc(), options, srcBuf, emptyGlobalScope,
                               TraceLogger_ParserCompileFunction);
-    return compiler.compileStandaloneFunction(fun, StarGenerator, AsyncFunction, parameterListEnd);
+    return compiler.compileStandaloneFunction(fun, NotGenerator, AsyncFunction, parameterListEnd);
 }
diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index 4dc4914dc..b8a9bdf7e 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -8443,7 +8443,8 @@ BytecodeEmitter::emitReturn(ParseNode* pn)
     if (!updateSourceCoordNotes(pn->pn_pos.begin))
         return false;
 
-    if (sc->isFunctionBox() && sc->asFunctionBox()->isStarGenerator()) {
+    bool needsIteratorResult = sc->isFunctionBox() && sc->asFunctionBox()->needsIteratorResult();
+    if (needsIteratorResult) {
         if (!emitPrepareIteratorResult())
             return false;
     }
@@ -8458,7 +8459,7 @@ BytecodeEmitter::emitReturn(ParseNode* pn)
             return false;
     }
 
-    if (sc->isFunctionBox() && sc->asFunctionBox()->isStarGenerator()) {
+    if (needsIteratorResult) {
         if (!emitFinishIteratorResult(true))
             return false;
     }
@@ -8530,7 +8531,8 @@ BytecodeEmitter::emitYield(ParseNode* pn)
     MOZ_ASSERT(sc->isFunctionBox());
 
     if (pn->getOp() == JSOP_YIELD) {
-        if (sc->asFunctionBox()->isStarGenerator()) {
+        bool needsIteratorResult = sc->asFunctionBox()->needsIteratorResult();
+        if (needsIteratorResult) {
             if (!emitPrepareIteratorResult())
                 return false;
         }
@@ -8541,7 +8543,7 @@ BytecodeEmitter::emitYield(ParseNode* pn)
             if (!emit1(JSOP_UNDEFINED))
                 return false;
         }
-        if (sc->asFunctionBox()->isStarGenerator()) {
+        if (needsIteratorResult) {
             if (!emitFinishIteratorResult(false))
                 return false;
         }
@@ -10319,14 +10321,19 @@ BytecodeEmitter::emitFunctionBody(ParseNode* funBody)
 
     if (funbox->needsFinalYield()) {
         // If we fall off the end of a generator, do a final yield.
-        if (funbox->isStarGenerator() && !emitPrepareIteratorResult())
-            return false;
+        bool needsIteratorResult = funbox->needsIteratorResult();
+        if (needsIteratorResult) {
+            if (!emitPrepareIteratorResult())
+                return false;
+        }
 
         if (!emit1(JSOP_UNDEFINED))
             return false;
 
-        if (funbox->isStarGenerator() && !emitFinishIteratorResult(true))
-            return false;
+        if (needsIteratorResult) {
+            if (!emitFinishIteratorResult(true))
+                return false;
+        }
 
         if (!emit1(JSOP_SETRVAL))
             return false;
diff --git a/js/src/frontend/Parser.cpp b/js/src/frontend/Parser.cpp
index 64b1f22c2..406d37725 100644
--- a/js/src/frontend/Parser.cpp
+++ b/js/src/frontend/Parser.cpp
@@ -2474,10 +2474,8 @@ Parser<SyntaxParseHandler>::finishFunction(bool isStandaloneFunction /* = false
 }
 
 static YieldHandling
-GetYieldHandling(GeneratorKind generatorKind, FunctionAsyncKind asyncKind)
+GetYieldHandling(GeneratorKind generatorKind)
 {
-    if (asyncKind == AsyncFunction)
-        return YieldIsName;
     if (generatorKind == NotGenerator)
         return YieldIsName;
     return YieldIsKeyword;
@@ -2541,7 +2539,7 @@ Parser<FullParseHandler>::standaloneFunction(HandleFunction fun,
         return null();
     funpc.setIsStandaloneFunctionBody();
 
-    YieldHandling yieldHandling = GetYieldHandling(generatorKind, asyncKind);
+    YieldHandling yieldHandling = GetYieldHandling(generatorKind);
     AutoAwaitIsKeyword<FullParseHandler> awaitIsKeyword(this, asyncKind == AsyncFunction);
     if (!functionFormalParametersAndBody(InAllowed, yieldHandling, fn, Statement,
                                          parameterListEnd, /* isStandaloneFunction = */ true))
@@ -2699,7 +2697,7 @@ Parser<ParseHandler>::functionBody(InHandling inHandling, YieldHandling yieldHan
 
     switch (pc->generatorKind()) {
       case NotGenerator:
-        MOZ_ASSERT(pc->lastYieldOffset == startYieldOffset);
+        MOZ_ASSERT_IF(!pc->isAsync(), pc->lastYieldOffset == startYieldOffset);
         break;
 
       case LegacyGenerator:
@@ -2715,8 +2713,8 @@ Parser<ParseHandler>::functionBody(InHandling inHandling, YieldHandling yieldHan
         break;
 
       case StarGenerator:
-        MOZ_ASSERT_IF(!pc->isAsync(), kind != Arrow);
-        MOZ_ASSERT_IF(!pc->isAsync(), type == StatementListBody);
+        MOZ_ASSERT(kind != Arrow);
+        MOZ_ASSERT(type == StatementListBody);
         break;
     }
 
@@ -2761,9 +2759,9 @@ Parser<ParseHandler>::newFunction(HandleAtom atom, FunctionSyntaxKind kind,
 #endif
     switch (kind) {
       case Expression:
-        flags = (generatorKind == NotGenerator
+        flags = (generatorKind == NotGenerator && asyncKind == SyncFunction
                  ? JSFunction::INTERPRETED_LAMBDA
-                 : JSFunction::INTERPRETED_LAMBDA_GENERATOR);
+                 : JSFunction::INTERPRETED_LAMBDA_GENERATOR_OR_ASYNC);
         break;
       case Arrow:
         flags = JSFunction::INTERPRETED_LAMBDA_ARROW;
@@ -2771,9 +2769,9 @@ Parser<ParseHandler>::newFunction(HandleAtom atom, FunctionSyntaxKind kind,
         break;
       case Method:
         MOZ_ASSERT(generatorKind == NotGenerator || generatorKind == StarGenerator);
-        flags = (generatorKind == NotGenerator
+        flags = (generatorKind == NotGenerator && asyncKind == SyncFunction
                  ? JSFunction::INTERPRETED_METHOD
-                 : JSFunction::INTERPRETED_METHOD_GENERATOR);
+                 : JSFunction::INTERPRETED_METHOD_GENERATOR_OR_ASYNC);
         allocKind = gc::AllocKind::FUNCTION_EXTENDED;
         break;
       case ClassConstructor:
@@ -2799,9 +2797,9 @@ Parser<ParseHandler>::newFunction(HandleAtom atom, FunctionSyntaxKind kind,
             allocKind = gc::AllocKind::FUNCTION_EXTENDED;
         }
 #endif
-        flags = (generatorKind == NotGenerator
+        flags = (generatorKind == NotGenerator && asyncKind == SyncFunction
                  ? JSFunction::INTERPRETED_NORMAL
-                 : JSFunction::INTERPRETED_GENERATOR);
+                 : JSFunction::INTERPRETED_GENERATOR_OR_ASYNC);
     }
 
     // We store the async wrapper in a slot for later access.
@@ -3324,7 +3322,6 @@ Parser<ParseHandler>::functionDefinition(uint32_t toStringStart, Node pn, InHand
                                          bool tryAnnexB /* = false */)
 {
     MOZ_ASSERT_IF(kind == Statement, funName);
-    MOZ_ASSERT_IF(asyncKind == AsyncFunction, generatorKind == StarGenerator);
 
     // When fully parsing a LazyScript, we do not fully reparse its inner
     // functions, which are also lazy. Instead, their free variables and
@@ -3336,7 +3333,7 @@ Parser<ParseHandler>::functionDefinition(uint32_t toStringStart, Node pn, InHand
     }
 
     RootedObject proto(context);
-    if (generatorKind == StarGenerator) {
+    if (generatorKind == StarGenerator || asyncKind == AsyncFunction) {
         // If we are off the main thread, the generator meta-objects have
         // already been created by js::StartOffThreadParseScript, so cx will not
         // be necessary.
@@ -3408,7 +3405,7 @@ Parser<FullParseHandler>::trySyntaxParseInnerFunction(ParseNode* pn, HandleFunct
         // parse to avoid the overhead of a lazy syntax-only parse. Although
         // the prediction may be incorrect, IIFEs are common enough that it
         // pays off for lots of code.
-        if (pn->isLikelyIIFE() && generatorKind == NotGenerator)
+        if (pn->isLikelyIIFE() && generatorKind == NotGenerator && asyncKind == SyncFunction)
             break;
 
         Parser<SyntaxParseHandler>* parser = handler.syntaxParser;
@@ -3584,7 +3581,7 @@ Parser<FullParseHandler>::standaloneLazyFunction(HandleFunction fun, bool strict
     if (!tokenStream.peekTokenPos(&pn->pn_pos, modifier))
         return null();
 
-    YieldHandling yieldHandling = GetYieldHandling(generatorKind, asyncKind);
+    YieldHandling yieldHandling = GetYieldHandling(generatorKind);
     FunctionSyntaxKind syntaxKind = Statement;
     if (fun->isClassConstructor())
         syntaxKind = ClassConstructor;
@@ -3665,7 +3662,7 @@ Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
         return false;
     uint32_t openedPos = 0;
     if (tt != TOK_LC) {
-        if ((funbox->isStarGenerator() && !funbox->isAsync()) || kind == Method ||
+        if (funbox->isStarGenerator() || kind == Method ||
             kind == GetterNoExpressionClosure || kind == SetterNoExpressionClosure ||
             IsConstructorKind(kind)) {
             error(JSMSG_CURLY_BEFORE_BODY);
@@ -3695,7 +3692,7 @@ Parser<ParseHandler>::functionFormalParametersAndBody(InHandling inHandling,
     // whether the arrow function is enclosed in a generator function or not.
     // Whereas the |yield| in the function body is always parsed as a name.
     // The same goes when parsing |await| in arrow functions.
-    YieldHandling bodyYieldHandling = GetYieldHandling(pc->generatorKind(), pc->asyncKind());
+    YieldHandling bodyYieldHandling = GetYieldHandling(pc->generatorKind());
     Node body;
     {
         AutoAwaitIsKeyword<ParseHandler> awaitIsKeyword(this, funbox->isAsync());
@@ -3786,7 +3783,7 @@ Parser<ParseHandler>::functionStmt(uint32_t toStringStart, YieldHandling yieldHa
     if (!tokenStream.getToken(&tt))
         return null();
 
-    GeneratorKind generatorKind = asyncKind == AsyncFunction ? StarGenerator : NotGenerator;
+    GeneratorKind generatorKind = NotGenerator;
     if (tt == TOK_MUL) {
         if (asyncKind != SyncFunction) {
             error(JSMSG_ASYNC_GENERATOR);
@@ -3817,7 +3814,7 @@ Parser<ParseHandler>::functionStmt(uint32_t toStringStart, YieldHandling yieldHa
         MOZ_ASSERT(declaredInStmt->kind() != StatementKind::Label);
         MOZ_ASSERT(StatementKindIsBraced(declaredInStmt->kind()));
 
-        if (!pc->sc()->strict() && generatorKind == NotGenerator) {
+        if (!pc->sc()->strict() && generatorKind == NotGenerator && asyncKind == SyncFunction) {
             // In sloppy mode, try Annex B.3.3 semantics. If making an
             // additional 'var' binding of the same name does not throw an
             // early error, do so. This 'var' binding would be assigned
@@ -3841,7 +3838,7 @@ Parser<ParseHandler>::functionStmt(uint32_t toStringStart, YieldHandling yieldHa
     if (!pn)
         return null();
 
-    YieldHandling newYieldHandling = GetYieldHandling(generatorKind, asyncKind);
+    YieldHandling newYieldHandling = GetYieldHandling(generatorKind);
     return functionDefinition(toStringStart, pn, InAllowed, newYieldHandling,
                                   name, Statement, generatorKind, asyncKind, tryAnnexB);
 }
@@ -3854,7 +3851,7 @@ Parser<ParseHandler>::functionExpr(uint32_t toStringStart, InvokedPrediction inv
     MOZ_ASSERT(tokenStream.isCurrentTokenType(TOK_FUNCTION));
 
     AutoAwaitIsKeyword<ParseHandler> awaitIsKeyword(this, asyncKind == AsyncFunction);
-    GeneratorKind generatorKind = asyncKind == AsyncFunction ? StarGenerator : NotGenerator;
+    GeneratorKind generatorKind = NotGenerator;
     TokenKind tt;
     if (!tokenStream.getToken(&tt))
         return null();
@@ -3869,7 +3866,7 @@ Parser<ParseHandler>::functionExpr(uint32_t toStringStart, InvokedPrediction inv
             return null();
     }
 
-    YieldHandling yieldHandling = GetYieldHandling(generatorKind, asyncKind);
+    YieldHandling yieldHandling = GetYieldHandling(generatorKind);
 
     RootedPropertyName name(context);
     if (TokenKindIsPossibleIdentifier(tt)) {
@@ -8187,7 +8184,6 @@ Parser<ParseHandler>::assignExpr(InHandling inHandling, YieldHandling yieldHandl
         uint32_t toStringStart = pos().begin;
         tokenStream.ungetToken();
 
-        GeneratorKind generatorKind = NotGenerator;
         FunctionAsyncKind asyncKind = SyncFunction;
 
         if (next == TOK_ASYNC) {
@@ -8200,7 +8196,6 @@ Parser<ParseHandler>::assignExpr(InHandling inHandling, YieldHandling yieldHandl
             if (nextSameLine == TOK_ARROW) {
                 tokenStream.ungetToken();
             } else {
-                generatorKind = StarGenerator;
                 asyncKind = AsyncFunction;
             }
         }
@@ -8210,7 +8205,7 @@ Parser<ParseHandler>::assignExpr(InHandling inHandling, YieldHandling yieldHandl
             return null();
 
         Node arrowFunc = functionDefinition(toStringStart, pn, inHandling, yieldHandling, nullptr,
-                                            Arrow, generatorKind, asyncKind);
+                                            Arrow, NotGenerator, asyncKind);
         if (!arrowFunc)
             return null();
 
@@ -9950,8 +9945,7 @@ Parser<ParseHandler>::methodDefinition(uint32_t toStringStart, PropertyType prop
         MOZ_CRASH("Parser: methodDefinition: unexpected property type");
     }
 
-    GeneratorKind generatorKind = (propType == PropertyType::GeneratorMethod ||
-                                   propType == PropertyType::AsyncMethod)
+    GeneratorKind generatorKind = propType == PropertyType::GeneratorMethod
                                   ? StarGenerator
                                   : NotGenerator;
 
@@ -9959,7 +9953,7 @@ Parser<ParseHandler>::methodDefinition(uint32_t toStringStart, PropertyType prop
                                   ? AsyncFunction
                                   : SyncFunction;
 
-    YieldHandling yieldHandling = GetYieldHandling(generatorKind, asyncKind);
+    YieldHandling yieldHandling = GetYieldHandling(generatorKind);
 
     Node pn = handler.newFunctionExpression();
     if (!pn)
diff --git a/js/src/frontend/SharedContext.h b/js/src/frontend/SharedContext.h
index 5766c135a..2d478308e 100644
--- a/js/src/frontend/SharedContext.h
+++ b/js/src/frontend/SharedContext.h
@@ -552,6 +552,10 @@ class FunctionBox : public ObjectBox, public SharedContext
         return isStarGenerator() || isLegacyGenerator() || isAsync();
     }
 
+    bool needsIteratorResult() const {
+        return isStarGenerator() || isAsync();
+    }
+
     bool isAsync() const { return asyncKind() == AsyncFunction; }
     bool isArrow() const { return function()->isArrow(); }