From d0d9a4f43dbd58c694c706b17996157fede20bdf Mon Sep 17 00:00:00 2001
From: Gaming4JC <g4jc@hyperbola.info>
Date: Fri, 13 Dec 2019 20:59:32 -0500
Subject: Bug 1316098 - Optimize out result object allocation for await/return
 in async function.

Tag #1287
---
 js/src/vm/AsyncFunction.cpp | 24 +++++-------------------
 js/src/vm/AsyncFunction.h   |  3 ---
 js/src/vm/Debugger.cpp      | 12 +++---------
 js/src/vm/Opcodes.h         |  6 +++---
 4 files changed, 11 insertions(+), 34 deletions(-)

(limited to 'js/src/vm')

diff --git a/js/src/vm/AsyncFunction.cpp b/js/src/vm/AsyncFunction.cpp
index be7a36ecc..2bcec5465 100644
--- a/js/src/vm/AsyncFunction.cpp
+++ b/js/src/vm/AsyncFunction.cpp
@@ -171,22 +171,14 @@ AsyncFunctionResume(JSContext* cx, Handle<PromiseObject*> resultPromise, HandleV
                                  : cx->names().StarGeneratorThrow;
     FixedInvokeArgs<1> args(cx);
     args[0].set(valueOrReason);
-    RootedValue result(cx);
-    if (!CallSelfHostedFunction(cx, funName, generatorVal, args, &result))
-        return AsyncFunctionThrown(cx, resultPromise);
-
-    RootedObject resultObj(cx, &result.toObject());
-    RootedValue doneVal(cx);
     RootedValue value(cx);
-    if (!GetProperty(cx, resultObj, resultObj, cx->names().done, &doneVal))
-        return false;
-    if (!GetProperty(cx, resultObj, resultObj, cx->names().value, &value))
-        return false;
+    if (!CallSelfHostedFunction(cx, funName, generatorVal, args, &value))
+        return AsyncFunctionThrown(cx, resultPromise);
 
-    if (doneVal.toBoolean())
-        return AsyncFunctionReturned(cx, resultPromise, value);
+    if (generatorVal.toObject().as<GeneratorObject>().isAfterAwait())
+        return AsyncFunctionAwait(cx, resultPromise, value);
 
-    return AsyncFunctionAwait(cx, resultPromise, value);
+    return AsyncFunctionReturned(cx, resultPromise, value);
 }
 
 // Async Functions proposal 2.2 steps 3-8.
@@ -242,9 +234,3 @@ js::IsWrappedAsyncFunction(JSFunction* fun)
 {
     return fun->maybeNative() == WrappedAsyncFunction;
 }
-
-MOZ_MUST_USE bool
-js::CheckAsyncResumptionValue(JSContext* cx, HandleValue v)
-{
-    return CheckStarGeneratorResumptionValue(cx, v);
-}
diff --git a/js/src/vm/AsyncFunction.h b/js/src/vm/AsyncFunction.h
index d7f2c1311..de7c87d13 100644
--- a/js/src/vm/AsyncFunction.h
+++ b/js/src/vm/AsyncFunction.h
@@ -35,9 +35,6 @@ MOZ_MUST_USE bool
 AsyncFunctionAwaitedRejected(JSContext* cx, Handle<PromiseObject*> resultPromise,
                              HandleValue generatorVal, HandleValue reason);
 
-MOZ_MUST_USE bool
-CheckAsyncResumptionValue(JSContext* cx, HandleValue v);
-
 } // namespace js
 
 #endif /* vm_AsyncFunction_h */
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index 7c09c50b0..2680699a4 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -32,7 +32,6 @@
 #include "js/Vector.h"
 #include "proxy/ScriptedProxyHandler.h"
 #include "vm/ArgumentsObject.h"
-#include "vm/AsyncFunction.h"
 #include "vm/DebuggerMemory.h"
 #include "vm/GeneratorObject.h"
 #include "vm/SPSProfiler.h"
@@ -1560,16 +1559,11 @@ CheckResumptionValue(JSContext* cx, AbstractFramePtr frame, const Maybe<HandleVa
                      JSTrapStatus status, MutableHandleValue vp)
 {
     if (status == JSTRAP_RETURN && frame && frame.isFunctionFrame()) {
-        // Don't let a { return: ... } resumption value make a generator or
-        // async function violate the iterator protocol. The return value from
+        // Don't let a { return: ... } resumption value make a generator
+        // function violate the iterator protocol. The return value from
         // such a frame must have the form { done: <bool>, value: <anything> }.
         RootedFunction callee(cx, frame.callee());
-        if (callee->isAsync()) {
-            if (!CheckAsyncResumptionValue(cx, vp)) {
-                JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_DEBUG_BAD_AWAIT);
-                return false;
-            }
-        } else if (callee->isStarGenerator() || callee->isAsync()) {
+        if (callee->isStarGenerator()) {
             if (!CheckStarGeneratorResumptionValue(cx, vp)) {
                 JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_DEBUG_BAD_YIELD);
                 return false;
diff --git a/js/src/vm/Opcodes.h b/js/src/vm/Opcodes.h
index b44628080..583d32beb 100644
--- a/js/src/vm/Opcodes.h
+++ b/js/src/vm/Opcodes.h
@@ -2120,12 +2120,12 @@
      */ \
     macro(JSOP_DEBUGAFTERYIELD,  208, "debugafteryield",  NULL,  1,  0,  0,  JOF_BYTE) \
     /*
-     * Pops the generator and the return value 'result', stops interpretation
-     * and returns 'result'. Pushes resolved value onto the stack.
+     * Pops the generator and the return value 'promise', stops interpretation
+     * and returns 'promise'. Pushes resolved value onto the stack.
      *   Category: Statements
      *   Type: Generator
      *   Operands: uint24_t yieldAndAwaitIndex
-     *   Stack: result, gen => resolved
+     *   Stack: promise, gen => resolved
      */ \
     macro(JSOP_AWAIT,         209, "await",        NULL,  4,  2,  1,  JOF_UINT24) \
     macro(JSOP_UNUSED210,     210, "unused210",    NULL,  1,  0,  0,  JOF_BYTE) \
-- 
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