[1.9>master] [MERGE #4796 @mrkmarron] Fixes for step-back with async

Merge pull request #4796 from mrkmarron:asyncfixes19

Add missing snapshot visit location.
Fix previous line logic for inline awaits.

Author: mrkmarron

lib/Jsrt/Jsrt.cpp

@@ -4616,7 +4616,7 @@ CHAKRA_API JsTTDReplayExecution(_Inout_ JsTTDMoveMode* moveMode, _Out_ int64_t*
             *moveMode = (JsTTDMoveMode)abortException.GetMoveMode();
             *rootEventTime = abortException.GetTargetEventTime();
 
-            //Check if we are tracking execution and, if so, set the exception locaiton so we can access it later
+            //Check if we are tracking execution and, if so, set the exception location so we can access it later
             if(emanager != nullptr && abortException.IsTopLevelException())
             {
                 emanager->SetPendingTTDUnhandledException();

lib/Runtime/Debug/TTExecutionInfo.cpp

@@ -603,7 +603,7 @@ namespace TTD
             this->m_lastReturnLocation.SetExceptionLocation(this->m_callStack.Last());
         }
 
-        if(!m_lastExceptionPropagating)
+        if(!this->m_lastExceptionPropagating)
         {
             this->m_lastExceptionLocation.SetLocationFromFrame(this->m_topLevelCallbackEventTime, this->m_callStack.Last());
             this->m_lastExceptionPropagating = true;
@@ -893,10 +893,15 @@ namespace TTD
             {
                 int32 cIndex = fb->GetEnclosingStatementIndexFromByteCode(bytecodeOffset, true);
 
-                //we moved to a new statement
+                //We moved to a new statement
                 Js::FunctionBody::StatementMap* pstmt = fb->GetStatementMaps()->Item(cIndex);
                 bool newstmt = (cIndex != cfinfo.CurrentStatementIndex && pstmt->byteCodeSpan.begin <= (int)bytecodeOffset && (int)bytecodeOffset <= pstmt->byteCodeSpan.end);
-                if (newstmt)
+
+                //Make sure async step back is ok -- We always step back to the first location in a statement and in most cases a function body must start at the first location in a statement.
+                //However an await can be in the middle of a statment/expression and is implicitly the start of a function body. So, we must check for that case.
+                bool functionBodyStartUnalignedWithStatementCase = (cfinfo.CurrentStatementIndex == -1) && (pstmt->byteCodeSpan.begin != (int)bytecodeOffset);
+
+                if (newstmt && !functionBodyStartUnalignedWithStatementCase)
                 {
                     cfinfo.LastStatementIndex = cfinfo.CurrentStatementIndex;
                     cfinfo.LastStatementLoopTime = cfinfo.CurrentStatementLoopTime;
@@ -997,9 +1002,15 @@ namespace TTD
         {
             SingleCallCounter cfinfoCaller = { 0 };
             bool hasCaller = this->TryGetTopCallCallerCounter(cfinfoCaller);
+            if (hasCaller)
+            {
+                ftime = cfinfoCaller.FunctionTime;
+                ltime = cfinfoCaller.CurrentStatementLoopTime;
 
-            //check if we are at the first statement in the callback event
-            if(!hasCaller)
+                fbody = cfinfoCaller.Function;
+                statementIndex = cfinfoCaller.CurrentStatementIndex;
+            }
+            else
             {
                 //Set the position info to the current statement and return true
                 noPrevious = true;
@@ -1010,14 +1021,6 @@ namespace TTD
                 fbody = cfinfo.Function;
                 statementIndex = cfinfo.CurrentStatementIndex;
             }
-            else
-            {
-                ftime = cfinfoCaller.FunctionTime;
-                ltime = cfinfoCaller.CurrentStatementLoopTime;
-
-                fbody = cfinfoCaller.Function;
-                statementIndex = cfinfoCaller.CurrentStatementIndex;
-            }
         }
         else
         {
@@ -1041,6 +1044,7 @@ namespace TTD
     void ExecutionInfoManager::GetLastExecutedTimeAndPositionForDebugger(TTDebuggerSourceLocation& sourceLocation) const
     {
         const TTLastReturnLocationInfo& cframe = this->m_lastReturnLocation;
+
         if(!cframe.IsDefined())
         {
             sourceLocation.Clear();

lib/Runtime/Library/JavascriptGeneratorFunction.cpp

@@ -599,6 +599,13 @@ namespace Js
         }
     }
 
+    void GeneratorVirtualScriptFunction::MarkVisitKindSpecificPtrs(TTD::SnapshotExtractor* extractor)
+    {
+        this->ScriptFunction::MarkVisitKindSpecificPtrs(extractor);
+
+        extractor->MarkVisitVar(this->realFunction);
+    }
+
     TTD::NSSnapObjects::SnapObjectType GeneratorVirtualScriptFunction::GetSnapTag_TTD() const
     {
         return TTD::NSSnapObjects::SnapObjectType::SnapGeneratorVirtualScriptFunction;

lib/Runtime/Library/JavascriptGeneratorFunction.h

@@ -155,6 +155,7 @@ namespace Js
         void SetRealGeneratorFunction(JavascriptGeneratorFunction* realFunction) { this->realFunction = realFunction; }
 
 #if ENABLE_TTD
+        virtual void MarkVisitKindSpecificPtrs(TTD::SnapshotExtractor* extractor) override;
         virtual TTD::NSSnapObjects::SnapObjectType GetSnapTag_TTD() const override;
         virtual void ExtractSnapObjectDataInto(TTD::NSSnapObjects::SnapObject* objData, TTD::SlabAllocator& alloc) override;
 #endif

test/TTBasic/asyncAwait2.js

@@ -0,0 +1,23 @@
+//-------------------------------------------------------------------------------------------------------
+// Copyright (C) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.txt file in the project root for full license information.
+//-------------------------------------------------------------------------------------------------------
+
+function resolveWait(x) {
+    return new Promise(resolve => {
+        WScript.SetTimeout(() => {
+            resolve(x);
+        }, 100);
+    });
+}
+
+async function awaitImm(x) {
+    const a = await resolveWait(1);
+    const b = await resolveWait(2);
+    return x + a + b;
+}
+
+awaitImm(1).then(v => {
+    telemetryLog(v.toString(), true);
+    emitTTDLog(ttdLogURI);
+});

test/TTBasic/asyncAwait2Record.baseline

@@ -0,0 +1 @@
+4

test/TTBasic/asyncAwait2Replay_1.baseline

@@ -0,0 +1,3 @@
+4
+
+Reached end of Execution -- Exiting.

test/TTBasic/asyncAwait2Replay_2.baseline

@@ -0,0 +1,3 @@
+4
+
+Reached end of Execution -- Exiting.

test/TTBasic/asyncAwait3.js

@@ -0,0 +1,25 @@
+//-------------------------------------------------------------------------------------------------------
+// Copyright (C) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE.txt file in the project root for full license information.
+//-------------------------------------------------------------------------------------------------------
+
+function resolveWait(x) {
+    return new Promise(resolve => {
+        WScript.SetTimeout(() => {
+            resolve(x);
+        }, 100);
+    });
+}
+
+async function awaitLater(x) {
+    const p_a = resolveWait(10);
+    const p_b = resolveWait(20);
+    return x + await p_a + await p_b;
+}
+
+WScript.SetTimeout(function () {
+    awaitLater(10).then(v => {
+        telemetryLog(v.toString(), true);
+        emitTTDLog(ttdLogURI);
+    });
+}, 0);

test/TTBasic/asyncAwait3Record.baseline

@@ -0,0 +1 @@
+40