From 955521eaf0809e379cdf43d21a16d89b016d1951 Mon Sep 17 00:00:00 2001
From: Alexander Shabalin <alexander.shabalin@jetbrains.com>
Date: Tue, 11 Aug 2020 21:01:45 +0300
Subject: [PATCH] Disable CycleDetector on WASM (#4325)

---
 backend.native/tests/build.gradle |  3 ++-
 runtime/src/main/cpp/Memory.cpp   | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/backend.native/tests/build.gradle b/backend.native/tests/build.gradle
index 3bd5610eb24..1bdaf4bcb81 100644
--- a/backend.native/tests/build.gradle
+++ b/backend.native/tests/build.gradle
@@ -2825,7 +2825,8 @@ task memory_stable_ref_cross_thread_check(type: KonanLocalTest) {
 }
 
 standaloneTest("cycle_detector") {
-    disabled = project.globalTestArgs.contains('-opt') || (project.testTarget == 'wasm32') // Needs debug build.
+    disabled = project.globalTestArgs.contains('-opt') || // Needs debug build.
+               (project.testTarget == 'wasm32') // CycleDetector is disabled on WASM.
     flags = ['-tr', '-g']
     source = "runtime/memory/cycle_detector.kt"
 }
diff --git a/runtime/src/main/cpp/Memory.cpp b/runtime/src/main/cpp/Memory.cpp
index 0e6e5207c5c..a830b922cc9 100644
--- a/runtime/src/main/cpp/Memory.cpp
+++ b/runtime/src/main/cpp/Memory.cpp
@@ -22,6 +22,14 @@
 // Allow concurrent global cycle collector.
 #define USE_CYCLIC_GC 0
 
+// CycleDetector internally uses static local with runtime initialization,
+// which requires atomics. Atomics are not available on WASM.
+#ifdef KONAN_WASM
+#define USE_CYCLE_DETECTOR 0
+#else
+#define USE_CYCLE_DETECTOR 1
+#endif
+
 #include "Alloc.h"
 #include "KAssert.h"
 #include "Atomic.h"
@@ -164,6 +172,8 @@ class ScopedRefHolder {
   KRef obj_ = nullptr;
 };
 
+#if USE_CYCLE_DETECTOR
+
 struct CycleDetectorRootset {
   // Orders roots.
   KStdVector<KRef> roots;
@@ -230,6 +240,8 @@ class CycleDetector {
   KStdUnorderedMap<KRef, CandidateList::iterator> candidateInList_;
 };
 
+#endif  // USE_CYCLE_DETECTOR
+
 // TODO: can we pass this variable as an explicit argument?
 THREAD_LOCAL_VARIABLE MemoryState* memoryState = nullptr;
 THREAD_LOCAL_VARIABLE FrameOverlay* currentFrame = nullptr;
@@ -1065,7 +1077,9 @@ ALWAYS_INLINE void runDeallocationHooks(ContainerHeader* container) {
       cyclicRemoveAtomicRoot(obj);
     }
 #endif  // USE_CYCLIC_GC
+#if USE_CYCLE_DETECTOR
     CycleDetector::removeCandidateIfNeeded(obj);
+#endif  // USE_CYCLE_DETECTOR
     if (obj->has_meta_object()) {
       ObjHeader::destroyMetaObject(&obj->typeInfoOrMeta_);
     }
@@ -2135,7 +2149,9 @@ OBJ_GETTER(allocInstance, const TypeInfo* type_info) {
     makeShareable(container.header());
   }
 #endif  // USE_GC
+#if USE_CYCLE_DETECTOR
   CycleDetector::insertCandidateIfNeeded(obj);
+#endif  // USE_CYCLE_DETECTOR
 #if USE_CYCLIC_GC
   if ((obj->type_info()->flags_ & TF_LEAK_DETECTOR_CANDIDATE) != 0) {
     // Note: this should be performed after [rememberNewContainer] (above).
@@ -2827,6 +2843,8 @@ ScopedRefHolder::~ScopedRefHolder() {
   }
 }
 
+#if USE_CYCLE_DETECTOR
+
 // static
 CycleDetectorRootset CycleDetector::collectRootset() {
   auto& detector = instance();
@@ -2934,6 +2952,8 @@ OBJ_GETTER(findCycle, KRef root) {
   RETURN_RESULT_OF(createAndFillArray, cycle);
 }
 
+#endif  // USE_CYCLE_DETECTOR
+
 }  // namespace
 
 MetaObjHeader* ObjHeader::createMetaObject(TypeInfo** location) {
@@ -3362,12 +3382,20 @@ KBoolean Kotlin_native_internal_GC_getTuneThreshold(KRef) {
 }
 
 OBJ_GETTER(Kotlin_native_internal_GC_detectCycles, KRef) {
+#if USE_CYCLE_DETECTOR
   if (!KonanNeedDebugInfo || !Kotlin_memoryLeakCheckerEnabled()) RETURN_OBJ(nullptr);
   RETURN_RESULT_OF0(detectCyclicReferences);
+#else
+  RETURN_OBJ(nullptr);
+#endif
 }
 
 OBJ_GETTER(Kotlin_native_internal_GC_findCycle, KRef, KRef root) {
+#if USE_CYCLE_DETECTOR
   RETURN_RESULT_OF(findCycle, root);
+#else
+  RETURN_OBJ(nullptr);
+#endif
 }
 
 KNativePtr CreateStablePointer(KRef any) {