tor-browser

commit 2cf89694835ff74c2efacb1950b271d31d27f297
parent bacf29978d812f7178c3dfa9e5021d1c95c7c5eb
Author: Ryan Hunt <rhunt@eqrion.net>
Date:   Thu, 18 Dec 2025 16:45:25 +0000

Bug 2002625 - wasm: Remove onSuspendableStack flag. r=yury

We can just use `activeSuspender` for this and reduce the
amount of state we need to update.

Differential Revision: https://phabricator.services.mozilla.com/D274185

Diffstat:
M
js/src/wasm/WasmContext.cpp
 | 
9
+--------
M
js/src/wasm/WasmContext.h
 | 
17
++++++++---------
M
js/src/wasm/WasmFrameIter.cpp
 | 
9
++++-----
M
js/src/wasm/WasmPI.cpp
 | 
2
+-

4 files changed, 14 insertions(+), 23 deletions(-)
diff --git a/js/src/wasm/WasmContext.cpp b/js/src/wasm/WasmContext.cpp
@@ -33,7 +33,6 @@ Context::Context()
 #ifdef ENABLE_WASM_JSPI
       ,
       activeSuspender_(nullptr),
-      onSuspendableStack(0),
       suspendableStacksCount(0),
       suspendedStacks_()
 #endif
@@ -54,8 +53,6 @@ void Context::initStackLimit(JSContext* cx) {
 }
 
 #ifdef ENABLE_WASM_JSPI
-SuspenderObject* Context::activeSuspender() { return activeSuspender_; }
-
 void Context::trace(JSTracer* trc) {
   if (activeSuspender_) {
     TraceEdge(trc, &activeSuspender_, "suspender");
@@ -78,23 +75,19 @@ void Context::traceRoots(JSTracer* trc) {
 
 void Context::enterSuspendableStack(SuspenderObject* suspender,
                                     JS::NativeStackLimit newStackLimit) {
-  MOZ_ASSERT(onSuspendableStack == 0);
   MOZ_ASSERT(!activeSuspender_);
   activeSuspender_ = suspender;
-  onSuspendableStack = 1;
   stackLimit = newStackLimit;
 }
 
 void Context::leaveSuspendableStack(JSContext* cx) {
-  MOZ_ASSERT(onSuspendableStack != 0);
   MOZ_ASSERT(activeSuspender_);
   activeSuspender_ = nullptr;
-  onSuspendableStack = 0;
   initStackLimit(cx);
 }
 
 bool js::IsSuspendableStackActive(JSContext* cx) {
-  return cx->wasm().onSuspendableStack != 0;
+  return cx->wasm().onSuspendableStack();
 }
 
 JS::NativeStackLimit js::GetSuspendableStackLimit(JSContext* cx) {
diff --git a/js/src/wasm/WasmContext.h b/js/src/wasm/WasmContext.h
@@ -45,16 +45,16 @@ class Context {
   static constexpr size_t offsetOfStackLimit() {
     return offsetof(Context, stackLimit);
   }
-#ifdef ENABLE_WASM_JSPI
-  static constexpr size_t offsetOfOnSuspendableStack() {
-    return offsetof(Context, onSuspendableStack);
-  }
-#endif
 
   void initStackLimit(JSContext* cx);
 
 #ifdef ENABLE_WASM_JSPI
-  SuspenderObject* activeSuspender();
+  static constexpr size_t offsetOfActiveSuspender() {
+    return offsetof(Context, activeSuspender_);
+  }
+
+  SuspenderObject* activeSuspender() { return activeSuspender_; }
+  bool onSuspendableStack() const { return activeSuspender_ != nullptr; }
 
   void enterSuspendableStack(SuspenderObject* suspender,
                              JS::NativeStackLimit newStackLimit);
@@ -75,10 +75,9 @@ class Context {
   JS::NativeStackLimit stackLimit;
 
 #ifdef ENABLE_WASM_JSPI
+  // The currently active suspender object. Null if we're executing on the
+  // system stack, otherwise we're on a wasm suspendable stack.
   HeapPtr<SuspenderObject*> activeSuspender_;
-  // Boolean value set to true when the top wasm frame is currently executed on
-  // a suspendable stack. Aligned to int32_t to be used on JIT code.
-  int32_t onSuspendableStack;
   mozilla::Atomic<uint32_t> suspendableStacksCount;
   // Using double-linked list to avoid allocation in the JIT code.
   mozilla::DoublyLinkedList<SuspenderObjectData> suspendedStacks_;
diff --git a/js/src/wasm/WasmFrameIter.cpp b/js/src/wasm/WasmFrameIter.cpp
@@ -1008,11 +1008,10 @@ void wasm::GenerateJitExitPrologue(MacroAssembler& masm,
 
     const Register scratch = ABINonArgReg0;
     masm.loadPtr(Address(InstanceReg, Instance::offsetOfCx()), scratch);
-    masm.load32(
-        Address(scratch, JSContext::offsetOfWasm() +
-                             wasm::Context::offsetOfOnSuspendableStack()),
-        scratch);
-    masm.branchTest32(Assembler::NonZero, scratch, scratch, &fallback);
+    masm.loadPtr(Address(scratch, JSContext::offsetOfWasm() +
+                                      wasm::Context::offsetOfActiveSuspender()),
+                 scratch);
+    masm.branchTestPtr(Assembler::NonZero, scratch, scratch, &fallback);
   }
 
   uint32_t entryOffset;
diff --git a/js/src/wasm/WasmPI.cpp b/js/src/wasm/WasmPI.cpp
@@ -443,7 +443,7 @@ void SuspenderObject::leave(JSContext* cx) {
       break;
     }
     case SuspenderState::Suspended: {
-      MOZ_ASSERT(cx->wasm().onSuspendableStack == 0);
+      MOZ_ASSERT(!cx->wasm().onSuspendableStack());
       break;
     }
     case SuspenderState::Initial: