[llvm] [NVPTX] Add syncscope support for cmpxchg (PR #140812)

[via llvm-commits]

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@@ -303,6 +304,7 @@ bool AtomicExpandImpl::processAtomicInstr(Instruction *I) {
 
   if (TLI->shouldInsertFencesForAtomic(I)) {
     auto FenceOrdering = AtomicOrdering::Monotonic;
+    SyncScope::ID SSID = SyncScope::System;
     if (LI && isAcquireOrStronger(LI->getOrdering())) {
       FenceOrdering = LI->getOrdering();
       LI->setOrdering(AtomicOrdering::Monotonic);
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gonzalobg wrote:

I was expecting load, store, and rmw to require changes here as well.
If the intent is to incrementally improve it for CAS only, it may make sense to leave a TODO comment on these to call that out.

https://github.com/llvm/llvm-project/pull/140812