[llvm] [SPIR-V] Align memory scopes with SPIR-V specification and LLVM expectations and change default mem scope value (PR #108528)

[Matt Arsenault via llvm-commits]

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@@ -36,19 +36,22 @@
 namespace {
 
 struct SyncScopeIDs {
-  llvm::SyncScope::ID Work_ItemSSID;
+  // Init SubGroupSSID with the reserved (invalid for SubGroupSSID) value to be
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arsenm wrote:

I would assume Work_ItemSSID = SingleThread, not subgroup 

https://github.com/llvm/llvm-project/pull/108528