[llvm] [NVPTX] Load/Store/Fence syncscope support (PR #106101)

[Artem Belevich via llvm-commits]

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@@ -4064,3 +4158,43 @@ unsigned NVPTXDAGToDAGISel::GetConvertOpcode(MVT DestTy, MVT SrcTy,
     }
   }
 }
+
+bool NVPTXDAGToDAGISel::tryFence(SDNode *N) {
+  SDLoc DL(N);
+  assert(N->getOpcode() == ISD::ATOMIC_FENCE);
+  unsigned int FenceOp =
+      getFenceOp(NVPTX::Ordering(N->getConstantOperandVal(1)),
+                 Scopes[N->getConstantOperandVal(2)], Subtarget);
+  SDValue Chain = N->getOperand(0);
+  SDNode *FenceNode = CurDAG->getMachineNode(FenceOp, DL, MVT::Other, Chain);
+  ReplaceNode(N, FenceNode);
+  return true;
+}
+
+NVPTXScopes::NVPTXScopes(LLVMContext &C) : CTX(&C) {
+  Scopes[C.getOrInsertSyncScopeID("singlethread")] = NVPTX::Scope::Thread;
+  Scopes[C.getOrInsertSyncScopeID("")] = NVPTX::Scope::System;
+  Scopes[C.getOrInsertSyncScopeID("block")] = NVPTX::Scope::Block;
+  Scopes[C.getOrInsertSyncScopeID("cluster")] = NVPTX::Scope::Cluster;
+  Scopes[C.getOrInsertSyncScopeID("device")] = NVPTX::Scope::Device;
+}
+
+NVPTX::Scope NVPTXScopes::operator[](SyncScope::ID ID) const {
+  if (Scopes.empty())
+    report_fatal_error("NVPTX Scopes must be initialized before calling "
+                       "NVPTXScopes::operator[]");
+
+  auto S = Scopes.find(ID);
+  if (S == Scopes.end()) {
+    SmallVector<StringRef, 8> ScopeNames;
+    assert(CTX != nullptr && "CTX is nullptr");
+    CTX->getSyncScopeNames(ScopeNames);
+    StringRef Unknown{"unknown"};
+    auto Name = ID < ScopeNames.size() ? ScopeNames[ID] : Unknown;
+    report_fatal_error(
+        formatv("Could not find scope ID={} with name \"{}\".", int(ID), Name));
----------------
Artem-B wrote:

> The scope discovery and map creation is done elsewhere once.

That's exactly the point.

Right now context only provides you with **all** the known scope names via `getSyncScopeNames()`. So you end up first copying all the names, and then index into that array, which, AFAICT, depends on the implementation detail which assumes that returned names are in the ID order, with no gaps, etc.

You only need the name of the specific ID.
I propose to extend context API and add `getScopeName(ID)` which will return the name that ID was registered with.


https://github.com/llvm/llvm-project/pull/106101