[clang] [llvm] [BPF] Add load-acquire and store-release instructions under -mcpu=v4 (PR #108636)

[Peilin Ye via llvm-commits]

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@@ -703,6 +715,39 @@ SDValue BPFTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
   return DAG.getNode(BPFISD::SELECT_CC, DL, VTs, Ops);
 }
 
+SDValue BPFTargetLowering::LowerATOMIC_LOAD(SDValue Op,
+                                            SelectionDAG &DAG) const {
+  const char *Msg =
+      "sequentially consistent (seq_cst) atomic load is not supported";
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peilin-ye wrote:

OK, let me change it in the next push.

> Plus I think such an error should be relegated to an unsupported legalize action.

Sorry, could you explain your suggestion a bit more?  Are you suggesting that we add an `Unsupported` enum value to `LegalizeAction`?

https://github.com/llvm/llvm-project/pull/108636