[llvm] [AArch64][SME] Implement the SME ABI (ZA state management) in Machine IR (PR #149062)

[via llvm-commits]

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@@ -9209,10 +9234,20 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
         AArch64ISD::SMSTOP, DL, DAG.getVTList(MVT::Other, MVT::Glue), Chain,
         DAG.getTargetConstant((int32_t)(AArch64SVCR::SVCRZA), DL, MVT::i32));
 
-  // Adjust the stack pointer for the new arguments...
+  // Adjust the stack pointer for the new arguments... and mark ZA uses.
   // These operations are automatically eliminated by the prolog/epilog pass
-  if (!IsSibCall)
+  assert((!IsSibCall || !ZAMarkerNode) && "ZA markers require CALLSEQ_START");
+  if (!IsSibCall) {
     Chain = DAG.getCALLSEQ_START(Chain, IsTailCall ? 0 : NumBytes, 0, DL);
+    if (ZAMarkerNode) {
+      // Note: We need the CALLSEQ_START to glue the ZAMarkerNode to, simply
+      // using a chain can result in incorrect scheduling. The markers refer to
+      // the position just before the CALLSEQ_START (though occur after as
+      // CALLSEQ_START lacks in-glue).
+      Chain = DAG.getNode(*ZAMarkerNode, DL, DAG.getVTList(MVT::Other),
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kanompiebear-arch wrote:

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https://github.com/llvm/llvm-project/pull/149062