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

[Paul Walker via llvm-commits]

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@@ -9171,10 +9191,21 @@ 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.has_value()) &&
+         "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 referer
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paulwalker-arm wrote:

s/referer/refer/ ?

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