[llvm] [AArch64][SME] Allow memory operations lowering to custom SME functions. (PR #79263)

[Sander de Smalen via llvm-commits]

================
@@ -76,15 +82,85 @@ SDValue AArch64SelectionDAGInfo::EmitMOPS(AArch64ISD::NodeType SDOpcode,
   }
 }
 
+SDValue AArch64SelectionDAGInfo::EmitSpecializedLibcall(
+    SelectionDAG &DAG, const SDLoc &DL, SDValue Chain, SDValue Dst, SDValue Src,
+    SDValue Size, RTLIB::Libcall LC) const {
+  const AArch64Subtarget &STI =
+      DAG.getMachineFunction().getSubtarget<AArch64Subtarget>();
+  const AArch64TargetLowering *TLI = STI.getTargetLowering();
+  TargetLowering::ArgListTy Args;
+  TargetLowering::ArgListEntry DstEntry;
+  SDValue Symbol;
+  DstEntry.Ty = PointerType::getUnqual(*DAG.getContext());
+  DstEntry.Node = Dst;
+  Args.push_back(DstEntry);
+  EVT Ty = TLI->getPointerTy(DAG.getDataLayout());
+  PointerType *RetTy;
+
+  if (!LowerToSMERoutines)
+    return SDValue();
+
+  switch (LC) {
+  case RTLIB::MEMCPY: {
+    TargetLowering::ArgListEntry Entry;
+    Entry.Ty = PointerType::getUnqual(*DAG.getContext());
+    Symbol = DAG.getExternalSymbol("__arm_sc_memcpy", Ty);
+    Entry.Node = Src;
+    Args.push_back(Entry);
+    RetTy = PointerType::getUnqual(*DAG.getContext());
+    break;
+  }
+  case RTLIB::MEMMOVE: {
+    TargetLowering::ArgListEntry Entry;
+    Entry.Ty = PointerType::getUnqual(*DAG.getContext());
+    Symbol = DAG.getExternalSymbol("__arm_sc_memmove", Ty);
+    Entry.Node = Src;
+    Args.push_back(Entry);
+    RetTy = PointerType::getUnqual(*DAG.getContext());
+    break;
+  }
+  case RTLIB::MEMSET: {
+    TargetLowering::ArgListEntry Entry;
+    Entry.Ty = Type::getInt32Ty(*DAG.getContext());
+    Symbol = DAG.getExternalSymbol("__arm_sc_memset", Ty);
+    Src = DAG.getZExtOrTrunc(Src, DL, MVT::i32);
+    Entry.Node = Src;
+    Args.push_back(Entry);
+    RetTy = PointerType::getUnqual(*DAG.getContext());
+    break;
+  }
+  default:
+    return SDValue();
+  }
+  TargetLowering::ArgListEntry SizeEntry;
+  SizeEntry.Node = Size;
+  SizeEntry.Ty = PointerType::getUnqual(*DAG.getContext());
+  Args.push_back(SizeEntry);
+  assert(Symbol->getOpcode() == ISD::ExternalSymbol &&
+         "Function name is not set");
+
+  TargetLowering::CallLoweringInfo CLI(DAG);
+  CLI.setDebugLoc(DL).setChain(Chain).setLibCallee(
+      TLI->getLibcallCallingConv(LC), RetTy, Symbol, std::move(Args));
+  std::pair<SDValue, SDValue> CallResult = TLI->LowerCallTo(CLI);
+  return (isa<PointerType>(RetTy) ? CallResult.second : CallResult.first);
----------------
sdesmalen-arm wrote:

If you name this function appropriately (see my suggestion above), this can be reverted back to be:
```suggestion
  return TLI->LowerCallTo(CLI).second;
```

https://github.com/llvm/llvm-project/pull/79263