[llvm] [AArch64][SME] Add remarks to flag lazy ZA saves, and SMSTART/SMSTOP transitions (PR #68255)

[Sander de Smalen via llvm-commits]

================
@@ -7388,13 +7401,32 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
         ISD::INTRINSIC_VOID, DL, MVT::Other, Chain,
         DAG.getConstant(Intrinsic::aarch64_sme_set_tpidr2, DL, MVT::i32),
         TPIDR2ObjAddr);
+    OptimizationRemarkEmitter ORE(&MF.getFunction());
+    ORE.emit([&]() {
+      auto R = CLI.CB ? OptimizationRemarkAnalysis(DEBUG_TYPE, "SMELazySaveZA",
+                                                   CLI.CB)
+                      : OptimizationRemarkAnalysis(DEBUG_TYPE, "SMELazySaveZA",
+                                                   &MF.getFunction());
+      DescribeCallsite(R) << " creates a lazy save ZA area";
----------------
sdesmalen-arm wrote:

nit:
```suggestion
      DescribeCallsite(R) << " sets up a lazy save for ZA";
```

https://github.com/llvm/llvm-project/pull/68255