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

[Sander de Smalen via llvm-commits]

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@@ -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",
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sdesmalen-arm wrote:

nit: Rather than using `DEBUG_TYPE/aarch64-lower`, can we use `sme` instead? I'm not sure if there will be other places where we want to emit any SME-specific remarks, at which point the end-user can simply do `-Rpass-analysis=sme`.

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