[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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@@ -7362,6 +7363,18 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
   else if (auto *ES = dyn_cast<ExternalSymbolSDNode>(CLI.Callee))
     CalleeAttrs = SMEAttrs(ES->getSymbol());
 
+  auto DescribeCallsite =
+      [&](OptimizationRemarkAnalysis &R) -> OptimizationRemarkAnalysis & {
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sdesmalen-arm wrote:

I'm a bit weary of writing code in anticipation of future changes which may never happen. We can always rewrite the code in this form later if that makes more sense. That said, I don't feel too strongly about it since the current code isn't bad either.

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