[llvm] [AArch64][SME] Propagate desired ZA states in the MachineSMEABIPass (PR #149510)

[Benjamin Maxwell via llvm-commits]

================
@@ -918,6 +987,43 @@ bool MachineSMEABI::runOnMachineFunction(MachineFunction &MF) {
       getAnalysis<EdgeBundlesWrapperLegacy>().getEdgeBundles();
 
   FunctionInfo FnInfo = collectNeededZAStates(SMEFnAttrs);
+
+  if (OptLevel != CodeGenOptLevel::None) {
+    // Propagate desired states forwards then backwards. We propagate forwards
+    // first as this propagates desired states from inner to outer loops.
----------------
MacDue wrote:

I've updated this comment, let me know if it reads better now :+1: 

https://github.com/llvm/llvm-project/pull/149510