[llvm] [AArch64][SME2] Extend SMEABIPass to handle functions with new ZT0 state (PR #78848)

[Kerry McLaughlin via llvm-commits]

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@@ -49,11 +49,13 @@ SMEAttrs::SMEAttrs(const CallBase &CB) {
 
 SMEAttrs::SMEAttrs(StringRef FuncName) : Bitmask(0) {
   if (FuncName == "__arm_tpidr2_save" || FuncName == "__arm_sme_state")
-    Bitmask |= (SMEAttrs::SM_Compatible | SMEAttrs::ZA_Preserved |
-                SMEAttrs::ZA_NoLazySave);
+    Bitmask |=
+        (SMEAttrs::SM_Compatible | SMEAttrs::ZA_Preserved |
+         SMEAttrs::ZA_NoLazySave | encodeZT0State(StateValue::Preserved));
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kmclaughlin-arm wrote:

I've removed the Preserved attribute from these functions for now, which means we generate a spill/fill of ZT0 around these calls from a `aarch64_new_zt0` function and also call `smstop za`/`smstart za` when the caller does not also have ZA state.

https://github.com/llvm/llvm-project/pull/78848