[llvm] [AArch64][SME2] Preserve ZT0 state around function calls (PR #78321)

[Sander de Smalen via llvm-commits]

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@@ -119,6 +119,12 @@ class SMEAttrs {
            State == StateValue::InOut || State == StateValue::Preserved;
   }
   bool hasZT0State() const { return isNewZT0() || sharesZT0(); }
+  bool requiresPreservingZT0(const SMEAttrs &Callee) const {
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sdesmalen-arm wrote:

Can we have unit tests for these in the file that tests this class?

https://github.com/llvm/llvm-project/pull/78321