[llvm] [AArch64][SME] Split SMECallAttrs out of SMEAttrs (PR #137239)

[Sander de Smalen via llvm-commits]

================
@@ -126,27 +122,87 @@ class SMEAttrs {
   bool isPreservesZT0() const {
     return decodeZT0State(Bitmask) == StateValue::Preserved;
   }
-  bool isUndefZT0() const { return Bitmask & ZT0_Undef; }
+  bool hasUndefZT0() const { return Bitmask & ZT0_Undef; }
   bool sharesZT0() const {
     StateValue State = decodeZT0State(Bitmask);
     return State == StateValue::In || State == StateValue::Out ||
            State == StateValue::InOut || State == StateValue::Preserved;
   }
   bool hasZT0State() const { return isNewZT0() || sharesZT0(); }
-  bool requiresPreservingZT0(const SMEAttrs &Callee) const {
-    return hasZT0State() && !Callee.isUndefZT0() && !Callee.sharesZT0() &&
-           !Callee.hasAgnosticZAInterface();
+
+  SMEAttrs operator|(SMEAttrs Other) const {
+    SMEAttrs Merged(*this);
+    Merged.set(Other.Bitmask, /*Enable=*/true);
+    return Merged;
   }
-  bool requiresDisablingZABeforeCall(const SMEAttrs &Callee) const {
-    return hasZT0State() && !hasZAState() && Callee.hasPrivateZAInterface() &&
-           !(Callee.Bitmask & SME_ABI_Routine);
+
+  SMEAttrs withoutPerCallsiteFlags() const {
+    return (Bitmask & ~Callsite_Flags);
   }
-  bool requiresEnablingZAAfterCall(const SMEAttrs &Callee) const {
-    return requiresLazySave(Callee) || requiresDisablingZABeforeCall(Callee);
+
+  bool operator==(SMEAttrs const &Other) const {
+    return Bitmask == Other.Bitmask;
   }
-  bool requiresPreservingAllZAState(const SMEAttrs &Callee) const {
-    return hasAgnosticZAInterface() && !Callee.hasAgnosticZAInterface() &&
-           !(Callee.Bitmask & SME_ABI_Routine);
+
+private:
+  void addKnownFunctionAttrs(StringRef FuncName);
+};
+
+/// SMECallAttrs is a utility class to hold the SMEAttrs for a callsite. It has
+/// interfaces to query whether a streaming mode change or lazy-save mechanism
+/// is required when going from one function to another (e.g. through a call).
+class SMECallAttrs {
+  SMEAttrs CallerFn;
+  SMEAttrs CalledFn;
+  SMEAttrs Callsite;
+  bool IsIndirect = false;
+
+public:
+  SMECallAttrs(SMEAttrs Caller, SMEAttrs Callee,
+               SMEAttrs Callsite = SMEAttrs::Normal)
+      : CallerFn(Caller), CalledFn(Callee), Callsite(Callsite) {}
+
+  SMECallAttrs(const CallBase &CB);
+
+  SMEAttrs &caller() { return CallerFn; }
+  SMEAttrs &callee() {
+    if (IsIndirect)
+      return Callsite;
+    return CalledFn;
+  }
----------------
sdesmalen-arm wrote:

nit:
```suggestion
  SMEAttrs &callee() { return IsIndirect ? Callsite : CalledFn; }
```

https://github.com/llvm/llvm-project/pull/137239