[llvm] Reland "[AArch64][SME] Split SMECallAttrs out of SMEAttrs" (PR #138671)

[Sander de Smalen via llvm-commits]

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@@ -99,17 +77,48 @@ SMEAttrs::SMEAttrs(const AttributeList &Attrs) {
     Bitmask |= encodeZT0State(StateValue::New);
 }
 
-bool SMEAttrs::requiresSMChange(const SMEAttrs &Callee) const {
-  if (Callee.hasStreamingCompatibleInterface())
+void SMEAttrs::addKnownFunctionAttrs(StringRef FuncName) {
+  unsigned KnownAttrs = SMEAttrs::Normal;
+  if (FuncName == "__arm_tpidr2_save" || FuncName == "__arm_sme_state")
+    KnownAttrs |= (SMEAttrs::SM_Compatible | SMEAttrs::SME_ABI_Routine);
+  if (FuncName == "__arm_tpidr2_restore")
+    KnownAttrs |= SMEAttrs::SM_Compatible | encodeZAState(StateValue::In) |
+                  SMEAttrs::SME_ABI_Routine;
+  if (FuncName == "__arm_sc_memcpy" || FuncName == "__arm_sc_memset" ||
+      FuncName == "__arm_sc_memmove" || FuncName == "__arm_sc_memchr")
+    KnownAttrs |= SMEAttrs::SM_Compatible;
+  if (FuncName == "__arm_sme_save" || FuncName == "__arm_sme_restore" ||
+      FuncName == "__arm_sme_state_size")
+    KnownAttrs |= SMEAttrs::SM_Compatible | SMEAttrs::SME_ABI_Routine;
+  set(KnownAttrs, /*Enable=*/true);
----------------
sdesmalen-arm wrote:

nit:
```suggestion
  set(KnownAttrs);
```

https://github.com/llvm/llvm-project/pull/138671