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

[Sander de Smalen via llvm-commits]

================
@@ -43,18 +40,25 @@ class SMEAttrs {
     SM_Body = 1 << 2,         // aarch64_pstate_sm_body
     SME_ABI_Routine = 1 << 3, // Used for SME ABI routines to avoid lazy saves
     ZA_State_Agnostic = 1 << 4,
-    ZT0_Undef = 1 << 5,       // Use to mark ZT0 as undef to avoid spills
+    ZT0_Undef = 1 << 5, // Use to mark ZT0 as undef to avoid spills
     ZA_Shift = 6,
     ZA_Mask = 0b111 << ZA_Shift,
     ZT0_Shift = 9,
-    ZT0_Mask = 0b111 << ZT0_Shift
+    ZT0_Mask = 0b111 << ZT0_Shift,
+    Callsite_Flags = ZT0_Undef
----------------
sdesmalen-arm wrote:

nit: `CallSiteFlags_Mask` ?

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