[clang] [AArch64][Clang] Add support for __arm_agnostic("sme_za_state") (PR #121788)

[Benjamin Maxwell via cfe-commits]

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@@ -4593,9 +4593,14 @@ class FunctionType : public Type {
     SME_ZT0Shift = 5,
     SME_ZT0Mask = 0b111 << SME_ZT0Shift,
 
+    // A bit to tell whether a function is agnostic about sme ZA state.
+    SME_AgnosticZAStateShift = 8,
+    SME_AgnosticZAStateMask = 1 << SME_AgnosticZAStateShift,
+
     SME_AttributeMask =
-        0b111'111'11 // We can't support more than 8 bits because of
-                     // the bitmask in FunctionTypeExtraBitfields.
+        0b1'111'111'11 // We can't support more than 16 bits because of
+                       // the bitmask in FunctionTypeArmAttributes
+                       // and ExtProtoInfo.
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MacDue wrote:

Looks like it's 9 bits (in FunctionTypeArmAttributes and ExtProtoInfo), not 16 bits? 

https://github.com/llvm/llvm-project/pull/121788