[Clang][AArch64] Change SME attributes for shared/new/preserved state. (#76971)

This patch replaces the `__arm_new_za`, `__arm_shared_za` and
`__arm_preserves_za` attributes in favour of:
* `__arm_new("za")`
* `__arm_in("za")`
* `__arm_out("za")`
* `__arm_inout("za")`
* `__arm_preserves("za")`

As described in https://github.com/ARM-software/acle/pull/276.

One change is that `__arm_in/out/inout/preserves(S)` are all mutually
exclusive, whereas previously it was fine to write `__arm_shared_za
__arm_preserves_za`. This case is now represented with `__arm_in("za")`.

The current implementation uses the same LLVM attributes under the hood,
since `__arm_in/out/inout` are all variations of "shared ZA", so can use
the existing `aarch64_pstate_za_shared` attribute in LLVM.

#77941 will add support for the new "zt0" state as introduced
with SME2.

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index ed684c5d..8d856cc2 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -6791,7 +6791,13 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
     } else if (Tok.isRegularKeywordAttribute()) {
       // For consistency with attribute parsing.
       Diag(Tok, diag::err_keyword_not_allowed) << Tok.getIdentifierInfo();
+      bool TakesArgs = doesKeywordAttributeTakeArgs(Tok.getKind());
       ConsumeToken();
+      if (TakesArgs) {
+        BalancedDelimiterTracker T(*this, tok::l_paren);
+        if (!T.consumeOpen())
+          T.skipToEnd();
+      }
     } else if (Tok.is(tok::kw_requires) && D.hasGroupingParens()) {
       // This declarator is declaring a function, but the requires clause is
       // in the wrong place: