Rollup merge of #93782 - adamgemmell:dev/adagem01/split-pauth, r=Amanieu

Split `pauth` target feature

Per discussion on https://github.com/rust-lang/rust/issues/86941 we'd like to split `pauth` into `paca` and `pacg` in order to better support possible future environments that only have the keys available for address or generic authentication. At the moment LLVM has the one `pauth` target_feature while Linux presents separate `paca` and `pacg` flags for feature detection.

Because the use of [target_feature](https://rust-lang.github.io/rfcs/2045-target-feature.html) will "allow the compiler to generate code under the assumption that this code will only be reached in hosts that support the feature", it does not make sense to simply translate `paca` into the LLVM feature `pauth`, as it will generate code as if `pacg` is available.

To accommodate this we error if only one of the two features is present. If LLVM splits them in the future we can remove this restriction without making a breaking change.

r? ```@Amanieu```

1 files changed, 13 insertions, 2 deletions

diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index 63cc6faf9ec..f31b0ee592e 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -74,8 +74,10 @@ const AARCH64_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     ("ssbs", Some(sym::aarch64_target_feature)),
     // FEAT_SB
     ("sb", Some(sym::aarch64_target_feature)),
-    // FEAT_PAUTH
-    ("pauth", Some(sym::aarch64_target_feature)),
+    // FEAT_PAUTH (address authentication)
+    ("paca", Some(sym::aarch64_target_feature)),
+    // FEAT_PAUTH (generic authentication)
+    ("pacg", Some(sym::aarch64_target_feature)),
     // FEAT_DPB
     ("dpb", Some(sym::aarch64_target_feature)),
     // FEAT_DPB2
@@ -137,6 +139,8 @@ const AARCH64_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     ("v8.7a", Some(sym::aarch64_target_feature)),
 ];
 
+const AARCH64_TIED_FEATURES: &[&[&str]] = &[&["paca", "pacg"]];
+
 const X86_ALLOWED_FEATURES: &[(&str, Option<Symbol>)] = &[
     ("adx", Some(sym::adx_target_feature)),
     ("aes", None),
@@ -256,6 +260,13 @@ pub fn supported_target_features(sess: &Session) -> &'static [(&'static str, Opt
     }
 }
 
+pub fn tied_target_features(sess: &Session) -> &'static [&'static [&'static str]] {
+    match &*sess.target.arch {
+        "aarch64" => AARCH64_TIED_FEATURES,
+        _ => &[],
+    }
+}
+
 pub(crate) fn provide(providers: &mut Providers) {
     providers.supported_target_features = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);