aarch64: Support FEAT_LRCPC3/FEAT_LSE128 with pre-16 LLVM

LLVM supports FEAT_LRCPC3/FEAT_LSE128 instructions on LLVM 16+, so use .inst directive on old LLVM.
llvm/llvm-project@a6aaa96
llvm/llvm-project@7fea6f2

AAarch64 .inst directive is portable since LLVM 7:
llvm/llvm-project@3e3d39d

.github/.cspell/project-dictionary.txt

@@ -64,8 +64,14 @@ kuser
 ldar
 ldaxp
 ldclrp
+ldclrpa
+ldclrpal
+ldclrpl
 ldiapp
 ldsetp
+ldsetpa
+ldsetpal
+ldsetpl
 ldxp
 lghi
 libatomic
@@ -149,6 +155,9 @@ subfe
 subfic
 subfze
 swpp
+swppa
+swppal
+swppl
 syscall
 sysctlbyname
 sysctlnode

.github/workflows/ci.yml

@@ -134,8 +134,8 @@ jobs:
             target: aarch64-unknown-linux-gnu
           # - rust: '1.64' # LLVM 14
           #   target: aarch64-unknown-linux-gnu
-          # - rust: '1.69' # LLVM 15
-          #   target: aarch64-unknown-linux-gnu
+          - rust: '1.69' # LLVM 15
+            target: aarch64-unknown-linux-gnu
           # - rust: '1.72' # LLVM 16
           #   target: aarch64-unknown-linux-gnu
           - rust: stable

build.rs

@@ -235,13 +235,8 @@ fn main() {
                 let is_macos = target_os == "macos";
                 let mut has_lse = is_macos;
                 target_feature_fallback("lse2", is_macos);
-                // LLVM supports FEAT_LRCPC3 and FEAT_LSE128 on LLVM 16+:
-                // https://github.com/llvm/llvm-project/commit/a6aaa969f7caec58a994142f8d855861cf3a1463
-                // https://github.com/llvm/llvm-project/commit/7fea6f2e0e606e5339c3359568f680eaf64aa306
-                if version.llvm >= 16 {
-                    has_lse |= target_feature_fallback("lse128", false);
-                    target_feature_fallback("rcpc3", false);
-                }
+                has_lse |= target_feature_fallback("lse128", false);
+                target_feature_fallback("rcpc3", false);
                 // aarch64_target_feature stabilized in Rust 1.61.
                 if needs_target_feature_fallback(&version, Some(61)) {
                     target_feature_fallback("lse", has_lse);