rustc_target: Add more RISC-V atomic-related features

Author: taiki-e

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -281,6 +281,8 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
         ("riscv32" | "riscv64", "zaamo") if get_version().0 < 19 => None,
         ("riscv32" | "riscv64", "zabha") if get_version().0 < 19 => None,
         ("riscv32" | "riscv64", "zalrsc") if get_version().0 < 19 => None,
+        ("riscv32" | "riscv64", "zama16b") if get_version().0 < 19 => None,
+        ("riscv32" | "riscv64", "zacas") if get_version().0 < 20 => None,
         // Enable the evex512 target feature if an avx512 target feature is enabled.
         ("x86", s) if s.starts_with("avx512") => {
             Some(LLVMFeature::with_dependency(s, TargetFeatureFoldStrength::EnableOnly("evex512")))

compiler/rustc_target/src/target_features.rs

@@ -497,9 +497,14 @@ static RISCV_FEATURES: &[(&str, Stability, ImpliedFeatures)] = &[
     ("relax", Unstable(sym::riscv_target_feature), &[]),
     ("unaligned-scalar-mem", Unstable(sym::riscv_target_feature), &[]),
     ("v", Unstable(sym::riscv_target_feature), &[]),
+    ("za128rs", Unstable(sym::riscv_target_feature), &[]),
+    ("za64rs", Unstable(sym::riscv_target_feature), &[]),
     ("zaamo", Unstable(sym::riscv_target_feature), &[]),
     ("zabha", Unstable(sym::riscv_target_feature), &["zaamo"]),
+    ("zacas", Unstable(sym::riscv_target_feature), &["zaamo"]),
     ("zalrsc", Unstable(sym::riscv_target_feature), &[]),
+    ("zama16b", Unstable(sym::riscv_target_feature), &[]),
+    ("zawrs", Unstable(sym::riscv_target_feature), &[]),
     ("zba", Stable, &[]),
     ("zbb", Stable, &[]),
     ("zbc", Stable, &[]),

tests/ui/check-cfg/target_feature.stderr

@@ -279,9 +279,14 @@ LL |     cfg!(target_feature = "_UNEXPECTED_VALUE");
 `xsavec`
 `xsaveopt`
 `xsaves`
+`za128rs`
+`za64rs`
 `zaamo`
 `zabha`
+`zacas`
 `zalrsc`
+`zama16b`
+`zawrs`
 `zba`
 `zbb`
 `zbc`