std_detect: loongarch: Add runtime detectable features from LLVM

* f
* d
* frecipe
* lbt

Author: heiher

crates/std_detect/src/detect/arch/loongarch.rs

@@ -8,17 +8,29 @@ features! {
     /// Checks if `loongarch` feature is enabled.
     /// Supported arguments are:
     ///
-    /// * `"ual"`
+    /// * `"f"`
+    /// * `"d"`
+    /// * `"frecipe"`
     /// * `"lsx"`
     /// * `"lasx"`
+    /// * `"lbt"`
     /// * `"lvz"`
+    /// * `"ual"`
     #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")]
-    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] ual: "ual";
-    /// UAL
+    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] f: "f";
+    /// F
+    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] d: "d";
+    /// D
+    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] frecipe: "frecipe";
+    /// Frecipe
     @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] lsx: "lsx";
     /// LSX
     @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] lasx: "lasx";
     /// LASX
+    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] lbt: "lbt";
+    /// LBT
     @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] lvz: "lvz";
     /// LVZ
+    @FEATURE: #[unstable(feature = "stdarch_loongarch_feature_detection", issue = "117425")] ual: "ual";
+    /// UAL
 }

crates/std_detect/src/detect/os/linux/loongarch.rs

@@ -2,6 +2,7 @@
 
 use super::auxvec;
 use crate::detect::{bit, cache, Feature};
+use core::arch::asm;
 
 /// Try to read the features from the auxiliary vector.
 pub(crate) fn detect_features() -> cache::Initializer {
@@ -12,14 +13,42 @@ pub(crate) fn detect_features() -> cache::Initializer {
         }
     };
 
+    // The values are part of the platform-specific [cpucfg]
+    //
+    // [cpucfg]: LoongArch Reference Manual Volume 1: Basic Architecture v1.1
+    let cpucfg2: usize;
+    unsafe {
+        asm!(
+            "cpucfg {}, {}",
+            out(reg) cpucfg2, in(reg) 2,
+            options(pure, nomem, preserves_flags, nostack)
+        );
+    }
+    enable_feature(&mut value, Feature::frecipe, bit::test(cpucfg2, 25));
+
     // The values are part of the platform-specific [asm/hwcap.h][hwcap]
     //
     // [hwcap]: https://github.com/torvalds/linux/blob/master/arch/loongarch/include/uapi/asm/hwcap.h
     if let Ok(auxv) = auxvec::auxv() {
-        enable_feature(&mut value, Feature::ual, bit::test(auxv.hwcap, 2));
+        enable_feature(
+            &mut value,
+            Feature::f,
+            bit::test(cpucfg2, 1) && bit::test(auxv.hwcap, 3),
+        );
+        enable_feature(
+            &mut value,
+            Feature::d,
+            bit::test(cpucfg2, 2) && bit::test(auxv.hwcap, 3),
+        );
         enable_feature(&mut value, Feature::lsx, bit::test(auxv.hwcap, 4));
         enable_feature(&mut value, Feature::lasx, bit::test(auxv.hwcap, 5));
+        enable_feature(
+            &mut value,
+            Feature::lbt,
+            bit::test(auxv.hwcap, 10) && bit::test(auxv.hwcap, 11) && bit::test(auxv.hwcap, 12),
+        );
         enable_feature(&mut value, Feature::lvz, bit::test(auxv.hwcap, 9));
+        enable_feature(&mut value, Feature::ual, bit::test(auxv.hwcap, 2));
         return value;
     }
     value