LoongArch: Add glibc.cpu.hwcap support.

Key Points:
1. On lasx & lsx platforms, We must use _dl_runtime_{profile, resolve}_{lsx, lasx}
   to save vector registers.
2. Via "tunables", users can choose str/mem_{lasx,lsx,unaligned} functions with
   `export GLIBC_TUNABLES=glibc.cpu.hwcaps=LASX,...`.
   Note: glibc.cpu.hwcaps doesn't affect _dl_runtime_{profile, resolve}_{lsx, lasx}
   selection.

Usage Notes:
1. Only valid inputs: LASX, LSX, UAL. Case-sensitive, comma-separated, no spaces.
2. Example: `export GLIBC_TUNABLES=glibc.cpu.hwcaps=LASX,UAL` turns on LASX & UAL.
   Unmentioned features turn off. With default ifunc: lasx > lsx > unaligned >
   aligned > generic, effect is: lasx > unaligned > aligned > generic; lsx off.
3. Incorrect GLIBC_TUNABLES settings will show error messages.
   For example: On lsx platforms, you cannot enable lasx features. If you do
   that, you will get error messages.
4. Valid input examples:
   - GLIBC_TUNABLES=glibc.cpu.hwcaps=LASX: lasx > aligned > generic.
   - GLIBC_TUNABLES=glibc.cpu.hwcaps=LSX,UAL: lsx > unaligned > aligned > generic.
   - GLIBC_TUNABLES=glibc.cpu.hwcaps=LASX,UAL,LASX,UAL,LSX,LASX,UAL: Repetitions
     allowed but not recommended. Results in: lasx > lsx > unaligned > aligned >
     generic.

1 files changed, 14 insertions, 4 deletions

diff --git a/sysdeps/unix/sysv/linux/loongarch/cpu-features.h b/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
index d1a280a5ee..450963cebc 100644
--- a/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
+++ b/sysdeps/unix/sysv/linux/loongarch/cpu-features.h
@@ -19,13 +19,23 @@
 #ifndef _CPU_FEATURES_LOONGARCH64_H
 #define _CPU_FEATURES_LOONGARCH64_H
 
+#include <stdint.h>
 #include <sys/auxv.h>
 
-#define SUPPORT_UAL (GLRO (dl_hwcap) & HWCAP_LOONGARCH_UAL)
-#define SUPPORT_LSX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LSX)
-#define SUPPORT_LASX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LASX)
+struct cpu_features
+ {
+    uint64_t hwcap;
+ };
 
+/* Get a pointer to the CPU features structure.  */
+extern const struct cpu_features *_dl_larch_get_cpu_features (void)
+     __attribute__ ((pure));
+
+#define SUPPORT_UAL (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_UAL)
+#define SUPPORT_LSX (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_LSX)
+#define SUPPORT_LASX (GLRO (dl_larch_cpu_features).hwcap & HWCAP_LOONGARCH_LASX)
+#define RTLD_SUPPORT_LSX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LSX)
+#define RTLD_SUPPORT_LASX (GLRO (dl_hwcap) & HWCAP_LOONGARCH_LASX)
 #define INIT_ARCH()
 
 #endif /* _CPU_FEATURES_LOONGARCH64_H  */
-