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.

6 files changed, 171 insertions, 4 deletions

diff --git a/sysdeps/loongarch/Makefile b/sysdeps/loongarch/Makefile
index 43d2f58..30a1f4a 100644
--- a/sysdeps/loongarch/Makefile
+++ b/sysdeps/loongarch/Makefile
@@ -6,6 +6,10 @@ ifeq ($(subdir),elf)
 gen-as-const-headers += dl-link.sym
 endif
 
+ifeq ($(subdir),elf)
+  sysdep-dl-routines += dl-get-cpu-features
+endif
+
 # LoongArch's assembler also needs to know about PIC as it changes the
 # definition of some assembler macros.
 ASFLAGS-.os += $(pic-ccflag)
diff --git a/sysdeps/loongarch/Versions b/sysdeps/loongarch/Versions
new file mode 100644
index 0000000..33ae2cc
--- /dev/null
+++ b/sysdeps/loongarch/Versions
@@ -0,0 +1,5 @@
+ld {
+  GLIBC_PRIVATE {
+    _dl_larch_get_cpu_features;
+  }
+}
diff --git a/sysdeps/loongarch/cpu-tunables.c b/sysdeps/loongarch/cpu-tunables.c
new file mode 100644
index 0000000..8e9fab9
--- /dev/null
+++ b/sysdeps/loongarch/cpu-tunables.c
@@ -0,0 +1,89 @@
+/* LoongArch CPU feature tuning.
+   This file is part of the GNU C Library.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+# include <stdbool.h>
+# include <stdint.h>
+# include <unistd.h>		/* Get STDOUT_FILENO for _dl_printf.  */
+# include <elf/dl-tunables.h>
+# include <string.h>
+# include <cpu-features.h>
+# include <ldsodefs.h>
+# include <sys/auxv.h>
+
+# define HWCAP_LOONGARCH_IFUNC \
+  (HWCAP_LOONGARCH_UAL | HWCAP_LOONGARCH_LSX | HWCAP_LOONGARCH_LASX)
+
+# define CHECK_GLIBC_IFUNC_CPU_OFF(f, name, len)			\
+  _Static_assert (sizeof (#name) - 1 == len, #name " != " #len);	\
+  if (!memcmp (f, #name, len) &&					\
+      (GLRO (dl_hwcap) & HWCAP_LOONGARCH_##name))			\
+    {									\
+      hwcap |= (HWCAP_LOONGARCH_##name | (~HWCAP_LOONGARCH_IFUNC));	\
+      break;								\
+    }									\
+
+attribute_hidden
+void
+TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
+{
+  const char *p = valp->strval;
+  size_t len;
+  unsigned long hwcap = 0;
+  const char *c;
+
+  do {
+      for (c = p; *c != ','; c++)
+	if (*c == '\0')
+	  break;
+
+      len = c - p;
+
+      switch(len)
+      {
+	default:
+	  _dl_fatal_printf (
+	    "The valid values of glibc.cpu.hwcaps is UAL, LASX, LSX!!\n"
+			    );
+	  break;
+	case 3:
+	  {
+	    CHECK_GLIBC_IFUNC_CPU_OFF (p, LSX, 3);
+	    CHECK_GLIBC_IFUNC_CPU_OFF (p, UAL, 3);
+	    _dl_fatal_printf (
+		"Some features are invalid or not supported on this machine!!\n"
+		"The valid values of glibc.cpu.hwcaps is UAL, LASX, LSX!!\n"
+                       );
+	  }
+	  break;
+	case 4:
+	  {
+	    CHECK_GLIBC_IFUNC_CPU_OFF (p, LASX, 4);
+	    _dl_fatal_printf (
+		"Some features are invalid or not supported on this machine!!\n"
+		"The valid values of glibc.cpu.hwcaps is UAL, LASX, LSX!!\n"
+                       );
+	  }
+	  break;
+      }
+
+      p += len + 1;
+    }
+  while (*c != '\0');
+
+  GLRO (dl_larch_cpu_features).hwcap &= hwcap;
+}
diff --git a/sysdeps/loongarch/dl-get-cpu-features.c b/sysdeps/loongarch/dl-get-cpu-features.c
new file mode 100644
index 0000000..7cd9bc1
--- /dev/null
+++ b/sysdeps/loongarch/dl-get-cpu-features.c
@@ -0,0 +1,25 @@
+/* Define _dl_larch_get_cpu_features.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+
+#include <ldsodefs.h>
+
+const struct cpu_features *
+_dl_larch_get_cpu_features (void)
+{
+  return &GLRO(dl_larch_cpu_features);
+}
diff --git a/sysdeps/loongarch/dl-machine.h b/sysdeps/loongarch/dl-machine.h
index 57913ce..b395a92 100644
--- a/sysdeps/loongarch/dl-machine.h
+++ b/sysdeps/loongarch/dl-machine.h
@@ -29,6 +29,8 @@
 #include <dl-static-tls.h>
 #include <dl-machine-rel.h>
 
+#include <cpu-features.c>
+
 #ifndef _RTLD_PROLOGUE
 # define _RTLD_PROLOGUE(entry)					\
 	".globl\t" __STRING (entry) "\n\t"			\
@@ -53,6 +55,23 @@
 #define ELF_MACHINE_NO_REL 1
 #define ELF_MACHINE_NO_RELA 0
 
+#define DL_PLATFORM_INIT dl_platform_init ()
+
+static inline void __attribute__ ((unused))
+dl_platform_init (void)
+{
+  if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
+    /* Avoid an empty string which would disturb us.  */
+    GLRO(dl_platform) = NULL;
+
+#ifdef SHARED
+  /* init_cpu_features has been called early from __libc_start_main in
+     static executable.  */
+  init_cpu_features (&GLRO(dl_larch_cpu_features));
+#endif
+}
+
+
 /* Return nonzero iff ELF header is compatible with the running host.  */
 static inline int
 elf_machine_matches_host (const ElfW (Ehdr) *ehdr)
@@ -290,9 +309,9 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
       if (profile != 0)
 	{
 #if !defined __loongarch_soft_float
-	  if (SUPPORT_LASX)
+	  if (RTLD_SUPPORT_LASX)
 	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_profile_lasx;
-	  else if (SUPPORT_LSX)
+	  else if (RTLD_SUPPORT_LSX)
 	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_profile_lsx;
 	  else
 #endif
@@ -310,9 +329,9 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
 	     indicated by the offset on the stack, and then jump to
 	     the resolved address.  */
 #if !defined __loongarch_soft_float
-	  if (SUPPORT_LASX)
+	  if (RTLD_SUPPORT_LASX)
 	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve_lasx;
-	  else if (SUPPORT_LSX)
+	  else if (RTLD_SUPPORT_LSX)
 	    gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve_lsx;
 	  else
 #endif
diff --git a/sysdeps/loongarch/dl-tunables.list b/sysdeps/loongarch/dl-tunables.list
new file mode 100644
index 0000000..66b3427
--- /dev/null
+++ b/sysdeps/loongarch/dl-tunables.list
@@ -0,0 +1,25 @@
+# LoongArch specific tunables.
+# Copyright (C) 2023 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+
+# The GNU C Library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <http://www.gnu.org/licenses/>.
+
+glibc {
+  cpu {
+    hwcaps {
+      type: STRING
+    }
+  }
+}