x86: Install <sys/platform/x86.h> [BZ #26124]

Install <sys/platform/x86.h> so that programmers can do

 #if __has_include(<sys/platform/x86.h>)
 #include <sys/platform/x86.h>
 #endif
 ...

   if (CPU_FEATURE_USABLE (SSE2))
 ...
   if (CPU_FEATURE_USABLE (AVX2))
 ...

<sys/platform/x86.h> exports only:

enum
{
  COMMON_CPUID_INDEX_1 = 0,
  COMMON_CPUID_INDEX_7,
  COMMON_CPUID_INDEX_80000001,
  COMMON_CPUID_INDEX_D_ECX_1,
  COMMON_CPUID_INDEX_80000007,
  COMMON_CPUID_INDEX_80000008,
  COMMON_CPUID_INDEX_7_ECX_1,
  /* Keep the following line at the end.  */
  COMMON_CPUID_INDEX_MAX
};

struct cpuid_features
{
  struct cpuid_registers cpuid;
  struct cpuid_registers usable;
};

struct cpu_features
{
  struct cpu_features_basic basic;
  struct cpuid_features features[COMMON_CPUID_INDEX_MAX];
};

/* Get a pointer to the CPU features structure.  */
extern const struct cpu_features *__x86_get_cpu_features
  (unsigned int max) __attribute__ ((const));

Since all feature checks are done through macros, programs compiled with
a newer <sys/platform/x86.h> are compatible with the older glibc binaries
as long as the layout of struct cpu_features is identical.  The features
array can be expanded with backward binary compatibility for both .o and
.so files.  When COMMON_CPUID_INDEX_MAX is increased to support new
processor features, __x86_get_cpu_features in the older glibc binaries
returns NULL and HAS_CPU_FEATURE/CPU_FEATURE_USABLE return false on the
new processor feature.  No new symbol version is neeeded.

Both CPU_FEATURE_USABLE and HAS_CPU_FEATURE are provided.  HAS_CPU_FEATURE
can be used to identify processor features.

Note: Although GCC has __builtin_cpu_supports, it only supports a subset
of <sys/platform/x86.h> and it is equivalent to CPU_FEATURE_USABLE.  It
doesn't support HAS_CPU_FEATURE.

2 files changed, 0 insertions, 100 deletions

diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
index 395e432c09..9477538af4 100644
--- a/sysdeps/x86_64/multiarch/Makefile
+++ b/sysdeps/x86_64/multiarch/Makefile
@@ -1,7 +1,3 @@
-ifeq ($(subdir),csu)
-tests += test-multiarch
-endif
-
 ifeq ($(subdir),string)
 
 sysdep_routines += strncat-c stpncpy-c strncpy-c \
diff --git a/sysdeps/x86_64/multiarch/test-multiarch.c b/sysdeps/x86_64/multiarch/test-multiarch.c
deleted file mode 100644
index 2782803e73..0000000000
--- a/sysdeps/x86_64/multiarch/test-multiarch.c
+++ /dev/null
@@ -1,96 +0,0 @@
-/* Test CPU feature data.
-   This file is part of the GNU C Library.
-   Copyright (C) 2012-2020 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 <cpu-features.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-static char *cpu_flags;
-
-/* Search for flags in /proc/cpuinfo and store line
-   in cpu_flags.  */
-void
-get_cpuinfo (void)
-{
-  FILE *f;
-  char *line = NULL;
-  size_t len = 0;
-  ssize_t read;
-
-  f = fopen ("/proc/cpuinfo", "r");
-  if (f == NULL)
-    {
-      printf ("cannot open /proc/cpuinfo\n");
-      exit (1);
-    }
-
-  while ((read = getline (&line, &len, f)) != -1)
-    {
-      if (strncmp (line, "flags", 5) == 0)
-       {
-         cpu_flags = strdup (line);
-         break;
-       }
-    }
-  fclose (f);
-  free (line);
-}
-
-int
-check_proc (const char *proc_name, int flag, const char *name)
-{
-  int found = 0;
-
-  printf ("Checking %s:\n", name);
-  printf ("  init-arch %d\n", flag);
-  if (strstr (cpu_flags, proc_name) != NULL)
-    found = 1;
-  printf ("  cpuinfo (%s) %d\n", proc_name, found);
-
-  if (found != flag)
-    printf (" *** failure ***\n");
-
-  return (found != flag);
-}
-
-static int
-do_test (int argc, char **argv)
-{
-  int fails;
-
-  get_cpuinfo ();
-  fails = check_proc ("avx", CPU_FEATURE_USABLE (AVX),
-		      "CPU_FEATURE_USABLE (AVX)");
-  fails += check_proc ("fma4", CPU_FEATURE_USABLE (FMA4),
-		       "CPU_FEATURE_USABLE (FMA4)");
-  fails += check_proc ("sse4_2", CPU_FEATURE_USABLE (SSE4_2),
-		       "CPU_FEATURE_USABLE (SSE4_2)");
-  fails += check_proc ("sse4_1", CPU_FEATURE_USABLE (SSE4_1)
-		       , "CPU_FEATURE_USABLE (SSE4_1)");
-  fails += check_proc ("ssse3", CPU_FEATURE_USABLE (SSSE3),
-		       "CPU_FEATURE_USABLE (SSSE3)");
-  fails += check_proc ("popcnt", CPU_FEATURE_USABLE (POPCNT),
-		       "CPU_FEATURE_USABLE (POPCNT)");
-
-  printf ("%d differences between /proc/cpuinfo and glibc code.\n", fails);
-
-  return (fails != 0);
-}
-
-#include "../../../test-skeleton.c"