<sys/platform/x86.h>: Remove the C preprocessor magic

In <sys/platform/x86.h>, define CPU features as enum instead of using
the C preprocessor magic to make it easier to wrap this functionality
in other languages.  Move the C preprocessor magic to internal header
for better GCC codegen when more than one features are checked in a
single expression as in x86-64 dl-hwcaps-subdirs.c.

1. Rename COMMON_CPUID_INDEX_XXX to CPUID_INDEX_XXX.
2. Move CPUID_INDEX_MAX to sysdeps/x86/include/cpu-features.h.
3. Remove struct cpu_features and __x86_get_cpu_features from
<sys/platform/x86.h>.
4. Add __x86_get_cpuid_feature_leaf to <sys/platform/x86.h> and put it
in libc.
5. Make __get_cpu_features() private to glibc.
6. Replace __x86_get_cpu_features(N) with __get_cpu_features().
7. Add _dl_x86_get_cpu_features to GLIBC_PRIVATE.
8. Use a single enum index for each CPU feature detection.
9. Pass the CPUID feature leaf to __x86_get_cpuid_feature_leaf.
10. Return zero struct cpuid_feature for the older glibc binary with a
smaller CPUID_INDEX_MAX [BZ #27104].
11. Inside glibc, use the C preprocessor magic so that cpu_features data
can be loaded just once leading to more compact code for glibc.

256 bits are used for each CPUID leaf.  Some leaves only contain a few
features.  We can add exceptions to such leaves.  But it will increase
code sizes and it is harder to provide backward/forward compatibilities
when new features are added to such leaves in the future.

When new leaves are added, _rtld_global_ro offsets will change which
leads to race condition during in-place updates. We may avoid in-place
updates by

1. Rename the old glibc.
2. Install the new glibc.
3. Remove the old glibc.

NB: A function, __x86_get_cpuid_feature_leaf , is used to avoid the copy
relocation issue with IFUNC resolver as shown in IFUNC resolver tests.

2 files changed, 1 insertions, 1 deletions

diff --git a/sysdeps/mach/hurd/i386/ld.abilist b/sysdeps/mach/hurd/i386/ld.abilist
index 751664bcda..7e20c5e7ce 100644
--- a/sysdeps/mach/hurd/i386/ld.abilist
+++ b/sysdeps/mach/hurd/i386/ld.abilist
@@ -16,4 +16,3 @@ GLIBC_2.2.6 _r_debug D 0x14
 GLIBC_2.2.6 abort F
 GLIBC_2.3 ___tls_get_addr F
 GLIBC_2.3 __tls_get_addr F
-GLIBC_2.33 __x86_get_cpu_features F
diff --git a/sysdeps/mach/hurd/i386/libc.abilist b/sysdeps/mach/hurd/i386/libc.abilist
index 7a5eb66b85..509e9b7cb0 100644
--- a/sysdeps/mach/hurd/i386/libc.abilist
+++ b/sysdeps/mach/hurd/i386/libc.abilist
@@ -2191,6 +2191,7 @@ GLIBC_2.32 thrd_current F
 GLIBC_2.32 thrd_equal F
 GLIBC_2.32 thrd_sleep F
 GLIBC_2.32 thrd_yield F
+GLIBC_2.33 __x86_get_cpuid_feature_leaf F
 GLIBC_2.33 fstat F
 GLIBC_2.33 fstat64 F
 GLIBC_2.33 fstatat F