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Re: [PATCH] [BZ #21391] x86: Set dl_platform and dl_hwcap from CPU features

From: "Rodriguez Bahena, Victor" <victor dot rodriguez dot bahena at intel dot com>
To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
Date: Wed, 19 Apr 2017 21:11:33 +0000
Subject: Re: [PATCH] [BZ #21391] x86: Set dl_platform and dl_hwcap from CPU features
Authentication-results: sourceware.org; auth=none
References: <20170419183532.GA18407@intel.com>
-----Original Message-----
From: <libc-alpha-owner@sourceware.org> on behalf of "H.J. Lu"
<hongjiu.lu@intel.com>
Reply-To: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wednesday, April 19, 2017 at 1:35 PM
To: GNU C Library <libc-alpha@sourceware.org>
Subject: [PATCH] [BZ #21391] x86: Set dl_platform and dl_hwcap from CPU
features

>dl_platform and dl_hwcap are set from AT_PLATFORM and AT_HWCAP very
>early during startup.  They are used by dynamic linker to determine
>platform and build an array of hardware capability names, which are
>added to search path when loading shared object.  dl_platform and
>dl_hwcap are unused on x86-64.  On i386, i386, i486, i586 and i686
>platforms were supported and only SSE2 capability was used.
>
>On x86, usage of AT_PLATFORM and AT_HWCAP to determine platform and
>processor capabilities is obsolete since all information is available
>in dl_x86_cpu_features.  This patch sets dl_platform and dl_hwcap from
>dl_x86_cpu_features in dynamic linker.  On i386, the available plaforms
>are changed to i586 and i686 since i386 has been deprecated.  On x86-64,
>the available plaforms are haswell, which is for Haswell class processors
>with BMI1, BMI2, LZCNT, MOVBE, POPCNT, AVX2 and FMA, and xeon_phi, which
>is for Xeon Phi class processors with AVX512F, AVX512CD, AVX512ER and
>AVX512PF.  A capability, avx512_1, is also added to x86-64 for AVX512
>ISAs: AVX512F, AVX512CD, AVX512BW, AVX512DQ and AVX512VL.
>
>Any comments?

Tested , it works just fine

+1

Thanks for the patch

>
>H.J.
>---
>	[BZ #21391]
>	* sysdeps/i386/dl-machine.h (dl_platform_init) [IS_IN (rtld)]:
>	Only call init_cpu_features.
>	[!IS_IN (rtld)]: Only set GLRO(dl_platform) to NULL if needed.
>	* sysdeps/x86_64/dl-machine.h (dl_platform_init): Likewise.
>	* sysdeps/i386/dl-procinfo.h: Removed.
>	* sysdeps/unix/sysv/linux/i386/dl-procinfo.h: Don't include
>	<sysdeps/i386/dl-procinfo.h> nor <ldsodefs.h>.  Include
>	<sysdeps/x86/dl-procinfo.h>.
>	(_dl_procinfo): Replace _DL_HWCAP_COUNT with 32.
>	* sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h [!IS_IN (ldconfig)]:
>	Include <sysdeps/x86/dl-procinfo.h> instead of
>	 <sysdeps/generic/dl-procinfo.h>.
>	* sysdeps/x86/cpu-features.c: Include <dl-hwcap.h>.
>	(init_cpu_features): Set dl_platform, dl_hwcap and dl_hwcap_mask.
>	* sysdeps/x86/cpu-features.h (bit_cpu_LZCNT): New.
>	(bit_cpu_MOVBE): Likewise.
>	(bit_cpu_BMI1): Likewise.
>	(bit_cpu_BMI2): Likewise.
>	(index_cpu_BMI1): Likewise.
>	(index_cpu_BMI2): Likewise.
>	(index_cpu_LZCNT): Likewise.
>	(index_cpu_MOVBE): Likewise.
>	(index_cpu_POPCNT): Likewise.
>	(reg_BMI1): Likewise.
>	(reg_BMI2): Likewise.
>	(reg_LZCNT): Likewise.
>	(reg_MOVBE): Likewise.
>	(reg_POPCNT): Likewise.
>	* sysdeps/x86/dl-hwcap.h: New file.
>	* sysdeps/x86/dl-procinfo.h: Likewise.
>	* sysdeps/x86/dl-procinfo.c (_dl_x86_hwcap_flags): New.
>	(_dl_x86_platforms): Likewise.
>---
> sysdeps/i386/dl-machine.h                    |  10 +--
> sysdeps/i386/dl-procinfo.c                   |  21 +-----
> sysdeps/i386/dl-procinfo.h                   | 102
>---------------------------
> sysdeps/unix/sysv/linux/i386/dl-procinfo.h   |   6 +-
> sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h |   2 +-
> sysdeps/x86/cpu-features.c                   |  48 +++++++++++++
> sysdeps/x86/cpu-features.h                   |  15 ++++
> sysdeps/x86/dl-hwcap.h                       |  75 ++++++++++++++++++++
> sysdeps/x86/dl-procinfo.c                    |  38 +++++++++-
> sysdeps/x86/dl-procinfo.h                    |  48 +++++++++++++
> sysdeps/x86_64/dl-machine.h                  |  10 +--
> 11 files changed, 237 insertions(+), 138 deletions(-)
> delete mode 100644 sysdeps/i386/dl-procinfo.h
> create mode 100644 sysdeps/x86/dl-hwcap.h
> create mode 100644 sysdeps/x86/dl-procinfo.h
>
>diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
>index 99a72f6..57d4a0b 100644
>--- a/sysdeps/i386/dl-machine.h
>+++ b/sysdeps/i386/dl-machine.h
>@@ -233,14 +233,14 @@ _dl_start_user:\n\
> 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
>+#if IS_IN (rtld)
>   /* init_cpu_features has been called early from __libc_start_main in
>      static executable.  */
>   init_cpu_features (&GLRO(dl_x86_cpu_features));
>+#else
>+  if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
>+    /* Avoid an empty string which would disturb us.  */
>+    GLRO(dl_platform) = NULL;
> #endif
> }
> 
>diff --git a/sysdeps/i386/dl-procinfo.c b/sysdeps/i386/dl-procinfo.c
>index b832830..7237f77 100644
>--- a/sysdeps/i386/dl-procinfo.c
>+++ b/sysdeps/i386/dl-procinfo.c
>@@ -17,10 +17,7 @@
>    License along with the GNU C Library; if not, see
>    <http://www.gnu.org/licenses/>.  */
> 
>-/* This information must be kept in sync with the _DL_HWCAP_COUNT and
>-   _DL_PLATFORM_COUNT definitions in procinfo.h.
>-
>-   If anything should be added here check whether the size of each string
>+/* If anything should be added here check whether the size of each string
>    is still ok with the given array size.
> 
>    All the #ifdefs in the definitions are quite irritating but
>@@ -64,21 +61,5 @@ PROCINFO_CLASS const char _dl_x86_cap_flags[32][8]
> ,
> #endif
> 
>-#if !defined PROCINFO_DECL && defined SHARED
>-  ._dl_x86_platforms
>-#else
>-PROCINFO_CLASS const char _dl_x86_platforms[4][5]
>-#endif
>-#ifndef PROCINFO_DECL
>-= {
>-    "i386", "i486", "i586", "i686"
>-  }
>-#endif
>-#if !defined SHARED || defined PROCINFO_DECL
>-;
>-#else
>-,
>-#endif
>-
> #undef PROCINFO_DECL
> #undef PROCINFO_CLASS
>diff --git a/sysdeps/i386/dl-procinfo.h b/sysdeps/i386/dl-procinfo.h
>deleted file mode 100644
>index 9c38846..0000000
>--- a/sysdeps/i386/dl-procinfo.h
>+++ /dev/null
>@@ -1,102 +0,0 @@
>-/* i386 version of processor capability information handling macros.
>-   Copyright (C) 1998-2017 Free Software Foundation, Inc.
>-   This file is part of the GNU C Library.
>-   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
>-
>-   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/>.  */
>-
>-#ifndef _DL_PROCINFO_H
>-#define _DL_PROCINFO_H	1
>-#include <ldsodefs.h>
>-
>-#define _DL_HWCAP_COUNT 32
>-
>-#define _DL_PLATFORMS_COUNT	4
>-
>-/* Start at 48 to reserve some space.  */
>-#define _DL_FIRST_PLATFORM	48
>-/* Mask to filter out platforms.  */
>-#define _DL_HWCAP_PLATFORM	(((1ULL << _DL_PLATFORMS_COUNT) - 1) \
>-				 << _DL_FIRST_PLATFORM)
>-
>-enum
>-{
>-  HWCAP_I386_FPU   = 1 << 0,
>-  HWCAP_I386_VME   = 1 << 1,
>-  HWCAP_I386_DE    = 1 << 2,
>-  HWCAP_I386_PSE   = 1 << 3,
>-  HWCAP_I386_TSC   = 1 << 4,
>-  HWCAP_I386_MSR   = 1 << 5,
>-  HWCAP_I386_PAE   = 1 << 6,
>-  HWCAP_I386_MCE   = 1 << 7,
>-  HWCAP_I386_CX8   = 1 << 8,
>-  HWCAP_I386_APIC  = 1 << 9,
>-  HWCAP_I386_SEP   = 1 << 11,
>-  HWCAP_I386_MTRR  = 1 << 12,
>-  HWCAP_I386_PGE   = 1 << 13,
>-  HWCAP_I386_MCA   = 1 << 14,
>-  HWCAP_I386_CMOV  = 1 << 15,
>-  HWCAP_I386_FCMOV = 1 << 16,
>-  HWCAP_I386_MMX   = 1 << 23,
>-  HWCAP_I386_OSFXSR = 1 << 24,
>-  HWCAP_I386_XMM   = 1 << 25,
>-  HWCAP_I386_XMM2  = 1 << 26,
>-  HWCAP_I386_AMD3D = 1 << 31,
>-
>-  /* XXX Which others to add here?  */
>-  HWCAP_IMPORTANT = (HWCAP_I386_XMM2)
>-
>-};
>-
>-/* We cannot provide a general printing function.  */
>-#define _dl_procinfo(type, word) -1
>-
>-static inline const char *
>-__attribute__ ((unused))
>-_dl_hwcap_string (int idx)
>-{
>-  return GLRO(dl_x86_cap_flags)[idx];
>-};
>-
>-static inline int
>-__attribute__ ((unused, always_inline))
>-_dl_string_hwcap (const char *str)
>-{
>-  int i;
>-
>-  for (i = 0; i < _DL_HWCAP_COUNT; i++)
>-    {
>-      if (strcmp (str, GLRO(dl_x86_cap_flags)[i]) == 0)
>-	return i;
>-    }
>-  return -1;
>-};
>-
>-static inline int
>-__attribute__ ((unused, always_inline))
>-_dl_string_platform (const char *str)
>-{
>-  int i;
>-
>-  if (str != NULL)
>-    for (i = 0; i < _DL_PLATFORMS_COUNT; ++i)
>-      {
>-	if (strcmp (str, GLRO(dl_x86_platforms)[i]) == 0)
>-	  return _DL_FIRST_PLATFORM + i;
>-      }
>-  return -1;
>-};
>-
>-#endif /* dl-procinfo.h */
>diff --git a/sysdeps/unix/sysv/linux/i386/dl-procinfo.h
>b/sysdeps/unix/sysv/linux/i386/dl-procinfo.h
>index d49638c..a3a5f9d 100644
>--- a/sysdeps/unix/sysv/linux/i386/dl-procinfo.h
>+++ b/sysdeps/unix/sysv/linux/i386/dl-procinfo.h
>@@ -17,9 +17,7 @@
>    License along with the GNU C Library; if not, see
>    <http://www.gnu.org/licenses/>.  */
> 
>-#include <sysdeps/i386/dl-procinfo.h>
>-#include <ldsodefs.h>
>-
>+#include <sysdeps/x86/dl-procinfo.h>
> 
> #undef _dl_procinfo
> static inline int
>@@ -36,7 +34,7 @@ _dl_procinfo (unsigned int type, unsigned long int word)
> 
>   _dl_printf ("AT_HWCAP:   ");
> 
>-  for (i = 0; i < _DL_HWCAP_COUNT; ++i)
>+  for (i = 0; i < 32; ++i)
>     if (word & (1 << i))
>       _dl_printf (" %s", GLRO(dl_x86_cap_flags)[i]);
> 
>diff --git a/sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h
>b/sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h
>index 7829e1c..7b45fe4 100644
>--- a/sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h
>+++ b/sysdeps/unix/sysv/linux/x86_64/dl-procinfo.h
>@@ -1,5 +1,5 @@
> #if IS_IN (ldconfig)
> # include <sysdeps/unix/sysv/linux/i386/dl-procinfo.h>
> #else
>-# include <sysdeps/generic/dl-procinfo.h>
>+# include <sysdeps/x86/dl-procinfo.h>
> #endif
>diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
>index f30918d..b481f50 100644
>--- a/sysdeps/x86/cpu-features.c
>+++ b/sysdeps/x86/cpu-features.c
>@@ -18,6 +18,7 @@
> 
> #include <cpuid.h>
> #include <cpu-features.h>
>+#include <dl-hwcap.h>
> 
> static void
> get_common_indeces (struct cpu_features *cpu_features,
>@@ -310,4 +311,51 @@ no_cpuid:
>   cpu_features->family = family;
>   cpu_features->model = model;
>   cpu_features->kind = kind;
>+
>+#if IS_IN (rtld)
>+  /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86.  */
>+  GLRO(dl_platform) = NULL;
>+  GLRO(dl_hwcap) = 0;
>+  GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
>+
>+# ifdef __x86_64__
>+  if (cpu_features->kind == arch_kind_intel)
>+    {
>+      if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
>+	  && CPU_FEATURES_CPU_P (cpu_features, AVX512CD))
>+	{
>+	  if (CPU_FEATURES_CPU_P (cpu_features, AVX512ER))
>+	    {
>+	      if (CPU_FEATURES_CPU_P (cpu_features, AVX512PF))
>+		GLRO(dl_platform) = "xeon_phi";
>+	    }
>+	  else
>+	    {
>+	      if (CPU_FEATURES_CPU_P (cpu_features, AVX512BW)
>+		  && CPU_FEATURES_CPU_P (cpu_features, AVX512DQ)
>+		  && CPU_FEATURES_CPU_P (cpu_features, AVX512VL))
>+		GLRO(dl_hwcap) |= HWCAP_X86_AVX512_1;
>+	    }
>+	}
>+
>+      if (GLRO(dl_platform) == NULL
>+	  && CPU_FEATURES_ARCH_P (cpu_features, AVX2_Usable)
>+	  && CPU_FEATURES_ARCH_P (cpu_features, FMA_Usable)
>+	  && CPU_FEATURES_CPU_P (cpu_features, BMI1)
>+	  && CPU_FEATURES_CPU_P (cpu_features, BMI2)
>+	  && CPU_FEATURES_CPU_P (cpu_features, LZCNT)
>+	  && CPU_FEATURES_CPU_P (cpu_features, MOVBE)
>+	  && CPU_FEATURES_CPU_P (cpu_features, POPCNT))
>+	GLRO(dl_platform) = "haswell";
>+    }
>+# else
>+  if (CPU_FEATURES_CPU_P (cpu_features, SSE2))
>+    GLRO(dl_hwcap) |= HWCAP_X86_SSE2;
>+
>+  if (CPU_FEATURES_ARCH_P (cpu_features, I686))
>+    GLRO(dl_platform) = "i686";
>+  else if (CPU_FEATURES_ARCH_P (cpu_features, I586))
>+    GLRO(dl_platform) = "i586";
>+# endif
>+#endif
> }
>diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
>index 85a39e7..31c7c80 100644
>--- a/sysdeps/x86/cpu-features.h
>+++ b/sysdeps/x86/cpu-features.h
>@@ -57,8 +57,13 @@
> #define bit_cpu_FMA		(1 << 12)
> #define bit_cpu_FMA4		(1 << 16)
> #define bit_cpu_HTT		(1 << 28)
>+#define bit_cpu_LZCNT		(1 << 5)
>+#define bit_cpu_MOVBE		(1 << 22)
>+#define bit_cpu_POPCNT		(1 << 23)
> 
> /* COMMON_CPUID_INDEX_7.  */
>+#define bit_cpu_BMI1		(1 << 3)
>+#define bit_cpu_BMI2		(1 << 8)
> #define bit_cpu_ERMS		(1 << 9)
> #define bit_cpu_RTM		(1 << 11)
> #define bit_cpu_AVX2		(1 << 5)
>@@ -258,6 +263,11 @@ extern const struct cpu_features *__get_cpu_features
>(void)
> # define index_cpu_POPCOUNT	COMMON_CPUID_INDEX_1
> # define index_cpu_OSXSAVE	COMMON_CPUID_INDEX_1
> # define index_cpu_HTT		COMMON_CPUID_INDEX_1
>+# define index_cpu_BMI1		COMMON_CPUID_INDEX_7
>+# define index_cpu_BMI2		COMMON_CPUID_INDEX_7
>+# define index_cpu_LZCNT	COMMON_CPUID_INDEX_1
>+# define index_cpu_MOVBE	COMMON_CPUID_INDEX_1
>+# define index_cpu_POPCNT	COMMON_CPUID_INDEX_1
> 
> # define reg_CX8		edx
> # define reg_CMOV		edx
>@@ -282,6 +292,11 @@ extern const struct cpu_features *__get_cpu_features
>(void)
> # define reg_POPCOUNT		ecx
> # define reg_OSXSAVE		ecx
> # define reg_HTT		edx
>+# define reg_BMI1		ebx
>+# define reg_BMI2		ebx
>+# define reg_LZCNT		ecx
>+# define reg_MOVBE		ecx
>+# define reg_POPCNT		ecx
> 
> # define index_arch_Fast_Rep_String	FEATURE_INDEX_1
> # define index_arch_Fast_Copy_Backward	FEATURE_INDEX_1
>diff --git a/sysdeps/x86/dl-hwcap.h b/sysdeps/x86/dl-hwcap.h
>new file mode 100644
>index 0000000..c956684
>--- /dev/null
>+++ b/sysdeps/x86/dl-hwcap.h
>@@ -0,0 +1,75 @@
>+/* x86 version of hardware capability information handling macros.
>+   Copyright (C) 2017 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/>.  */
>+
>+#ifndef _DL_HWCAP_H
>+#define _DL_HWCAP_H
>+
>+#if IS_IN (ldconfig)
>+/* Since ldconfig processes both i386 and x86-64 libraries, it needs
>+   to cover all platforms and hardware capabilities.  */
>+# define HWCAP_PLATFORMS_START	0
>+# define HWCAP_PLATFORMS_COUNT	4
>+# define HWCAP_START		0
>+# define HWCAP_COUNT		2
>+# define HWCAP_IMPORTANT	(HWCAP_X86_SSE2 | HWCAP_X86_AVX512_1)
>+#elif defined __x86_64__
>+/* For 64 bit, only cover x86-64 platforms and capabilities.  */
>+# define HWCAP_PLATFORMS_START	2
>+# define HWCAP_PLATFORMS_COUNT	4
>+# define HWCAP_START		1
>+# define HWCAP_COUNT		2
>+# define HWCAP_IMPORTANT	(HWCAP_X86_AVX512_1)
>+#else
>+/* For 32 bit, only cover i586, i686 and SSE2.  */
>+# define HWCAP_PLATFORMS_START	0
>+# define HWCAP_PLATFORMS_COUNT	2
>+# define HWCAP_START		0
>+# define HWCAP_COUNT		1
>+# define HWCAP_IMPORTANT	(HWCAP_X86_SSE2)
>+#endif
>+
>+enum
>+{
>+  HWCAP_X86_SSE2		= 1 << 0,
>+  HWCAP_X86_AVX512_1		= 1 << 1
>+};
>+
>+static inline const char *
>+__attribute__ ((unused))
>+_dl_hwcap_string (int idx)
>+{
>+  return GLRO(dl_x86_hwcap_flags)[idx];
>+};
>+
>+static inline int
>+__attribute__ ((unused, always_inline))
>+_dl_string_hwcap (const char *str)
>+{
>+  int i;
>+
>+  for (i = HWCAP_START; i < HWCAP_COUNT; i++)
>+    {
>+      if (strcmp (str, GLRO(dl_x86_hwcap_flags)[i]) == 0)
>+	return i;
>+    }
>+  return -1;
>+};
>+
>+/* We cannot provide a general printing function.  */
>+#define _dl_procinfo(type, word) -1
>+
>+#endif /* dl-hwcap.h */
>diff --git a/sysdeps/x86/dl-procinfo.c b/sysdeps/x86/dl-procinfo.c
>index 9d154bf..43ab8fe 100644
>--- a/sysdeps/x86/dl-procinfo.c
>+++ b/sysdeps/x86/dl-procinfo.c
>@@ -16,7 +16,11 @@
>    License along with the GNU C Library; if not, see
>    <http://www.gnu.org/licenses/>.  */
> 
>-/* If anything should be added here check whether the size of each string
>+/* This information must be kept in sync with the _DL_HWCAP_COUNT,
>+   HWCAP_PLATFORMS_START and HWCAP_PLATFORMS_COUNT definitions in
>+   dl-hwcap.h.
>+
>+   If anything should be added here check whether the size of each string
>    is still ok with the given array size.
> 
>    All the #ifdefs in the definitions are quite irritating but
>@@ -50,3 +54,35 @@ PROCINFO_CLASS struct cpu_features _dl_x86_cpu_features
> ,
> # endif
> #endif
>+
>+#if !defined PROCINFO_DECL && defined SHARED
>+  ._dl_x86_hwcap_flags
>+#else
>+PROCINFO_CLASS const char _dl_x86_hwcap_flags[2][9]
>+#endif
>+#ifndef PROCINFO_DECL
>+= {
>+    "sse2", "avx512_1"
>+  }
>+#endif
>+#if !defined SHARED || defined PROCINFO_DECL
>+;
>+#else
>+,
>+#endif
>+
>+#if !defined PROCINFO_DECL && defined SHARED
>+  ._dl_x86_platforms
>+#else
>+PROCINFO_CLASS const char _dl_x86_platforms[4][9]
>+#endif
>+#ifndef PROCINFO_DECL
>+= {
>+    "i586", "i686", "haswell", "xeon_phi"
>+  }
>+#endif
>+#if !defined SHARED || defined PROCINFO_DECL
>+;
>+#else
>+,
>+#endif
>diff --git a/sysdeps/x86/dl-procinfo.h b/sysdeps/x86/dl-procinfo.h
>new file mode 100644
>index 0000000..5feb146
>--- /dev/null
>+++ b/sysdeps/x86/dl-procinfo.h
>@@ -0,0 +1,48 @@
>+/* x86 version of processor capability information handling macros.
>+   Copyright (C) 2017 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/>.  */
>+
>+#ifndef _DL_PROCINFO_H
>+#define _DL_PROCINFO_H	1
>+#include <ldsodefs.h>
>+#include <dl-hwcap.h>
>+
>+#define _DL_HWCAP_COUNT		HWCAP_COUNT
>+#define _DL_PLATFORMS_COUNT	HWCAP_PLATFORMS_COUNT
>+
>+/* Start at 48 to reserve spaces for hardware capabilities.  */
>+#define _DL_FIRST_PLATFORM	48
>+/* Mask to filter out platforms.  */
>+#define _DL_HWCAP_PLATFORM	(((1ULL << _DL_PLATFORMS_COUNT) - 1) \
>+				 << _DL_FIRST_PLATFORM)
>+
>+static inline int
>+__attribute__ ((unused, always_inline))
>+_dl_string_platform (const char *str)
>+{
>+  int i;
>+
>+  if (str != NULL)
>+    for (i = HWCAP_PLATFORMS_START; i < HWCAP_PLATFORMS_COUNT; ++i)
>+      {
>+	if (strcmp (str, GLRO(dl_x86_platforms)[i]) == 0)
>+	  return _DL_FIRST_PLATFORM + i;
>+      }
>+  return -1;
>+};
>+
>+#endif /* dl-procinfo.h */
>diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
>index daf4d8c..0015db4 100644
>--- a/sysdeps/x86_64/dl-machine.h
>+++ b/sysdeps/x86_64/dl-machine.h
>@@ -240,14 +240,14 @@ _dl_start_user:\n\
> 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
>+#if IS_IN (rtld)
>   /* init_cpu_features has been called early from __libc_start_main in
>      static executable.  */
>   init_cpu_features (&GLRO(dl_x86_cpu_features));
>+#else
>+  if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
>+    /* Avoid an empty string which would disturb us.  */
>+    GLRO(dl_platform) = NULL;
> #endif
> }
> 
>-- 
>2.9.3
>
References:
- [PATCH] [BZ #21391] x86: Set dl_platform and dl_hwcap from CPU features
  - From: H.J. Lu
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