path: root/sysdeps/x86/cpu-features.c

/* Initialize CPU feature data.
   This file is part of the GNU C Library.
   Copyright (C) 2008-2023 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 <dl-hwcap.h>
#include <libc-pointer-arith.h>
#include <get-isa-level.h>
#include <cacheinfo.h>
#include <dl-cacheinfo.h>
#include <dl-minsigstacksize.h>

#if HAVE_TUNABLES
extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
  attribute_hidden;

# if CET_ENABLED
extern void TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *)
  attribute_hidden;
extern void TUNABLE_CALLBACK (set_x86_shstk) (tunable_val_t *)
  attribute_hidden;
# endif
#endif

#if CET_ENABLED
# include <dl-cet.h>
#endif

static void
update_active (struct cpu_features *cpu_features)
{
  /* Copy the cpuid bits to active bits for CPU featuress whose usability
     in user space can be detected without additonal OS support.  */
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE3);
  CPU_FEATURE_SET_ACTIVE (cpu_features, PCLMULQDQ);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSSE3);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CMPXCHG16B);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE4_1);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE4_2);
  CPU_FEATURE_SET_ACTIVE (cpu_features, MOVBE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, POPCNT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, AES);
  CPU_FEATURE_SET_ACTIVE (cpu_features, OSXSAVE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, TSC);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CX8);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CMOV);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CLFSH);
  CPU_FEATURE_SET_ACTIVE (cpu_features, MMX);
  CPU_FEATURE_SET_ACTIVE (cpu_features, FXSR);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE2);
  CPU_FEATURE_SET_ACTIVE (cpu_features, HTT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, BMI1);
  CPU_FEATURE_SET_ACTIVE (cpu_features, HLE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, BMI2);
  CPU_FEATURE_SET_ACTIVE (cpu_features, ERMS);
  CPU_FEATURE_SET_ACTIVE (cpu_features, RDSEED);
  CPU_FEATURE_SET_ACTIVE (cpu_features, ADX);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CLFLUSHOPT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CLWB);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SHA);
  CPU_FEATURE_SET_ACTIVE (cpu_features, PREFETCHWT1);
  CPU_FEATURE_SET_ACTIVE (cpu_features, OSPKE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, WAITPKG);
  CPU_FEATURE_SET_ACTIVE (cpu_features, GFNI);
  CPU_FEATURE_SET_ACTIVE (cpu_features, RDPID);
  CPU_FEATURE_SET_ACTIVE (cpu_features, RDRAND);
  CPU_FEATURE_SET_ACTIVE (cpu_features, CLDEMOTE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, MOVDIRI);
  CPU_FEATURE_SET_ACTIVE (cpu_features, MOVDIR64B);
  CPU_FEATURE_SET_ACTIVE (cpu_features, FSRM);
  CPU_FEATURE_SET_ACTIVE (cpu_features, RTM_ALWAYS_ABORT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SERIALIZE);
  CPU_FEATURE_SET_ACTIVE (cpu_features, TSXLDTRK);
  CPU_FEATURE_SET_ACTIVE (cpu_features, LAHF64_SAHF64);
  CPU_FEATURE_SET_ACTIVE (cpu_features, LZCNT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SSE4A);
  CPU_FEATURE_SET_ACTIVE (cpu_features, PREFETCHW);
  CPU_FEATURE_SET_ACTIVE (cpu_features, TBM);
  CPU_FEATURE_SET_ACTIVE (cpu_features, RDTSCP);
  CPU_FEATURE_SET_ACTIVE (cpu_features, WBNOINVD);
  CPU_FEATURE_SET_ACTIVE (cpu_features, FZLRM);
  CPU_FEATURE_SET_ACTIVE (cpu_features, FSRS);
  CPU_FEATURE_SET_ACTIVE (cpu_features, FSRCS);
  CPU_FEATURE_SET_ACTIVE (cpu_features, PTWRITE);

  if (!CPU_FEATURES_CPU_P (cpu_features, RTM_ALWAYS_ABORT))
    CPU_FEATURE_SET_ACTIVE (cpu_features, RTM);

#if CET_ENABLED
  CPU_FEATURE_SET_ACTIVE (cpu_features, IBT);
  CPU_FEATURE_SET_ACTIVE (cpu_features, SHSTK);
#endif

  /* Can we call xgetbv?  */
  if (CPU_FEATURES_CPU_P (cpu_features, OSXSAVE))
    {
      unsigned int xcrlow;
      unsigned int xcrhigh;
      asm ("xgetbv" : "=a" (xcrlow), "=d" (xcrhigh) : "c" (0));
      /* Is YMM and XMM state usable?  */
      if ((xcrlow & (bit_YMM_state | bit_XMM_state))
	  == (bit_YMM_state | bit_XMM_state))
	{
	  /* Determine if AVX is usable.  */
	  if (CPU_FEATURES_CPU_P (cpu_features, AVX))
	    {
	      CPU_FEATURE_SET (cpu_features, AVX);
	      /* The following features depend on AVX being usable.  */
	      /* Determine if AVX2 is usable.  */
	      if (CPU_FEATURES_CPU_P (cpu_features, AVX2))
		{
		  CPU_FEATURE_SET (cpu_features, AVX2);

		  /* Unaligned load with 256-bit AVX registers are faster
		     on Intel/AMD processors with AVX2.  */
		  cpu_features->preferred[index_arch_AVX_Fast_Unaligned_Load]
		    |= bit_arch_AVX_Fast_Unaligned_Load;
		}
	      /* Determine if AVX-VNNI is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, AVX_VNNI);
	      /* Determine if FMA is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, FMA);
	      /* Determine if VAES is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, VAES);
	      /* Determine if VPCLMULQDQ is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, VPCLMULQDQ);
	      /* Determine if XOP is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, XOP);
	      /* Determine if F16C is usable.  */
	      CPU_FEATURE_SET_ACTIVE (cpu_features, F16C);
	    }

	  /* Check if OPMASK state, upper 256-bit of ZMM0-ZMM15 and
	     ZMM16-ZMM31 state are enabled.  */
	  if ((xcrlow & (bit_Opmask_state | bit_ZMM0_15_state
			 | bit_ZMM16_31_state))
	      == (bit_Opmask_state | bit_ZMM0_15_state | bit_ZMM16_31_state))
	    {
	      /* Determine if AVX512F is usable.  */
	      if (CPU_FEATURES_CPU_P (cpu_features, AVX512F))
		{
		  CPU_FEATURE_SET (cpu_features, AVX512F);
		  /* Determine if AVX512CD is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512CD);
		  /* Determine if AVX512ER is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512ER);
		  /* Determine if AVX512PF is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512PF);
		  /* Determine if AVX512VL is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512VL);
		  /* Determine if AVX512DQ is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512DQ);
		  /* Determine if AVX512BW is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512BW);
		  /* Determine if AVX512_4FMAPS is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_4FMAPS);
		  /* Determine if AVX512_4VNNIW is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_4VNNIW);
		  /* Determine if AVX512_BITALG is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_BITALG);
		  /* Determine if AVX512_IFMA is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_IFMA);
		  /* Determine if AVX512_VBMI is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_VBMI);
		  /* Determine if AVX512_VBMI2 is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_VBMI2);
		  /* Determine if is AVX512_VNNI usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_VNNI);
		  /* Determine if AVX512_VPOPCNTDQ is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features,
					  AVX512_VPOPCNTDQ);
		  /* Determine if AVX512_VP2INTERSECT is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features,
					  AVX512_VP2INTERSECT);
		  /* Determine if AVX512_BF16 is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_BF16);
		  /* Determine if AVX512_FP16 is usable.  */
		  CPU_FEATURE_SET_ACTIVE (cpu_features, AVX512_FP16);
		}
	    }
	}

      /* Are XTILECFG and XTILEDATA states usable?  */
      if ((xcrlow & (bit_XTILECFG_state | bit_XTILEDATA_state))
	  == (bit_XTILECFG_state | bit_XTILEDATA_state))
	{
	  /* Determine if AMX_BF16 is usable.  */
	  CPU_FEATURE_SET_ACTIVE (cpu_features, AMX_BF16);
	  /* Determine if AMX_TILE is usable.  */
	  CPU_FEATURE_SET_ACTIVE (cpu_features, AMX_TILE);
	  /* Determine if AMX_INT8 is usable.  */
	  CPU_FEATURE_SET_ACTIVE (cpu_features, AMX_INT8);
	}

      /* These features are usable only when OSXSAVE is enabled.  */
      CPU_FEATURE_SET (cpu_features, XSAVE);
      CPU_FEATURE_SET_ACTIVE (cpu_features, XSAVEOPT);
      CPU_FEATURE_SET_ACTIVE (cpu_features, XSAVEC);
      CPU_FEATURE_SET_ACTIVE (cpu_features, XGETBV_ECX_1);
      CPU_FEATURE_SET_ACTIVE (cpu_features, XFD);

      /* For _dl_runtime_resolve, set xsave_state_size to xsave area
	 size + integer register save size and align it to 64 bytes.  */
      if (cpu_features->basic.max_cpuid >= 0xd)
	{
	  unsigned int eax, ebx, ecx, edx;

	  __cpuid_count (0xd, 0, eax, ebx, ecx, edx);
	  if (ebx != 0)
	    {
	      unsigned int xsave_state_full_size
		= ALIGN_UP (ebx + STATE_SAVE_OFFSET, 64);

	      cpu_features->xsave_state_size
		= xsave_state_full_size;
	      cpu_features->xsave_state_full_size
		= xsave_state_full_size;

	      /* Check if XSAVEC is available.  */
	      if (CPU_FEATURES_CPU_P (cpu_features, XSAVEC))
		{
		  unsigned int xstate_comp_offsets[32];
		  unsigned int xstate_comp_sizes[32];
		  unsigned int i;

		  xstate_comp_offsets[0] = 0;
		  xstate_comp_offsets[1] = 160;
		  xstate_comp_offsets[2] = 576;
		  xstate_comp_sizes[0] = 160;
		  xstate_comp_sizes[1] = 256;

		  for (i = 2; i < 32; i++)
		    {
		      if ((STATE_SAVE_MASK & (1 << i)) != 0)
			{
			  __cpuid_count (0xd, i, eax, ebx, ecx, edx);
			  xstate_comp_sizes[i] = eax;
			}
		      else
			{
			  ecx = 0;
			  xstate_comp_sizes[i] = 0;
			}

		      if (i > 2)
			{
			  xstate_comp_offsets[i]
			    = (xstate_comp_offsets[i - 1]
			       + xstate_comp_sizes[i -1]);
			  if ((ecx & (1 << 1)) != 0)
			    xstate_comp_offsets[i]
			      = ALIGN_UP (xstate_comp_offsets[i], 64);
			}
		    }

		  /* Use XSAVEC.  */
		  unsigned int size
		    = xstate_comp_offsets[31] + xstate_comp_sizes[31];
		  if (size)
		    {
		      cpu_features->xsave_state_size
			= ALIGN_UP (size + STATE_SAVE_OFFSET, 64);
		      CPU_FEATURE_SET (cpu_features, XSAVEC);
		    }
		}
	    }
	}
    }

  /* Determine if PKU is usable.  */
  if (CPU_FEATURES_CPU_P (cpu_features, OSPKE))
    CPU_FEATURE_SET (cpu_features, PKU);

  /* Determine if Key Locker instructions are usable.  */
  if (CPU_FEATURES_CPU_P (cpu_features, AESKLE))
    {
      CPU_FEATURE_SET (cpu_features, AESKLE);
      CPU_FEATURE_SET_ACTIVE (cpu_features, KL);
      CPU_FEATURE_SET_ACTIVE (cpu_features, WIDE_KL);
    }

  cpu_features->isa_1 = get_isa_level (cpu_features);
}

static void
get_extended_indices (struct cpu_features *cpu_features)
{
  unsigned int eax, ebx, ecx, edx;
  __cpuid (0x80000000, eax, ebx, ecx, edx);
  if (eax >= 0x80000001)
    __cpuid (0x80000001,
	     cpu_features->features[CPUID_INDEX_80000001].cpuid.eax,
	     cpu_features->features[CPUID_INDEX_80000001].cpuid.ebx,
	     cpu_features->features[CPUID_INDEX_80000001].cpuid.ecx,
	     cpu_features->features[CPUID_INDEX_80000001].cpuid.edx);
  if (eax >= 0x80000007)
    __cpuid (0x80000007,
	     cpu_features->features[CPUID_INDEX_80000007].cpuid.eax,
	     cpu_features->features[CPUID_INDEX_80000007].cpuid.ebx,
	     cpu_features->features[CPUID_INDEX_80000007].cpuid.ecx,
	     cpu_features->features[CPUID_INDEX_80000007].cpuid.edx);
  if (eax >= 0x80000008)
    __cpuid (0x80000008,
	     cpu_features->features[CPUID_INDEX_80000008].cpuid.eax,
	     cpu_features->features[CPUID_INDEX_80000008].cpuid.ebx,
	     cpu_features->features[CPUID_INDEX_80000008].cpuid.ecx,
	     cpu_features->features[CPUID_INDEX_80000008].cpuid.edx);
}

static void
get_common_indices (struct cpu_features *cpu_features,
		    unsigned int *family, unsigned int *model,
		    unsigned int *extended_model, unsigned int *stepping)
{
  if (family)
    {
      unsigned int eax;
      __cpuid (1, eax,
	       cpu_features->features[CPUID_INDEX_1].cpuid.ebx,
	       cpu_features->features[CPUID_INDEX_1].cpuid.ecx,
	       cpu_features->features[CPUID_INDEX_1].cpuid.edx);
      cpu_features->features[CPUID_INDEX_1].cpuid.eax = eax;
      *family = (eax >> 8) & 0x0f;
      *model = (eax >> 4) & 0x0f;
      *extended_model = (eax >> 12) & 0xf0;
      *stepping = eax & 0x0f;
      if (*family == 0x0f)
	{
	  *family += (eax >> 20) & 0xff;
	  *model += *extended_model;
	}
    }

  if (cpu_features->basic.max_cpuid >= 7)
    {
      __cpuid_count (7, 0,
		     cpu_features->features[CPUID_INDEX_7].cpuid.eax,
		     cpu_features->features[CPUID_INDEX_7].cpuid.ebx,
		     cpu_features->features[CPUID_INDEX_7].cpuid.ecx,
		     cpu_features->features[CPUID_INDEX_7].cpuid.edx);
      __cpuid_count (7, 1,
		     cpu_features->features[CPUID_INDEX_7_ECX_1].cpuid.eax,
		     cpu_features->features[CPUID_INDEX_7_ECX_1].cpuid.ebx,
		     cpu_features->features[CPUID_INDEX_7_ECX_1].cpuid.ecx,
		     cpu_features->features[CPUID_INDEX_7_ECX_1].cpuid.edx);
    }

  if (cpu_features->basic.max_cpuid >= 0xd)
    __cpuid_count (0xd, 1,
		   cpu_features->features[CPUID_INDEX_D_ECX_1].cpuid.eax,
		   cpu_features->features[CPUID_INDEX_D_ECX_1].cpuid.ebx,
		   cpu_features->features[CPUID_INDEX_D_ECX_1].cpuid.ecx,
		   cpu_features->features[CPUID_INDEX_D_ECX_1].cpuid.edx);

  if (cpu_features->basic.max_cpuid >= 0x14)
    __cpuid_count (0x14, 0,
		   cpu_features->features[CPUID_INDEX_14_ECX_0].cpuid.eax,
		   cpu_features->features[CPUID_INDEX_14_ECX_0].cpuid.ebx,
		   cpu_features->features[CPUID_INDEX_14_ECX_0].cpuid.ecx,
		   cpu_features->features[CPUID_INDEX_14_ECX_0].cpuid.edx);

  if (cpu_features->basic.max_cpuid >= 0x19)
    __cpuid_count (0x19, 0,
		   cpu_features->features[CPUID_INDEX_19].cpuid.eax,
		   cpu_features->features[CPUID_INDEX_19].cpuid.ebx,
		   cpu_features->features[CPUID_INDEX_19].cpuid.ecx,
		   cpu_features->features[CPUID_INDEX_19].cpuid.edx);

  dl_check_minsigstacksize (cpu_features);
}

_Static_assert (((index_arch_Fast_Unaligned_Load
		  == index_arch_Fast_Unaligned_Copy)
		 && (index_arch_Fast_Unaligned_Load
		     == index_arch_Prefer_PMINUB_for_stringop)
		 && (index_arch_Fast_Unaligned_Load
		     == index_arch_Slow_SSE4_2)
		 && (index_arch_Fast_Unaligned_Load
		     == index_arch_Fast_Rep_String)
		 && (index_arch_Fast_Unaligned_Load
		     == index_arch_Fast_Copy_Backward)),
		"Incorrect index_arch_Fast_Unaligned_Load");

static inline void
init_cpu_features (struct cpu_features *cpu_features)
{
  unsigned int ebx, ecx, edx;
  unsigned int family = 0;
  unsigned int model = 0;
  unsigned int stepping = 0;
  enum cpu_features_kind kind;

#if !HAS_CPUID
  if (__get_cpuid_max (0, 0) == 0)
    {
      kind = arch_kind_other;
      goto no_cpuid;
    }
#endif

  __cpuid (0, cpu_features->basic.max_cpuid, ebx, ecx, edx);

  /* This spells out "GenuineIntel".  */
  if (ebx == 0x756e6547 && ecx == 0x6c65746e && edx == 0x49656e69)
    {
      unsigned int extended_model;

      kind = arch_kind_intel;

      get_common_indices (cpu_features, &family, &model, &extended_model,
			  &stepping);

      get_extended_indices (cpu_features);

      update_active (cpu_features);

      if (family == 0x06)
	{
	  model += extended_model;
	  switch (model)
	    {
	    case 0x1c:
	    case 0x26:
	      /* BSF is slow on Atom.  */
	      cpu_features->preferred[index_arch_Slow_BSF]
		|= bit_arch_Slow_BSF;
	      break;

	    case 0x57:
	      /* Knights Landing.  Enable Silvermont optimizations.  */

	    case 0x7a:
	      /* Unaligned load versions are faster than SSSE3
		 on Goldmont Plus.  */

	    case 0x5c:
	    case 0x5f:
	      /* Unaligned load versions are faster than SSSE3
		 on Goldmont.  */

	    case 0x4c:
	    case 0x5a:
	    case 0x75:
	      /* Airmont is a die shrink of Silvermont.  */

	    case 0x37:
	    case 0x4a:
	    case 0x4d:
	    case 0x5d:
	      /* Unaligned load versions are faster than SSSE3
		 on Silvermont.  */
	      cpu_features->preferred[index_arch_Fast_Unaligned_Load]
		|= (bit_arch_Fast_Unaligned_Load
		    | bit_arch_Fast_Unaligned_Copy
		    | bit_arch_Prefer_PMINUB_for_stringop
		    | bit_arch_Slow_SSE4_2);
	      break;

	    case 0x86:
	    case 0x96:
	    case 0x9c:
	      /* Enable rep string instructions, unaligned load, unaligned
	         copy, pminub and avoid SSE 4.2 on Tremont.  */
	      cpu_features->preferred[index_arch_Fast_Rep_String]
		|= (bit_arch_Fast_Rep_String
		    | bit_arch_Fast_Unaligned_Load
		    | bit_arch_Fast_Unaligned_Copy
		    | bit_arch_Prefer_PMINUB_for_stringop
		    | bit_arch_Slow_SSE4_2);
	      break;

	    default:
	      /* Unknown family 0x06 processors.  Assuming this is one
		 of Core i3/i5/i7 processors if AVX is available.  */
	      if (!CPU_FEATURES_CPU_P (cpu_features, AVX))
		break;
	      /* Fall through.  */

	    case 0x1a:
	    case 0x1e:
	    case 0x1f:
	    case 0x25:
	    case 0x2c:
	    case 0x2e:
	    case 0x2f:
	      /* Rep string instructions, unaligned load, unaligned copy,
		 and pminub are fast on Intel Core i3, i5 and i7.  */
	      cpu_features->preferred[index_arch_Fast_Rep_String]
		|= (bit_arch_Fast_Rep_String
		    | bit_arch_Fast_Unaligned_Load
		    | bit_arch_Fast_Unaligned_Copy
		    | bit_arch_Prefer_PMINUB_for_stringop);
	      break;
	    }

	 /* Disable TSX on some processors to avoid TSX on kernels that
	    weren't updated with the latest microcode package (which
	    disables broken feature by default).  */
	 switch (model)
	    {
	    case 0x55:
	      if (stepping <= 5)
		goto disable_tsx;
	      break;
	    case 0x8e:
	      /* NB: Although the errata documents that for model == 0x8e,
		 only 0xb stepping or lower are impacted, the intention of
		 the errata was to disable TSX on all client processors on
		 all steppings.  Include 0xc stepping which is an Intel
		 Core i7-8665U, a client mobile processor.  */
	    case 0x9e:
	      if (stepping > 0xc)
		break;
	      /* Fall through.  */
	    case 0x4e:
	    case 0x5e:
	      {
		/* Disable Intel TSX and enable RTM_ALWAYS_ABORT for
		   processors listed in:

https://www.intel.com/content/www/us/en/support/articles/000059422/processors.html
		 */
disable_tsx:
		CPU_FEATURE_UNSET (cpu_features, HLE);
		CPU_FEATURE_UNSET (cpu_features, RTM);
		CPU_FEATURE_SET (cpu_features, RTM_ALWAYS_ABORT);
	      }
	      break;
	    case 0x3f:
	      /* Xeon E7 v3 with stepping >= 4 has working TSX.  */
	      if (stepping >= 4)
		break;
	      /* Fall through.  */
	    case 0x3c:
	    case 0x45:
	    case 0x46:
	      /* Disable Intel TSX on Haswell processors (except Xeon E7 v3
		 with stepping >= 4) to avoid TSX on kernels that weren't
		 updated with the latest microcode package (which disables
		 broken feature by default).  */
	      CPU_FEATURE_UNSET (cpu_features, RTM);
	      break;
	    }
	}


      /* Since AVX512ER is unique to Xeon Phi, set Prefer_No_VZEROUPPER
         if AVX512ER is available.  Don't use AVX512 to avoid lower CPU
	 frequency if AVX512ER isn't available.  */
      if (CPU_FEATURES_CPU_P (cpu_features, AVX512ER))
	cpu_features->preferred[index_arch_Prefer_No_VZEROUPPER]
	  |= bit_arch_Prefer_No_VZEROUPPER;
      else
	{
	  /* Processors with AVX512 and AVX-VNNI won't lower CPU frequency
	     when ZMM load and store instructions are used.  */
	  if (!CPU_FEATURES_CPU_P (cpu_features, AVX_VNNI))
	    cpu_features->preferred[index_arch_Prefer_No_AVX512]
	      |= bit_arch_Prefer_No_AVX512;

	  /* Avoid RTM abort triggered by VZEROUPPER inside a
	     transactionally executing RTM region.  */
	  if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
	    cpu_features->preferred[index_arch_Prefer_No_VZEROUPPER]
	      |= bit_arch_Prefer_No_VZEROUPPER;
	}

      /* Avoid avoid short distance REP MOVSB on processor with FSRM.  */
      if (CPU_FEATURES_CPU_P (cpu_features, FSRM))
	cpu_features->preferred[index_arch_Avoid_Short_Distance_REP_MOVSB]
	  |= bit_arch_Avoid_Short_Distance_REP_MOVSB;
    }
  /* This spells out "AuthenticAMD" or "HygonGenuine".  */
  else if ((ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65)
	   || (ebx == 0x6f677948 && ecx == 0x656e6975 && edx == 0x6e65476e))
    {
      unsigned int extended_model;

      kind = arch_kind_amd;

      get_common_indices (cpu_features, &family, &model, &extended_model,
			  &stepping);

      get_extended_indices (cpu_features);

      update_active (cpu_features);

      ecx = cpu_features->features[CPUID_INDEX_1].cpuid.ecx;

      if (CPU_FEATURE_USABLE_P (cpu_features, AVX))
	{
	  /* Since the FMA4 bit is in CPUID_INDEX_80000001 and
	     FMA4 requires AVX, determine if FMA4 is usable here.  */
	  CPU_FEATURE_SET_ACTIVE (cpu_features, FMA4);
	}

      if (family == 0x15)
	{
	  /* "Excavator"   */
	  if (model >= 0x60 && model <= 0x7f)
	  {
	    cpu_features->preferred[index_arch_Fast_Unaligned_Load]
	      |= (bit_arch_Fast_Unaligned_Load
		  | bit_arch_Fast_Copy_Backward);

	    /* Unaligned AVX loads are slower.*/
	    cpu_features->preferred[index_arch_AVX_Fast_Unaligned_Load]
	      &= ~bit_arch_AVX_Fast_Unaligned_Load;
	  }
	}
    }
  /* This spells out "CentaurHauls" or " Shanghai ".  */
  else if ((ebx == 0x746e6543 && ecx == 0x736c7561 && edx == 0x48727561)
	   || (ebx == 0x68532020 && ecx == 0x20206961 && edx == 0x68676e61))
    {
      unsigned int extended_model, stepping;

      kind = arch_kind_zhaoxin;

      get_common_indices (cpu_features, &family, &model, &extended_model,
			  &stepping);

      get_extended_indices (cpu_features);

      update_active (cpu_features);

      model += extended_model;
      if (family == 0x6)
        {
          if (model == 0xf || model == 0x19)
            {
	      CPU_FEATURE_UNSET (cpu_features, AVX);
	      CPU_FEATURE_UNSET (cpu_features, AVX2);

              cpu_features->preferred[index_arch_Slow_SSE4_2]
                |= bit_arch_Slow_SSE4_2;

	      cpu_features->preferred[index_arch_AVX_Fast_Unaligned_Load]
		&= ~bit_arch_AVX_Fast_Unaligned_Load;
            }
        }
      else if (family == 0x7)
        {
	  if (model == 0x1b)
	    {
	      CPU_FEATURE_UNSET (cpu_features, AVX);
	      CPU_FEATURE_UNSET (cpu_features, AVX2);

	      cpu_features->preferred[index_arch_Slow_SSE4_2]
		|= bit_arch_Slow_SSE4_2;

	      cpu_features->preferred[index_arch_AVX_Fast_Unaligned_Load]
		&= ~bit_arch_AVX_Fast_Unaligned_Load;
	    }
	  else if (model == 0x3b)
	    {
	      CPU_FEATURE_UNSET (cpu_features, AVX);
	      CPU_FEATURE_UNSET (cpu_features, AVX2);

	      cpu_features->preferred[index_arch_AVX_Fast_Unaligned_Load]
		&= ~bit_arch_AVX_Fast_Unaligned_Load;
	    }
	}
    }
  else
    {
      kind = arch_kind_other;
      get_common_indices (cpu_features, NULL, NULL, NULL, NULL);
      update_active (cpu_features);
    }

  /* Support i586 if CX8 is available.  */
  if (CPU_FEATURES_CPU_P (cpu_features, CX8))
    cpu_features->preferred[index_arch_I586] |= bit_arch_I586;

  /* Support i686 if CMOV is available.  */
  if (CPU_FEATURES_CPU_P (cpu_features, CMOV))
    cpu_features->preferred[index_arch_I686] |= bit_arch_I686;

#if !HAS_CPUID
no_cpuid:
#endif

  cpu_features->basic.kind = kind;
  cpu_features->basic.family = family;
  cpu_features->basic.model = model;
  cpu_features->basic.stepping = stepping;

  dl_init_cacheinfo (cpu_features);

#if HAVE_TUNABLES
  TUNABLE_GET (hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));

  bool disable_xsave_features = false;

  if (!CPU_FEATURE_USABLE_P (cpu_features, OSXSAVE))
    {
      /* These features are usable only if OSXSAVE is usable.  */
      CPU_FEATURE_UNSET (cpu_features, XSAVE);
      CPU_FEATURE_UNSET (cpu_features, XSAVEOPT);
      CPU_FEATURE_UNSET (cpu_features, XSAVEC);
      CPU_FEATURE_UNSET (cpu_features, XGETBV_ECX_1);
      CPU_FEATURE_UNSET (cpu_features, XFD);

      disable_xsave_features = true;
    }

  if (disable_xsave_features
      || (!CPU_FEATURE_USABLE_P (cpu_features, XSAVE)
	  && !CPU_FEATURE_USABLE_P (cpu_features, XSAVEC)))
    {
      /* Clear xsave_state_size if both XSAVE and XSAVEC aren't usable.  */
      cpu_features->xsave_state_size = 0;

      CPU_FEATURE_UNSET (cpu_features, AVX);
      CPU_FEATURE_UNSET (cpu_features, AVX2);
      CPU_FEATURE_UNSET (cpu_features, AVX_VNNI);
      CPU_FEATURE_UNSET (cpu_features, FMA);
      CPU_FEATURE_UNSET (cpu_features, VAES);
      CPU_FEATURE_UNSET (cpu_features, VPCLMULQDQ);
      CPU_FEATURE_UNSET (cpu_features, XOP);
      CPU_FEATURE_UNSET (cpu_features, F16C);
      CPU_FEATURE_UNSET (cpu_features, AVX512F);
      CPU_FEATURE_UNSET (cpu_features, AVX512CD);
      CPU_FEATURE_UNSET (cpu_features, AVX512ER);
      CPU_FEATURE_UNSET (cpu_features, AVX512PF);
      CPU_FEATURE_UNSET (cpu_features, AVX512VL);
      CPU_FEATURE_UNSET (cpu_features, AVX512DQ);
      CPU_FEATURE_UNSET (cpu_features, AVX512BW);
      CPU_FEATURE_UNSET (cpu_features, AVX512_4FMAPS);
      CPU_FEATURE_UNSET (cpu_features, AVX512_4VNNIW);
      CPU_FEATURE_UNSET (cpu_features, AVX512_BITALG);
      CPU_FEATURE_UNSET (cpu_features, AVX512_IFMA);
      CPU_FEATURE_UNSET (cpu_features, AVX512_VBMI);
      CPU_FEATURE_UNSET (cpu_features, AVX512_VBMI2);
      CPU_FEATURE_UNSET (cpu_features, AVX512_VNNI);
      CPU_FEATURE_UNSET (cpu_features, AVX512_VPOPCNTDQ);
      CPU_FEATURE_UNSET (cpu_features, AVX512_VP2INTERSECT);
      CPU_FEATURE_UNSET (cpu_features, AVX512_BF16);
      CPU_FEATURE_UNSET (cpu_features, AVX512_FP16);
      CPU_FEATURE_UNSET (cpu_features, AMX_BF16);
      CPU_FEATURE_UNSET (cpu_features, AMX_TILE);
      CPU_FEATURE_UNSET (cpu_features, AMX_INT8);

      CPU_FEATURE_UNSET (cpu_features, FMA4);
    }

#elif defined SHARED
  /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86.  The
     glibc.cpu.hwcap_mask tunable is initialized already, so no
     need to do this.  */
  GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
#endif

#ifdef __x86_64__
  GLRO(dl_hwcap) = HWCAP_X86_64;
  if (cpu_features->basic.kind == arch_kind_intel)
    {
      const char *platform = NULL;

      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512CD))
	{
	  if (CPU_FEATURE_USABLE_P (cpu_features, AVX512ER))
	    {
	      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512PF))
		platform = "xeon_phi";
	    }
	  else
	    {
	      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
		  && CPU_FEATURE_USABLE_P (cpu_features, AVX512DQ)
		  && CPU_FEATURE_USABLE_P (cpu_features, AVX512VL))
		GLRO(dl_hwcap) |= HWCAP_X86_AVX512_1;
	    }
	}

      if (platform == NULL
	  && CPU_FEATURE_USABLE_P (cpu_features, AVX2)
	  && CPU_FEATURE_USABLE_P (cpu_features, FMA)
	  && CPU_FEATURE_USABLE_P (cpu_features, BMI1)
	  && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
	  && CPU_FEATURE_USABLE_P (cpu_features, LZCNT)
	  && CPU_FEATURE_USABLE_P (cpu_features, MOVBE)
	  && CPU_FEATURE_USABLE_P (cpu_features, POPCNT))
	platform = "haswell";

      if (platform != NULL)
	GLRO(dl_platform) = platform;
    }
#else
  GLRO(dl_hwcap) = 0;
  if (CPU_FEATURE_USABLE_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

#if CET_ENABLED
# if HAVE_TUNABLES
  TUNABLE_GET (x86_ibt, tunable_val_t *,
	       TUNABLE_CALLBACK (set_x86_ibt));
  TUNABLE_GET (x86_shstk, tunable_val_t *,
	       TUNABLE_CALLBACK (set_x86_shstk));
# endif

  /* Check CET status.  */
  unsigned int cet_status = get_cet_status ();

  if ((cet_status & GNU_PROPERTY_X86_FEATURE_1_IBT) == 0)
    CPU_FEATURE_UNSET (cpu_features, IBT)
  if ((cet_status & GNU_PROPERTY_X86_FEATURE_1_SHSTK) == 0)
    CPU_FEATURE_UNSET (cpu_features, SHSTK)

  if (cet_status)
    {
      GL(dl_x86_feature_1) = cet_status;

# ifndef SHARED
      /* Check if IBT and SHSTK are enabled by kernel.  */
      if ((cet_status & GNU_PROPERTY_X86_FEATURE_1_IBT)
	  || (cet_status & GNU_PROPERTY_X86_FEATURE_1_SHSTK))
	{
	  /* Disable IBT and/or SHSTK if they are enabled by kernel, but
	     disabled by environment variable:

	     GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
	   */
	  unsigned int cet_feature = 0;
	  if (!CPU_FEATURE_USABLE (IBT))
	    cet_feature |= GNU_PROPERTY_X86_FEATURE_1_IBT;
	  if (!CPU_FEATURE_USABLE (SHSTK))
	    cet_feature |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;

	  if (cet_feature)
	    {
	      int res = dl_cet_disable_cet (cet_feature);

	      /* Clear the disabled bits in dl_x86_feature_1.  */
	      if (res == 0)
		GL(dl_x86_feature_1) &= ~cet_feature;
	    }

	  /* Lock CET if IBT or SHSTK is enabled in executable.  Don't
	     lock CET if IBT or SHSTK is enabled permissively.  */
	  if (GL(dl_x86_feature_control).ibt != cet_permissive
	      && GL(dl_x86_feature_control).shstk != cet_permissive)
	    dl_cet_lock_cet ();
	}
# endif
    }
#endif

#ifndef SHARED
  /* NB: In libc.a, call init_cacheinfo.  */
  init_cacheinfo ();
#endif
}