[thirdparty/glibc.git] / sysdeps / x86 / atomic-machine.h

/* Atomic operations.  X86 version.
   Copyright (C) 2018-2021 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
   <https://www.gnu.org/licenses/>.  */

#ifndef _X86_ATOMIC_MACHINE_H
#define _X86_ATOMIC_MACHINE_H 1

#include <stdint.h>
#include <tls.h>			/* For tcbhead_t.  */
#include <libc-pointer-arith.h>		/* For cast_to_integer.  */

typedef int8_t atomic8_t;
typedef uint8_t uatomic8_t;
typedef int_fast8_t atomic_fast8_t;
typedef uint_fast8_t uatomic_fast8_t;

typedef int16_t atomic16_t;
typedef uint16_t uatomic16_t;
typedef int_fast16_t atomic_fast16_t;
typedef uint_fast16_t uatomic_fast16_t;

typedef int32_t atomic32_t;
typedef uint32_t uatomic32_t;
typedef int_fast32_t atomic_fast32_t;
typedef uint_fast32_t uatomic_fast32_t;

typedef int64_t atomic64_t;
typedef uint64_t uatomic64_t;
typedef int_fast64_t atomic_fast64_t;
typedef uint_fast64_t uatomic_fast64_t;

typedef intptr_t atomicptr_t;
typedef uintptr_t uatomicptr_t;
typedef intmax_t atomic_max_t;
typedef uintmax_t uatomic_max_t;


#define LOCK_PREFIX "lock;"

#define USE_ATOMIC_COMPILER_BUILTINS	1

#ifdef __x86_64__
# define __HAVE_64B_ATOMICS		1
# define SP_REG				"rsp"
# define SEG_REG			"fs"
# define BR_CONSTRAINT			"q"
# define IBR_CONSTRAINT			"iq"
#else
/* Since the Pentium, i386 CPUs have supported 64-bit atomics, but the
   i386 psABI supplement provides only 4-byte alignment for uint64_t
   inside structs, so it is currently not possible to use 64-bit
   atomics on this platform.  */
# define __HAVE_64B_ATOMICS		0
# define SP_REG				"esp"
# define SEG_REG			"gs"
# define BR_CONSTRAINT			"r"
# define IBR_CONSTRAINT			"ir"
#endif
#define ATOMIC_EXCHANGE_USES_CAS	0

#define atomic_compare_and_exchange_val_acq(mem, newval, oldval) \
  __sync_val_compare_and_swap (mem, oldval, newval)
#define atomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
  (! __sync_bool_compare_and_swap (mem, oldval, newval))


#define __arch_c_compare_and_exchange_val_8_acq(mem, newval, oldval) \
  ({ __typeof (*mem) ret;						      \
     __asm __volatile ("cmpl $0, %%" SEG_REG ":%P5\n\t"			      \
		       "je 0f\n\t"					      \
		       "lock\n"						      \
		       "0:\tcmpxchgb %b2, %1"				      \
		       : "=a" (ret), "=m" (*mem)			      \
		       : BR_CONSTRAINT (newval), "m" (*mem), "0" (oldval),    \
			 "i" (offsetof (tcbhead_t, multiple_threads)));	      \
     ret; })

#define __arch_c_compare_and_exchange_val_16_acq(mem, newval, oldval) \
  ({ __typeof (*mem) ret;						      \
     __asm __volatile ("cmpl $0, %%" SEG_REG ":%P5\n\t"			      \
		       "je 0f\n\t"					      \
		       "lock\n"						      \
		       "0:\tcmpxchgw %w2, %1"				      \
		       : "=a" (ret), "=m" (*mem)			      \
		       : BR_CONSTRAINT (newval), "m" (*mem), "0" (oldval),    \
			 "i" (offsetof (tcbhead_t, multiple_threads)));	      \
     ret; })

#define __arch_c_compare_and_exchange_val_32_acq(mem, newval, oldval) \
  ({ __typeof (*mem) ret;						      \
     __asm __volatile ("cmpl $0, %%" SEG_REG ":%P5\n\t"			      \
		       "je 0f\n\t"					      \
		       "lock\n"						      \
		       "0:\tcmpxchgl %2, %1"				      \
		       : "=a" (ret), "=m" (*mem)			      \
		       : BR_CONSTRAINT (newval), "m" (*mem), "0" (oldval),    \
			 "i" (offsetof (tcbhead_t, multiple_threads)));       \
     ret; })

#ifdef __x86_64__
# define __arch_c_compare_and_exchange_val_64_acq(mem, newval, oldval) \
  ({ __typeof (*mem) ret;						      \
     __asm __volatile ("cmpl $0, %%fs:%P5\n\t"				      \
		       "je 0f\n\t"					      \
		       "lock\n"						      \
		       "0:\tcmpxchgq %q2, %1"				      \
		       : "=a" (ret), "=m" (*mem)			      \
		       : "q" ((atomic64_t) cast_to_integer (newval)),	      \
			 "m" (*mem),					      \
			 "0" ((atomic64_t) cast_to_integer (oldval)),	      \
			 "i" (offsetof (tcbhead_t, multiple_threads)));	      \
     ret; })
# define do_exchange_and_add_val_64_acq(pfx, mem, value) 0
# define do_add_val_64_acq(pfx, mem, value) do { } while (0)
#else
/* XXX We do not really need 64-bit compare-and-exchange.  At least
   not in the moment.  Using it would mean causing portability
   problems since not many other 32-bit architectures have support for
   such an operation.  So don't define any code for now.  If it is
   really going to be used the code below can be used on Intel Pentium
   and later, but NOT on i486.  */
# define __arch_c_compare_and_exchange_val_64_acq(mem, newval, oldval) \
  ({ __typeof (*mem) ret = *(mem);					      \
     __atomic_link_error ();						      \
     ret = (newval);							      \
     ret = (oldval);							      \
     ret; })

# define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval)	      \
  ({ __typeof (*mem) ret = *(mem);					      \
     __atomic_link_error ();						      \
     ret = (newval);							      \
     ret = (oldval);							      \
     ret; })

# define do_exchange_and_add_val_64_acq(pfx, mem, value) \
  ({ __typeof (value) __addval = (value);				      \
     __typeof (*mem) __result;						      \
     __typeof (mem) __memp = (mem);					      \
     __typeof (*mem) __tmpval;						      \
     __result = *__memp;						      \
     do									      \
       __tmpval = __result;						      \
     while ((__result = pfx##_compare_and_exchange_val_64_acq		      \
	     (__memp, __result + __addval, __result)) == __tmpval);	      \
     __result; })

# define do_add_val_64_acq(pfx, mem, value) \
  {									      \
    __typeof (value) __addval = (value);				      \
    __typeof (mem) __memp = (mem);					      \
    __typeof (*mem) __oldval = *__memp;					      \
    __typeof (*mem) __tmpval;						      \
    do									      \
      __tmpval = __oldval;						      \
    while ((__oldval = pfx##_compare_and_exchange_val_64_acq		      \
	    (__memp, __oldval + __addval, __oldval)) == __tmpval);	      \
  }
#endif


/* Note that we need no lock prefix.  */
#define atomic_exchange_acq(mem, newvalue) \
  ({ __typeof (*mem) result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile ("xchgb %b0, %1"				      \
			 : "=q" (result), "=m" (*mem)			      \
			 : "0" (newvalue), "m" (*mem));			      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile ("xchgw %w0, %1"				      \
			 : "=r" (result), "=m" (*mem)			      \
			 : "0" (newvalue), "m" (*mem));			      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile ("xchgl %0, %1"					      \
			 : "=r" (result), "=m" (*mem)			      \
			 : "0" (newvalue), "m" (*mem));			      \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile ("xchgq %q0, %1"				      \
			 : "=r" (result), "=m" (*mem)			      \
			 : "0" ((atomic64_t) cast_to_integer (newvalue)),     \
			   "m" (*mem));					      \
     else								      \
       {								      \
	 result = 0;							      \
	 __atomic_link_error ();					      \
       }								      \
     result; })


#define __arch_exchange_and_add_body(lock, pfx, mem, value) \
  ({ __typeof (*mem) __result;						      \
     __typeof (value) __addval = (value);				      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (lock "xaddb %b0, %1"				      \
			 : "=q" (__result), "=m" (*mem)			      \
			 : "0" (__addval), "m" (*mem),			      \
			   "i" (offsetof (tcbhead_t, multiple_threads)));     \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (lock "xaddw %w0, %1"				      \
			 : "=r" (__result), "=m" (*mem)			      \
			 : "0" (__addval), "m" (*mem),			      \
			   "i" (offsetof (tcbhead_t, multiple_threads)));     \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (lock "xaddl %0, %1"				      \
			 : "=r" (__result), "=m" (*mem)			      \
			 : "0" (__addval), "m" (*mem),			      \
			   "i" (offsetof (tcbhead_t, multiple_threads)));     \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile (lock "xaddq %q0, %1"				      \
			 : "=r" (__result), "=m" (*mem)			      \
			 : "0" ((atomic64_t) cast_to_integer (__addval)),     \
			   "m" (*mem),					      \
			   "i" (offsetof (tcbhead_t, multiple_threads)));     \
     else								      \
       __result = do_exchange_and_add_val_64_acq (pfx, (mem), __addval);      \
     __result; })

#define atomic_exchange_and_add(mem, value) \
  __sync_fetch_and_add (mem, value)

#define __arch_exchange_and_add_cprefix \
  "cmpl $0, %%" SEG_REG ":%P4\n\tje 0f\n\tlock\n0:\t"

#define catomic_exchange_and_add(mem, value) \
  __arch_exchange_and_add_body (__arch_exchange_and_add_cprefix, __arch_c,    \
				mem, value)


#define __arch_add_body(lock, pfx, apfx, mem, value) \
  do {									      \
    if (__builtin_constant_p (value) && (value) == 1)			      \
      pfx##_increment (mem);						      \
    else if (__builtin_constant_p (value) && (value) == -1)		      \
      pfx##_decrement (mem);						      \
    else if (sizeof (*mem) == 1)					      \
      __asm __volatile (lock "addb %b1, %0"				      \
			: "=m" (*mem)					      \
			: IBR_CONSTRAINT (value), "m" (*mem),		      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (lock "addw %w1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (value), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (lock "addl %1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (value), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (lock "addq %q1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" ((atomic64_t) cast_to_integer (value)),	      \
			  "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else								      \
      do_add_val_64_acq (apfx, (mem), (value));				      \
  } while (0)

# define atomic_add(mem, value) \
  __arch_add_body (LOCK_PREFIX, atomic, __arch, mem, value)

#define __arch_add_cprefix \
  "cmpl $0, %%" SEG_REG ":%P3\n\tje 0f\n\tlock\n0:\t"

#define catomic_add(mem, value) \
  __arch_add_body (__arch_add_cprefix, atomic, __arch_c, mem, value)


#define atomic_add_negative(mem, value) \
  ({ unsigned char __result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (LOCK_PREFIX "addb %b2, %0; sets %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : IBR_CONSTRAINT (value), "m" (*mem));		      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (LOCK_PREFIX "addw %w2, %0; sets %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" (value), "m" (*mem));			      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (LOCK_PREFIX "addl %2, %0; sets %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" (value), "m" (*mem));			      \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile (LOCK_PREFIX "addq %q2, %0; sets %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" ((atomic64_t) cast_to_integer (value)),	      \
			   "m" (*mem));					      \
     else								      \
       __atomic_link_error ();						      \
     __result; })


#define atomic_add_zero(mem, value) \
  ({ unsigned char __result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (LOCK_PREFIX "addb %b2, %0; setz %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : IBR_CONSTRAINT (value), "m" (*mem));		      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (LOCK_PREFIX "addw %w2, %0; setz %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" (value), "m" (*mem));			      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (LOCK_PREFIX "addl %2, %0; setz %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" (value), "m" (*mem));			      \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile (LOCK_PREFIX "addq %q2, %0; setz %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "ir" ((atomic64_t) cast_to_integer (value)),	      \
			   "m" (*mem));					      \
     else								      \
       __atomic_link_error ();					      \
     __result; })


#define __arch_increment_body(lock, pfx, mem) \
  do {									      \
    if (sizeof (*mem) == 1)						      \
      __asm __volatile (lock "incb %b0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (lock "incw %w0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (lock "incl %0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (lock "incq %q0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else								      \
      do_add_val_64_acq (pfx, mem, 1);					      \
  } while (0)

#define atomic_increment(mem) __arch_increment_body (LOCK_PREFIX, __arch, mem)

#define __arch_increment_cprefix \
  "cmpl $0, %%" SEG_REG ":%P2\n\tje 0f\n\tlock\n0:\t"

#define catomic_increment(mem) \
  __arch_increment_body (__arch_increment_cprefix, __arch_c, mem)


#define atomic_increment_and_test(mem) \
  ({ unsigned char __result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (LOCK_PREFIX "incb %b0; sete %b1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (LOCK_PREFIX "incw %w0; sete %w1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (LOCK_PREFIX "incl %0; sete %1"			      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile (LOCK_PREFIX "incq %q0; sete %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else								      \
       __atomic_link_error ();					      \
     __result; })


#define __arch_decrement_body(lock, pfx, mem) \
  do {									      \
    if (sizeof (*mem) == 1)						      \
      __asm __volatile (lock "decb %b0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (lock "decw %w0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (lock "decl %0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (lock "decq %q0"					      \
			: "=m" (*mem)					      \
			: "m" (*mem),					      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else								      \
      do_add_val_64_acq (pfx, mem, -1);					      \
  } while (0)

#define atomic_decrement(mem) __arch_decrement_body (LOCK_PREFIX, __arch, mem)

#define __arch_decrement_cprefix \
  "cmpl $0, %%" SEG_REG ":%P2\n\tje 0f\n\tlock\n0:\t"

#define catomic_decrement(mem) \
  __arch_decrement_body (__arch_decrement_cprefix, __arch_c, mem)


#define atomic_decrement_and_test(mem) \
  ({ unsigned char __result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (LOCK_PREFIX "decb %b0; sete %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (LOCK_PREFIX "decw %w0; sete %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (LOCK_PREFIX "decl %0; sete %1"			      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     else								      \
       __asm __volatile (LOCK_PREFIX "decq %q0; sete %1"		      \
			 : "=m" (*mem), "=qm" (__result)		      \
			 : "m" (*mem));					      \
     __result; })


#define atomic_bit_set(mem, bit) \
  do {									      \
    if (sizeof (*mem) == 1)						      \
      __asm __volatile (LOCK_PREFIX "orb %b2, %0"			      \
			: "=m" (*mem)					      \
			: "m" (*mem), IBR_CONSTRAINT (1L << (bit)));	      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (LOCK_PREFIX "orw %w2, %0"			      \
			: "=m" (*mem)					      \
			: "m" (*mem), "ir" (1L << (bit)));		      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (LOCK_PREFIX "orl %2, %0"			      \
			: "=m" (*mem)					      \
			: "m" (*mem), "ir" (1L << (bit)));		      \
    else if (__builtin_constant_p (bit) && (bit) < 32)			      \
      __asm __volatile (LOCK_PREFIX "orq %2, %0"			      \
			: "=m" (*mem)					      \
			: "m" (*mem), "i" (1L << (bit)));		      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (LOCK_PREFIX "orq %q2, %0"			      \
			: "=m" (*mem)					      \
			: "m" (*mem), "r" (1UL << (bit)));		      \
    else								      \
      __atomic_link_error ();						      \
  } while (0)


#define atomic_bit_test_set(mem, bit) \
  ({ unsigned char __result;						      \
     if (sizeof (*mem) == 1)						      \
       __asm __volatile (LOCK_PREFIX "btsb %3, %1; setc %0"		      \
			 : "=q" (__result), "=m" (*mem)			      \
			 : "m" (*mem), IBR_CONSTRAINT (bit));		      \
     else if (sizeof (*mem) == 2)					      \
       __asm __volatile (LOCK_PREFIX "btsw %3, %1; setc %0"		      \
			 : "=q" (__result), "=m" (*mem)			      \
			 : "m" (*mem), "ir" (bit));			      \
     else if (sizeof (*mem) == 4)					      \
       __asm __volatile (LOCK_PREFIX "btsl %3, %1; setc %0"		      \
			 : "=q" (__result), "=m" (*mem)			      \
			 : "m" (*mem), "ir" (bit));			      \
     else if (__HAVE_64B_ATOMICS)					      \
       __asm __volatile (LOCK_PREFIX "btsq %3, %1; setc %0"		      \
			 : "=q" (__result), "=m" (*mem)			      \
			 : "m" (*mem), "ir" (bit));			      \
     else							      	      \
       __atomic_link_error ();					      \
     __result; })


#define __arch_and_body(lock, mem, mask) \
  do {									      \
    if (sizeof (*mem) == 1)						      \
      __asm __volatile (lock "andb %b1, %0"				      \
			: "=m" (*mem)					      \
			: IBR_CONSTRAINT (mask), "m" (*mem),		      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (lock "andw %w1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (lock "andl %1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (lock "andq %q1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else								      \
      __atomic_link_error ();						      \
  } while (0)

#define __arch_cprefix \
  "cmpl $0, %%" SEG_REG ":%P3\n\tje 0f\n\tlock\n0:\t"

#define atomic_and(mem, mask) __arch_and_body (LOCK_PREFIX, mem, mask)

#define catomic_and(mem, mask) __arch_and_body (__arch_cprefix, mem, mask)


#define __arch_or_body(lock, mem, mask) \
  do {									      \
    if (sizeof (*mem) == 1)						      \
      __asm __volatile (lock "orb %b1, %0"				      \
			: "=m" (*mem)					      \
			: IBR_CONSTRAINT (mask), "m" (*mem),		      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 2)					      \
      __asm __volatile (lock "orw %w1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (sizeof (*mem) == 4)					      \
      __asm __volatile (lock "orl %1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else if (__HAVE_64B_ATOMICS)					      \
      __asm __volatile (lock "orq %q1, %0"				      \
			: "=m" (*mem)					      \
			: "ir" (mask), "m" (*mem),			      \
			  "i" (offsetof (tcbhead_t, multiple_threads)));      \
    else								      \
      __atomic_link_error ();						      \
  } while (0)

#define atomic_or(mem, mask) __arch_or_body (LOCK_PREFIX, mem, mask)

#define catomic_or(mem, mask) __arch_or_body (__arch_cprefix, mem, mask)

/* We don't use mfence because it is supposedly slower due to having to
   provide stronger guarantees (e.g., regarding self-modifying code).  */
#define atomic_full_barrier() \
    __asm __volatile (LOCK_PREFIX "orl $0, (%%" SP_REG ")" ::: "memory")
#define atomic_read_barrier() __asm ("" ::: "memory")
#define atomic_write_barrier() __asm ("" ::: "memory")

#define atomic_spin_nop() __asm ("pause")

#endif /* atomic-machine.h */