bitops_arch.h

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/*
 * Copyright (C) 2000-2009 Technische Universität Dresden (Germany)
 * Copyright (C) 2016, 2022, 2024 Kernkonzept GmbH. All rights reserved.
 * Author(s): Lars Reuther <reuther@os.inf.tu-dresden.de>
 *            Torsten Frenzel <frenzel@os.inf.tu-dresden.de>
 *            Frank Mehnert <frank.mehnert@kernkonzept.com>
 *
 * License: see LICENSE.spdx (in this directory or the directories above)
 */
 
#pragma once
 
/*
 * Note: The following Assembler statement may produce wrong code:
 *   asm volatile ("btsl %1, %2" : "=@ccc"(r) : "Jr"(63), "m"(m) : "memory");
 *
 * The compiler might chose the first variant because the bit number is smaller
 * than 64. However, 'bts' is encoded as 32-bit variant ('btsl') and thus only
 * supports immediate bit values up to 31. Some assemblers support immediate
 * offsets > 31 by adapting the memory address accordingly but GAS does not.
 * With GAS, the instruction will encode an immediate value of 63 but the CPU
 * will set bit 31 instead of bit 63!
 *
 * Therefore, if we would use 'btsl' instead of 'btsq', the correct constraint
 * for the bit number parameter would be "Ir" instead of "Jr".
 */
 
__BEGIN_DECLS
 
/* set bit */
#define __L4UTIL_BITOPS_HAVE_ARCH_SET_BIT
L4_INLINE void
l4util_set_bit(int b, volatile l4_umword_t * dest)
{
  __asm__ __volatile__
    (
     "lock; btsq  %1,%0   \n\t"
     :
     :
     "m"   (*dest),   /* 0 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 1, bit number */
     :
     "memory", "cc"
     );
}
 
/* clear bit */
#define __L4UTIL_BITOPS_HAVE_ARCH_CLEAR_BIT
L4_INLINE void
l4util_clear_bit(int b, volatile l4_umword_t * dest)
{
  __asm__ __volatile__
    (
     "lock; btrq  %1,%0   \n\t"
     :
     :
     "m"   (*dest),   /* 0 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 1, bit number */
     :
     "memory", "cc"
     );
}
 
/* change bit */
#define __L4UTIL_BITOPS_HAVE_ARCH_COMPLEMENT_BIT
L4_INLINE void
l4util_complement_bit(int b, volatile l4_umword_t * dest)
{
  __asm__ __volatile__
    (
     "lock; btcq  %1,%0   \n\t"
     :
     :
     "m"   (*dest),   /* 0 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 1, bit number */
     :
     "memory", "cc"
     );
}
 
/* test bit */
#define __L4UTIL_BITOPS_HAVE_ARCH_TEST_BIT
L4_INLINE int
l4util_test_bit(int b, const volatile l4_umword_t * dest)
{
  l4_int8_t bit;
 
  __asm__ __volatile__
    (
     "btq   %2,%1   \n\t"
     :
     "=@ccc" (bit)    /* 0,     old bit value */
     :
     "m"   (*dest),   /* 1 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 2, bit number */
     :
     "memory"
     );
 
  return bit;
}
 
/* bit test and set */
#define __L4UTIL_BITOPS_HAVE_ARCH_BIT_TEST_AND_SET
L4_INLINE int
l4util_bts(int b, volatile l4_umword_t * dest)
{
  l4_int8_t bit;
 
  __asm__ __volatile__
    (
     "lock; btsq  %2,%1   \n\t"
     :
     "=@ccc" (bit)    /* 0,     old bit value */
     :
     "m"   (*dest),   /* 1 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 2, bit number */
     :
     "memory"
     );
 
  return bit;
}
 
/* bit test and reset */
#define __L4UTIL_BITOPS_HAVE_ARCH_BIT_TEST_AND_RESET
L4_INLINE int
l4util_btr(int b, volatile l4_umword_t * dest)
{
  l4_int8_t bit;
 
  __asm__ __volatile__
    (
     "lock; btrq  %2,%1   \n\t"
     :
     "=@ccc" (bit)    /* 0,     old bit value */
     :
     "m"   (*dest),   /* 1 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 2, bit number */
     :
     "memory"
     );
 
  return bit;
}
 
/* bit test and complement */
#define __L4UTIL_BITOPS_HAVE_ARCH_BIT_TEST_AND_COMPLEMENT
L4_INLINE int
l4util_btc(int b, volatile l4_umword_t * dest)
{
  l4_int8_t bit;
 
  __asm__ __volatile__
    (
     "lock; btcq  %2,%1   \n\t"
     :
     "=@ccc" (bit)    /* 0,     old bit value */
     :
     "m"   (*dest),   /* 1 mem, destination operand */
     "Jr"  ((l4_umword_t)b) /* 2, bit number */
     :
     "memory"
     );
 
  return bit;
}
 
/* bit scan reverse */
#define __L4UTIL_BITOPS_HAVE_ARCH_BIT_SCAN_REVERSE
L4_INLINE int
l4util_bsr(l4_umword_t word)
{
  l4_umword_t tmp;
 
  if (L4_UNLIKELY(word == 0))
    return -1;
 
  __asm__ __volatile__
    (
     "bsrq %1,%0 \n\t"
     :
     "=r" (tmp)       /* 0, index of most significant set bit */
     :
     "r"  (word)      /* 1, argument */
     );
 
  return tmp;
}
 
/* bit scan forward */
#define __L4UTIL_BITOPS_HAVE_ARCH_BIT_SCAN_FORWARD
L4_INLINE int
l4util_bsf(l4_umword_t word)
{
  l4_umword_t tmp;
 
  if (L4_UNLIKELY(word == 0))
    return -1;
 
  __asm__ __volatile__
    (
     "bsfq %1,%0 \n\t"
     :
     "=r" (tmp)       /* 0, index of least significant set bit */
     :
     "r"  (word)      /* 1, argument */
     );
 
  return tmp;
}
 
#define __L4UTIL_BITOPS_HAVE_ARCH_FIND_FIRST_SET_BIT
L4_INLINE int
l4util_find_first_set_bit(const void * dest, l4_size_t size)
{
  l4_mword_t dummy0, dummy1, res;
 
  __asm__ __volatile__
    (
     "repe; scasq               \n\t"
     "jz    1f                  \n\t"
     "lea  -8(%%rdi),%%rdi      \n\t"
     "bsf  (%%rdi),%%rax        \n"
     "1:                        \n\t"
     "sub  %%rbx,%%rdi          \n\t"
     "shl  $3,%%rdi             \n\t"
     "add  %%rdi,%%rax          \n\t"
     :
     "=a" (res), "=c" (dummy0), "=D" (dummy1)
     :
     "a" (0), "b" (dest), "c" ((size + 63) >> 6), "D" (dest)
     :
     "cc", "memory");
 
  return res;
}
 
#define __L4UTIL_BITOPS_HAVE_ARCH_FIND_FIRST_ZERO_BIT
L4_INLINE int
l4util_find_first_zero_bit(const void * dest, l4_size_t size)
{
  l4_mword_t dummy0, dummy1, dummy2, res;
 
  if (!size)
    return 0;
 
  __asm__ __volatile__
    (
     "repe;  scasq              \n\t"
     "je     1f                 \n\t"
     "xor   -8(%%rdi),%%rax     \n\t"
     "sub   $8,%%rdi            \n\t"
     "bsf   %%rax,%%rdx         \n"
     "1:                        \n\t"
     "sub   %%rsi,%%rdi         \n\t"
     "shl   $3,%%rdi            \n\t"
     "add   %%rdi,%%rdx         \n\t"
     :
     "=a" (dummy0), "=c" (dummy1), "=d" (res), "=D" (dummy2)
     :
     "a" (~0UL), "c" ((size + 63) >> 6), "d" (0), "D" (dest), "S" (dest)
     :
     "cc", "memory");
 
  return res;
}
 
__END_DECLS