[4/5] ARM 64 bit sync atomic operations [V3]

Add ARM 64bit sync helpers for use on older ARMs.  Based on 32bit
    versions but with check for sufficiently new kernel version.

        gcc/
        * config/arm/linux-atomic-64bit.c: New (based on linux-atomic.c)
        * config/arm/linux-atomic.c: Change comment to point to 64bit version
          (SYNC_LOCK_RELEASE): Instantiate 64bit version.
        * config/arm/t-linux-eabi: Pull in linux-atomic-64bit.c

On 6 October 2011 18:54, Dr. David Alan Gilbert
<david.gilbert@linaro.org> wrote:
>    Add ARM 64bit sync helpers for use on older ARMs.  Based on 32bit
>    versions but with check for sufficiently new kernel version.
>
>        gcc/
>        * config/arm/linux-atomic-64bit.c: New (based on linux-atomic.c)
>        * config/arm/linux-atomic.c: Change comment to point to 64bit version
>          (SYNC_LOCK_RELEASE): Instantiate 64bit version.
>        * config/arm/t-linux-eabi: Pull in linux-atomic-64bit.c

OK.

Ramana
>
>
> diff --git a/gcc/config/arm/linux-atomic-64bit.c b/gcc/config/arm/linux-atomic-64bit.c
> new file mode 100644
> index 0000000..6966e66
> --- /dev/null
> +++ b/gcc/config/arm/linux-atomic-64bit.c
> @@ -0,0 +1,166 @@
> +/* 64bit Linux-specific atomic operations for ARM EABI.
> +   Copyright (C) 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
> +   Based on linux-atomic.c
> +
> +   64 bit additions david.gilbert@linaro.org
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify it under
> +the terms of the GNU General Public License as published by the Free
> +Software Foundation; either version 3, or (at your option) any later
> +version.
> +
> +GCC 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 General Public License
> +for more details.
> +
> +Under Section 7 of GPL version 3, you are granted additional
> +permissions described in the GCC Runtime Library Exception, version
> +3.1, as published by the Free Software Foundation.
> +
> +You should have received a copy of the GNU General Public License and
> +a copy of the GCC Runtime Library Exception along with this program;
> +see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
> +<http://www.gnu.org/licenses/>.  */
> +
> +/* 64bit helper functions for atomic operations; the compiler will
> +   call these when the code is compiled for a CPU without ldrexd/strexd.
> +   (If the CPU had those then the compiler inlines the operation).
> +
> +   These helpers require a kernel helper that's only present on newer
> +   kernels; we check for that in an init section and bail out rather
> +   unceremoneously.  */
> +
> +extern unsigned int __write (int fd, const void *buf, unsigned int count);
> +extern void abort (void);
> +
> +/* Kernel helper for compare-and-exchange.  */
> +typedef int (__kernel_cmpxchg64_t) (const long long* oldval,
> +                                       const long long* newval,
> +                                       long long *ptr);
> +#define __kernel_cmpxchg64 (*(__kernel_cmpxchg64_t *) 0xffff0f60)
> +
> +/* Kernel helper page version number.  */
> +#define __kernel_helper_version (*(unsigned int *)0xffff0ffc)
> +
> +/* Check that the kernel has a new enough version at load.  */
> +static void __check_for_sync8_kernelhelper (void)
> +{
> +  if (__kernel_helper_version < 5)
> +    {
> +      const char err[] = "A newer kernel is required to run this binary. "
> +                               "(__kernel_cmpxchg64 helper)\n";
> +      /* At this point we need a way to crash with some information
> +        for the user - I'm not sure I can rely on much else being
> +        available at this point, so do the same as generic-morestack.c
> +        write () and abort ().  */
> +      __write (2 /* stderr.  */, err, sizeof (err));
> +      abort ();
> +    }
> +};
> +
> +static void (*__sync8_kernelhelper_inithook[]) (void)
> +               __attribute__ ((used, section (".init_array"))) = {
> +  &__check_for_sync8_kernelhelper
> +};
> +
> +#define HIDDEN __attribute__ ((visibility ("hidden")))
> +
> +#define FETCH_AND_OP_WORD64(OP, PFX_OP, INF_OP)                        \
> +  long long HIDDEN                                             \
> +  __sync_fetch_and_##OP##_8 (long long *ptr, long long val)    \
> +  {                                                            \
> +    int failure;                                               \
> +    long long tmp,tmp2;                                                \
> +                                                               \
> +    do {                                                       \
> +      tmp = *ptr;                                              \
> +      tmp2 = PFX_OP (tmp INF_OP val);                          \
> +      failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);         \
> +    } while (failure != 0);                                    \
> +                                                               \
> +    return tmp;                                                        \
> +  }
> +
> +FETCH_AND_OP_WORD64 (add,   , +)
> +FETCH_AND_OP_WORD64 (sub,   , -)
> +FETCH_AND_OP_WORD64 (or,    , |)
> +FETCH_AND_OP_WORD64 (and,   , &)
> +FETCH_AND_OP_WORD64 (xor,   , ^)
> +FETCH_AND_OP_WORD64 (nand, ~, &)
> +
> +#define NAME_oldval(OP, WIDTH) __sync_fetch_and_##OP##_##WIDTH
> +#define NAME_newval(OP, WIDTH) __sync_##OP##_and_fetch_##WIDTH
> +
> +/* Implement both __sync_<op>_and_fetch and __sync_fetch_and_<op> for
> +   subword-sized quantities.  */
> +
> +#define OP_AND_FETCH_WORD64(OP, PFX_OP, INF_OP)                        \
> +  long long HIDDEN                                             \
> +  __sync_##OP##_and_fetch_8 (long long *ptr, long long val)    \
> +  {                                                            \
> +    int failure;                                               \
> +    long long tmp,tmp2;                                                \
> +                                                               \
> +    do {                                                       \
> +      tmp = *ptr;                                              \
> +      tmp2 = PFX_OP (tmp INF_OP val);                          \
> +      failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);         \
> +    } while (failure != 0);                                    \
> +                                                               \
> +    return tmp2;                                               \
> +  }
> +
> +OP_AND_FETCH_WORD64 (add,   , +)
> +OP_AND_FETCH_WORD64 (sub,   , -)
> +OP_AND_FETCH_WORD64 (or,    , |)
> +OP_AND_FETCH_WORD64 (and,   , &)
> +OP_AND_FETCH_WORD64 (xor,   , ^)
> +OP_AND_FETCH_WORD64 (nand, ~, &)
> +
> +long long HIDDEN
> +__sync_val_compare_and_swap_8 (long long *ptr, long long oldval,
> +                               long long newval)
> +{
> +  int failure;
> +  long long actual_oldval;
> +
> +  while (1)
> +    {
> +      actual_oldval = *ptr;
> +
> +      if (__builtin_expect (oldval != actual_oldval, 0))
> +       return actual_oldval;
> +
> +      failure = __kernel_cmpxchg64 (&actual_oldval, &newval, ptr);
> +
> +      if (__builtin_expect (!failure, 1))
> +       return oldval;
> +    }
> +}
> +
> +typedef unsigned char bool;
> +
> +bool HIDDEN
> +__sync_bool_compare_and_swap_8 (long long *ptr, long long oldval,
> +                                long long newval)
> +{
> +  int failure = __kernel_cmpxchg64 (&oldval, &newval, ptr);
> +  return (failure == 0);
> +}
> +
> +long long HIDDEN
> +__sync_lock_test_and_set_8 (long long *ptr, long long val)
> +{
> +  int failure;
> +  long long oldval;
> +
> +  do {
> +    oldval = *ptr;
> +    failure = __kernel_cmpxchg64 (&oldval, &val, ptr);
> +  } while (failure != 0);
> +
> +  return oldval;
> +}
> diff --git a/gcc/config/arm/linux-atomic.c b/gcc/config/arm/linux-atomic.c
> index 57065a6..80f161d 100644
> --- a/gcc/config/arm/linux-atomic.c
> +++ b/gcc/config/arm/linux-atomic.c
> @@ -32,8 +32,8 @@ typedef void (__kernel_dmb_t) (void);
>  #define __kernel_dmb (*(__kernel_dmb_t *) 0xffff0fa0)
>
>  /* Note: we implement byte, short and int versions of atomic operations using
> -   the above kernel helpers, but there is no support for "long long" (64-bit)
> -   operations as yet.  */
> +   the above kernel helpers; see linux-atomic-64bit.c for "long long" (64-bit)
> +   operations.  */
>
>  #define HIDDEN __attribute__ ((visibility ("hidden")))
>
> @@ -273,6 +273,7 @@ SUBWORD_TEST_AND_SET (unsigned char,  1)
>     *ptr = 0;                                                          \
>   }
>
> +SYNC_LOCK_RELEASE (long long,   8)
>  SYNC_LOCK_RELEASE (int,   4)
>  SYNC_LOCK_RELEASE (short, 2)
>  SYNC_LOCK_RELEASE (char,  1)
> diff --git a/gcc/config/arm/t-linux-eabi b/gcc/config/arm/t-linux-eabi
> index a328a00..3814cc0 100644
> --- a/gcc/config/arm/t-linux-eabi
> +++ b/gcc/config/arm/t-linux-eabi
> @@ -36,3 +36,4 @@ LIB1ASMFUNCS := $(filter-out _dvmd_tls,$(LIB1ASMFUNCS)) _dvmd_lnx _clear_cache
>  EXTRA_MULTILIB_PARTS=crtbegin.o crtend.o crtbeginS.o crtendS.o crtbeginT.o
>
>  LIB2FUNCS_STATIC_EXTRA += $(srcdir)/config/arm/linux-atomic.c
> +LIB2FUNCS_STATIC_EXTRA += $(srcdir)/config/arm/linux-atomic-64bit.c
>