1  /* Copyright (C) 2012-2023 Free Software Foundation, Inc.
       2     Contributed by Richard Henderson <rth@redhat.com>.
       3  
       4     This file is part of the GNU Atomic Library (libatomic).
       5  
       6     Libatomic is free software; you can redistribute it and/or modify it
       7     under the terms of the GNU General Public License as published by
       8     the Free Software Foundation; either version 3 of the License, or
       9     (at your option) any later version.
      10  
      11     Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
      12     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
      13     FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
      14     more details.
      15  
      16     Under Section 7 of GPL version 3, you are granted additional
      17     permissions described in the GCC Runtime Library Exception, version
      18     3.1, as published by the Free Software Foundation.
      19  
      20     You should have received a copy of the GNU General Public License and
      21     a copy of the GCC Runtime Library Exception along with this program;
      22     see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      23     <http://www.gnu.org/licenses/>.  */
      24  
      25  #include "libatomic_i.h"
      26  
      27  
      28  /* If we natively support the load, and if we're unconcerned with extra
      29     barriers (e.g. fully in-order cpu for which barriers are a nop), then
      30     go ahead and expand the operation inline.  */
      31  #if !defined(WANT_SPECIALCASE_RELAXED) && !defined(__OPTIMIZE_SIZE__)
      32  # define EXACT_INLINE(N, DEST, SRC, DONE)			\
      33    if (C2(HAVE_ATOMIC_LDST_,N))					\
      34      {								\
      35        DEST = __atomic_load_n (SRC, __ATOMIC_SEQ_CST);		\
      36        DONE;							\
      37      }
      38  #else
      39  # define EXACT_INLINE(N, DEST, SRC, DONE)
      40  #endif
      41  
      42  
      43  #define EXACT_(N, DEST, SRC, DONE)				\
      44    do {								\
      45      EXACT_INLINE (N, DEST, SRC, DONE);				\
      46      DEST = C3(local_,load_,N) (SRC, smodel);			\
      47      DONE;							\
      48    } while (0)
      49  
      50  #define EXACT(N)						\
      51    do {								\
      52      if (!C2(HAVE_INT,N)) break;					\
      53      if ((uintptr_t)mptr & (N - 1)) break;			\
      54      EXACT_(N, *PTR(N,rptr), PTR(N,mptr), return);		\
      55    } while (0)
      56  
      57  #define LARGER(N)						\
      58    do {								\
      59      if (!C2(HAVE_INT,N)) break;					\
      60      r = (uintptr_t)mptr & (N - 1);				\
      61      a = (uintptr_t)mptr & -N;					\
      62      if (r + n <= N)						\
      63        EXACT_ (N, u.C2(i,N), PTR(N,a), goto Lfinish);		\
      64    } while (0)
      65  
      66  
      67  void
      68  libat_load (size_t n, void *mptr, void *rptr, int smodel)
      69  {
      70    union max_size_u u;
      71    uintptr_t r, a;
      72  
      73    switch (n)
      74      {
      75      case 0:				return;
      76      case 1:		EXACT(1);	goto L4;
      77      case 2:		EXACT(2);	goto L4;
      78      case 4:		EXACT(4);	goto L8;
      79      case 8:		EXACT(8);	goto L16;
      80      case 16:		EXACT(16);	break;
      81  
      82      case 3: L4:		LARGER(4);	/* FALLTHRU */
      83      case 5 ... 7: L8:	LARGER(8);	/* FALLTHRU */
      84      case 9 ... 15: L16:	LARGER(16);	break;
      85  
      86      Lfinish:
      87        memcpy (rptr, u.b + r, n);
      88        return;
      89      }
      90  
      91    pre_seq_barrier (smodel);
      92    libat_lock_n (mptr, n);
      93  
      94    memcpy (rptr, mptr, n);
      95  
      96    libat_unlock_n (mptr, n);
      97    post_seq_barrier (smodel);
      98  }
      99  
     100  EXPORT_ALIAS (load);