libjava/sysdep/mips/locks.h

   1 // locks.h - Thread synchronization primitives. MIPS implementation.
   2
   3 /* Copyright (C) 2003  Free Software Foundation
   4
   5    This file is part of libgcj.
   6
   7 This software is copyrighted work licensed under the terms of the
   8 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
   9 details.  */
  10
  11 #ifndef __SYSDEP_LOCKS_H__
  12 #define __SYSDEP_LOCKS_H__
  13
  14 /* Integer type big enough for object address.  */
  15 typedef unsigned obj_addr_t __attribute__((__mode__(__pointer__)));
  16
  17
  18 // Atomically replace *addr by new_val if it was initially equal to old.
  19 // Return true if the comparison succeeded.
  20 // Assumed to have acquire semantics, i.e. later memory operations
  21 // cannot execute before the compare_and_swap finishes.
  22 inline static bool
  23 compare_and_swap(volatile obj_addr_t *addr,
  24                  obj_addr_t old,
  25                  obj_addr_t new_val)
  26 {
  27   long result;
  28   __asm__ __volatile__(".set\tpush\n\t"
  29                        ".set\tnoreorder\n\t"
  30                        ".set\tnomacro\n\t"
  31                        "1:\n\t"
  32 #if _MIPS_SIM == _ABIO32
  33                        ".set\tmips2\n\t"
  34 #endif
  35                        "ll\t%[result],0(%[addr])\n\t"
  36                        "bne\t%[result],%[old],2f\n\t"
  37                        "move\t%[result],$0\n\t"        // delay slot
  38                        "move\t%[result],%[new_val]\n\t"
  39                        "sc\t%[result],0(%[addr])\n\t"
  40                        "beq\t%[result],$0,1b\n\t"
  41                        "nop\n\t"                       // delay slot
  42                        "2:\n\t"
  43                        ".set\tpop"
  44           : [result] "=&r" (result)
  45           : [addr] "r" (addr), [new_val] "r" (new_val), [old] "r"(old)
  46           : "memory");
  47   return (bool) result;
  48 }
  49
  50 // Set *addr to new_val with release semantics, i.e. making sure
  51 // that prior loads and stores complete before this
  52 // assignment.
  53 inline static void
  54 release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
  55 {
  56   __asm__ __volatile__(".set\tpush\n\t"
  57 #if _MIPS_SIM == _ABIO32
  58                        ".set\tmips2\n\t"
  59 #endif
  60                        "sync\n\t"
  61                        ".set\tpop" : : : "memory");
  62   *(addr) = new_val;
  63 }
  64
  65 // Compare_and_swap with release semantics instead of acquire semantics.
  66 // On many architecture, the operation makes both guarantees, so the
  67 // implementation can be the same.
  68 inline static bool
  69 compare_and_swap_release(volatile obj_addr_t *addr,
  70                                                      obj_addr_t old,
  71                                                      obj_addr_t new_val)
  72 {
  73   __asm__ __volatile__(".set\tpush\n\t"
  74 #if _MIPS_SIM == _ABIO32
  75                        ".set\tmips2\n\t"
  76 #endif
  77                        "sync\n\t"
  78                        ".set\tpop" : : : "memory");
  79   return compare_and_swap(addr, old, new_val);
  80 }
  81
  82 // Ensure that subsequent instructions do not execute on stale
  83 // data that was loaded from memory before the barrier.
  84 // On X86, the hardware ensures that reads are properly ordered.
  85 inline static void
  86 read_barrier()
  87 {
  88   __asm__ __volatile__(".set\tpush\n\t"
  89 #if _MIPS_SIM == _ABIO32
  90                        ".set\tmips2\n\t"
  91 #endif
  92                        "sync\n\t"
  93                        ".set\tpop" : : : "memory");
  94 }
  95
  96 // Ensure that prior stores to memory are completed with respect to other
  97 // processors.
  98 inline static void
  99 write_barrier()
 100 {
 101   __asm__ __volatile__(".set\tpush\n\t"
 102 #if _MIPS_SIM == _ABIO32
 103                        ".set\tmips2\n\t"
 104 #endif
 105                        "sync\n\t"
 106                        ".set\tpop" : : : "memory");
 107 }
 108
 109 #endif   // __SYSDEP_LOCKS_H__