1  /* { dg-do link } */
       2  /* { dg-require-effective-target sync_long_long_runtime } */
       3  /* { dg-options "" } */
       4  /* { dg-options "-march=pentium" { target { { i?86-*-* x86_64-*-* } && ia32 } } } */
       5  /* { dg-final { simulate-thread } } */
       6  
       7  
       8  #include <stdio.h>
       9  #include "simulate-thread.h"
      10  
      11  
      12  /* Testing load for atomicity is a little trickier.  
      13  
      14     Set up the atomic value so that it changes value after every instruction 
      15     is executed.
      16  
      17     Simply alternating between 2 values wouldn't be sufficient since a load of
      18     one part, followed by the load of the second part 2 instructions later would
      19     appear to be valid.
      20  
      21     set up a table of 16 values which change a bit in every byte of the value 
      22     each time, this will give us a 16 instruction cycle before repetition
      23     kicks in, which should be sufficient to detect any issues.  Just to be sure,
      24     we also change the table cycle size during execution. 
      25     
      26     The end result is that all loads should always get one of the values from
      27     the table. Any other pattern means the load failed.  */
      28  
      29  unsigned long long ret;
      30  unsigned long long value = 0;
      31  unsigned long long result = 0;
      32  unsigned long long table[16] = {
      33  0x0000000000000000, 
      34  0x1111111111111111, 
      35  0x2222222222222222, 
      36  0x3333333333333333,
      37  0x4444444444444444,
      38  0x5555555555555555,
      39  0x6666666666666666,
      40  0x7777777777777777,
      41  0x8888888888888888,
      42  0x9999999999999999,
      43  0xAAAAAAAAAAAAAAAA,
      44  0xBBBBBBBBBBBBBBBB,
      45  0xCCCCCCCCCCCCCCCC,
      46  0xDDDDDDDDDDDDDDDD,
      47  0xEEEEEEEEEEEEEEEE,
      48  0xFFFFFFFFFFFFFFFF
      49  };
      50  
      51  int table_cycle_size = 16;
      52  
      53  /* Return 0 if 'result' is a valid value to have loaded.  */
      54  int verify_result ()
      55  {
      56    int x;
      57    int found = 0;
      58  
      59    /* Check entire table for valid values.  */
      60    for (x = 0; x < 16 ; x++)
      61      if (result == table[x])
      62        {
      63  	found = 1;
      64  	break;
      65        }
      66  
      67    if (!found)
      68      printf("FAIL: Invalid result returned from fetch\n");
      69  
      70    return !found;
      71  }
      72  
      73  /* Iterate VALUE through the different valid values. */
      74  void simulate_thread_other_threads ()
      75  {
      76    static int current = 0;
      77  
      78    if (++current >= table_cycle_size)
      79      current = 0;
      80    value = table[current];
      81  }
      82  
      83  int simulate_thread_step_verify ()
      84  {
      85    return verify_result ();
      86  }
      87  
      88  int simulate_thread_final_verify ()
      89  {
      90    return verify_result ();
      91  }
      92  
      93  __attribute__((noinline))
      94  void simulate_thread_main()
      95  {
      96    int x;
      97  
      98    /* Execute loads with value changing at various cyclic values.  */
      99    for (table_cycle_size = 16; table_cycle_size > 4 ; table_cycle_size--)
     100      {
     101        ret = __atomic_load_n (&value, __ATOMIC_SEQ_CST);
     102        /* In order to verify the returned value (which is not atomic), it needs
     103  	 to be atomically stored into another variable and check that.  */
     104        __atomic_store_n (&result, ret, __ATOMIC_SEQ_CST);
     105  
     106        /* Execute the fetch/store a couple of times just to ensure the cycles
     107           have a chance to be interesting.  */
     108        ret = __atomic_load_n (&value, __ATOMIC_SEQ_CST);
     109        __atomic_store_n (&result, ret, __ATOMIC_SEQ_CST);
     110      }
     111  }
     112  
     113  int
     114  main()
     115  {
     116    simulate_thread_main ();
     117    simulate_thread_done ();
     118    return 0;
     119  }