[MiNT] [GCC] volatile and -O2

[Arnaud BERCEGEAY <arnaud.bercegeay@free.fr>]

Hi list,

I have a pb in gemlib with GCC when the optimisation flag is set (-O2).

Here is a sample. just type
$ gcc -o test.tos test.c

to build it. You don't have to link gemlib.

<code>

#include <stdio.h>

typedef struct
{
       short       *control;
       short       *global;
       const short *intin;
       short       *intout;
       const long  *addrin;
       long        *addrout;
} AESPB;

static inline void
_aes_trap (AESPB * aespb)
{
       __asm__ volatile ("
               move.l %0, d1;    | &aespb
               move.w  #200,d0;
               trap    #2;
               "
               :
               : "a"(aespb)
               : "d0","d1"
       );
}

static short
mt_appl_init(short *global_aes)
{
       static short    aes_control[5]={10,0,1,0,0};
       short                   aes_intin[16];
#if USE_VOLATILE
       volatile
#endif
       short                   aes_intout[16];
       long                    aes_addrin[16];
#if USE_VOLATILE
       volatile
#endif
       long                    aes_addrout[16];
       AESPB aes_params;
       aes_params.control = &aes_control[0];
       aes_params.global  = &global_aes[0];
       aes_params.intin   = &aes_intin[0];
#if USE_VOLATILE
       (volatile short*)
#endif
       aes_params.intout  = aes_intout;
       aes_params.addrin  = &aes_addrin[0];
#if USE_VOLATILE
       (volatile long *)
#endif
       aes_params.addrout = aes_addrout;
       /* clear some variable that may be used to check if an AES is 
loaded */
       global_aes[0] = 0;  /* AES version number */
       global_aes[2] = -1;  /* AES application ID */
       aes_intout[0] = -1;  /* AES application ID */

       _aes_trap(&aes_params);

       return aes_intout[0];
}

int main( void) {
       int i, appid;
       short aes_global[16]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
       appid = mt_appl_init(aes_global);
       printf("\nUSE_VOLATILE "
#if USE_VOLATILE
                       "is defined = 1"
#else
                       "is not defined"
#endif
                       "\n");
       printf("mt_appl_init() return %d\n",appid);
       for (i=0; i<16; i++)
               printf("aes_global[%2d] = %d\n",i,aes_global[i]);
       return 0;
}

<code>

The problem is in the following lines:

       aes_intout[0] = -1;  /* AES application ID */
       _aes_trap(&aes_params);
       return aes_intout[0];

If optimisation is set (-O2), this function always returns -1.
If i remove the optimisation flag, or add the "volatile" keyword before 
intout (compile the example above with -DUSE_VOLATILE=1), all works fine.

How can i tell GCC that the function _aes_trap() may touch aes_intout ?
Is it a GCC 2.95.3 bug, or a pb in the C code above.

best regards,
Arnaud.