bool
SIZE(libat_compare_exchange) (UTYPE *mptr, UTYPE *eptr, UTYPE newval,
int smodel, int fmodel UNUSED)
{
if (maybe_specialcase_relaxed(smodel))
return atomic_compare_exchange_n (mptr, eptr, newval, false,
__ATOMIC_RELAXED, __ATOMIC_RELAXED);
else if (maybe_specialcase_acqrel(smodel))
return atomic_compare_exchange_n (mptr, eptr, newval, false,
__ATOMIC_ACQ_REL, __ATOMIC_RELAXED);
else
return atomic_compare_exchange_n (mptr, eptr, newval, false,
__ATOMIC_SEQ_CST, __ATOMIC_RELAXED);
}
static int atomic_hash_table_update_one_file(english_word *word){
uint64_t hashv=fnv_hash(word->str,word->len);
uint64_t index=hashv%global_hash_table_size;
//this next line results in a lot of cache misses
//for obvious reasons
if(!global_hash_table[index]){//word isn't in the hash table, add it
uint8_t *mem=xmalloc(word->len);
word->str=(char*)my_strcpy(mem,(uint8_t*)word->str,word->len);
void *prev=global_hash_table[index];
int test=atomic_compare_exchange_n(global_hash_table+index,&prev,word);
if(test){
//we added the word
//this needs to be atomic to prevent two threads writing different
//values to the same index of indices
uint64_t old_indices_index=atomic_fetch_add(&indices_index,1);
//this doesn't need to be atomic, since indices_index will never be
//decremented, so no one else will change this
hash_table_indices[old_indices_index]=index;
goto end1;
}
//else, someone else changed the value of global_hash_table[index] before us
}
while(1){
do {
//see if the value in the table is the same as our value
//if so update the value already in the table
if(string_compare(global_hash_table[index],word)){
//atomically increment word count
atomic_add(&global_hash_table[index]->count,1);
goto end0;
}
} while(global_hash_table[++index]);
//not in the table use next free index (if we can)
void *prev=global_hash_table[index];
int test=atomic_compare_exchange_n(global_hash_table+index,&prev,word);
if(test){
uint64_t old_indices_index=atomic_fetch_add(&indices_index,1);
hash_table_indices[old_indices_index]=index;
goto end1;
}
//if !test the compare exchange failed and we need to keep looping
}
end0:
return 0;
end1:
return 1;
}
UTYPE
SIZE(libat_load) (UTYPE *mptr, int smodel)
{
UTYPE t = 0;
if (maybe_specialcase_relaxed(smodel))
atomic_compare_exchange_n (mptr, &t, 0, true,
__ATOMIC_RELAXED, __ATOMIC_RELAXED);
else if (maybe_specialcase_acqrel(smodel))
atomic_compare_exchange_n (mptr, &t, 0, true,
__ATOMIC_ACQ_REL, __ATOMIC_ACQ_REL);
else
atomic_compare_exchange_n (mptr, &t, 0, true,
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
return t;
}
void
SIZE(libat_store) (UTYPE *mptr, UTYPE newval, int smodel)
{
UTYPE oldval;
pre_barrier (smodel);
oldval = *mptr;
while (!atomic_compare_exchange_n (mptr, &oldval, newval, true,
__ATOMIC_RELAXED, __ATOMIC_RELAXED))
continue;
post_barrier (smodel);
}
UTYPE
SIZE(C3(libat_,NAME,_fetch)) (UTYPE *mptr, UTYPE opval, int smodel)
{
UTYPE oldval, t;
pre_barrier (smodel);
oldval = *mptr;
do
{
t = OP(oldval, opval);
}
while (!atomic_compare_exchange_n (mptr, &oldval, t, true,
__ATOMIC_RELAXED, __ATOMIC_RELAXED));
post_barrier (smodel);
return t;
}
