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Make the hashing in VG_(record_ExeContext) 64-bit clean and more

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robust.  Also incrementally rearrange the hash chains during searches.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@6341
This commit is contained in:
Julian Seward 2006-10-24 21:43:38 +00:00
parent 0a12dbcaf4
commit b2c70d2846
1 changed files with 32 additions and 4 deletions
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36
coregrind/m_execontext.c
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@ -185,6 +185,13 @@ Bool VG_(eq_ExeContext) ( VgRes res, ExeContext* e1, ExeContext* e2 )
on the returned ExeContext* values themselves. Inspired by Hugs's
Text type.
*/
static inline UWord ROLW ( UWord w, Int n )
{
Int bpw = 8 * sizeof(UWord);
w = (w << n) | (w >> (bpw-n));
return w;
}
ExeContext* VG_(record_ExeContext) ( ThreadId tid )
{
Int i;
@ -194,6 +201,12 @@ ExeContext* VG_(record_ExeContext) ( ThreadId tid )
ExeContext* new_ec;
ExeContext* list;
UInt n_ips;
ExeContext *prev2, *prev;
static UInt ctr = 0;
vg_assert(sizeof(void*) == sizeof(UWord));
vg_assert(sizeof(void*) == sizeof(Addr));
init_ExeContext_storage();
vg_assert(VG_(clo_backtrace_size) >= 1 &&
@ -208,15 +221,19 @@ ExeContext* VG_(record_ExeContext) ( ThreadId tid )
hash = 0;
for (i = 0; i < n_ips; i++) {
hash ^= ips[i];
hash = (hash << 29) | (hash >> 3);
hash = ROLW(hash, 19);
}
if (0) VG_(printf)("hash 0x%lx ", hash);
hash = hash % N_EC_LISTS;
if (0) VG_(printf)("%lu\n", hash);
/* And (the expensive bit) look a matching entry in the list. */
ec_searchreqs++;
list = ec_list[hash];
prev2 = NULL;
prev = NULL;
list = ec_list[hash];
while (True) {
if (list == NULL) break;
@ -229,11 +246,22 @@ ExeContext* VG_(record_ExeContext) ( ThreadId tid )
}
}
if (same) break;
list = list->next;
prev2 = prev;
prev = list;
list = list->next;
}
if (list != NULL) {
/* Yay! We found it. */
/* Yay! We found it. Once every 8 searches, move it one step
closer to the start of the list to make future searches
cheaper. */
if (prev2 && prev && 0 == ((ctr++) & 7)) {
vg_assert(prev2->next == prev);
vg_assert(prev->next == list);
prev2->next = list;
prev->next = list->next;
list->next = prev;
}
return list;
}