This function is not just slower than xxhash, it is slower than
even libiberty's iterative_hash, so there does not seem to be
a reason for it to exist.
------------------------------------------------------------
Benchmark Time CPU Iterations
------------------------------------------------------------
BM_xxh3 11 ns 11 ns
66127192
BM_xxh32 19 ns 19 ns
36792609
BM_xxh64 16 ns 16 ns
42941328
BM_city32 26 ns 26 ns
27028370
BM_city64 17 ns 17 ns
40472793
BM_iterative_hash 77 ns 77 ns
9088854
BM_bcache_hash 125 ns 125 ns
5599232
gdb/ChangeLog:
2019-12-03 Christian Biesinger <cbiesinger@google.com>
* bcache.c (hash): Remove.
(hash_continue): Remove.
* bcache.h (hash): Remove.
(hash_continue): Remove.
(struct bcache) <ctor>: Update.
* psymtab.c (psymbol_hash): Update.
* stabsread.c (hashname): Update.
* utils.h (fast_hash): Add an argument for a start value,
defaulting to zero.
Change-Id: I107f013eda5fdd3293326b5a206be43155dae0f8
+2019-12-03 Christian Biesinger <cbiesinger@google.com>
+
+ * bcache.c (hash): Remove.
+ (hash_continue): Remove.
+ * bcache.h (hash): Remove.
+ (hash_continue): Remove.
+ (struct bcache) <ctor>: Update.
+ * psymtab.c (psymbol_hash): Update.
+ * stabsread.c (hashname): Update.
+ * utils.h (fast_hash): Add an argument for a start value,
+ defaulting to zero.
+
2019-12-03 Philippe Waroquiers <philippe.waroquiers@skynet.be>
* symtab.c (symbol_cache_clear_slot): Move close to cleared type.
(destroy_block_symbol_cache): New function.
d;
};
-/* The old hash function was stolen from SDBM. This is what DB 3.0
- uses now, and is better than the old one. */
-\f
-unsigned long
-hash(const void *addr, int length)
-{
- return hash_continue (addr, length, 0);
-}
-
-/* Continue the calculation of the hash H at the given address. */
-
-unsigned long
-hash_continue (const void *addr, int length, unsigned long h)
-{
- const unsigned char *k, *e;
-
- k = (const unsigned char *)addr;
- e = k+length;
- for (; k< e;++k)
- {
- h *=16777619;
- h ^= *k;
- }
- return (h);
-}
\f
/* Growing the bcache's hash table. */
struct bstring;
-/* The hash functions */
-extern unsigned long hash (const void *addr, int length);
-extern unsigned long hash_continue (const void *addr, int length,
- unsigned long h);
-
struct bcache
{
/* Allocate a bcache. HASH_FN and COMPARE_FN can be used to pass in
custom hash, and compare functions to be used by this bcache. If
- HASH_FUNCTION is NULL hash() is used and if COMPARE_FUNCTION is
+ HASH_FUNCTION is NULL fast_hash() is used and if COMPARE_FUNCTION is
NULL memcmp() is used. */
explicit bcache (unsigned long (*hash_fn)(const void *,
int length) = nullptr,
int (*compare_fn)(const void *, const void *,
int length) = nullptr)
- : m_hash_function (hash_fn == nullptr ? hash : hash_fn),
+ : m_hash_function (hash_fn == nullptr ? default_hash : hash_fn),
m_compare_function (compare_fn == nullptr ? compare : compare_fn)
{
}
/* Default compare function. */
static int compare (const void *addr1, const void *addr2, int length);
+ /* Default hash function. */
+ static unsigned long default_hash (const void *ptr, int length)
+ {
+ return fast_hash (ptr, length, 0);
+ }
+
/* Expand the hash table. */
void expand_hash_table ();
};
unsigned int domain = psymbol->domain;
unsigned int theclass = psymbol->aclass;
- h = hash_continue (&psymbol->ginfo.value, sizeof (psymbol->ginfo.value), h);
- h = hash_continue (&lang, sizeof (unsigned int), h);
- h = hash_continue (&domain, sizeof (unsigned int), h);
- h = hash_continue (&theclass, sizeof (unsigned int), h);
+ h = fast_hash (&psymbol->ginfo.value, sizeof (psymbol->ginfo.value), h);
+ h = fast_hash (&lang, sizeof (unsigned int), h);
+ h = fast_hash (&domain, sizeof (unsigned int), h);
+ h = fast_hash (&theclass, sizeof (unsigned int), h);
/* Note that psymbol names are interned via symbol_set_names, so
there's no need to hash the contents of the name here. */
- h = hash_continue (&psymbol->ginfo.name,
- sizeof (psymbol->ginfo.name), h);
+ h = fast_hash (&psymbol->ginfo.name, sizeof (psymbol->ginfo.name), h);
return h;
}
int
hashname (const char *name)
{
- return hash (name, strlen (name)) % HASHSIZE;
+ return fast_hash (name, strlen (name)) % HASHSIZE;
}
/* Initializer for this module. */
const gdb_byte *source, ULONGEST source_offset,
ULONGEST nbits, int bits_big_endian);
-/* A fast hashing function. This can be used to hash strings in a fast way
+/* A fast hashing function. This can be used to hash data in a fast way
when the length is known. If no fast hashing library is available, falls
- back to iterative_hash from libiberty. */
+ back to iterative_hash from libiberty. START_VALUE can be set to
+ continue hashing from a previous value. */
static inline unsigned int
-fast_hash (const char* str, size_t len)
+fast_hash (const void *ptr, size_t len, unsigned int start_value = 0)
{
#ifdef HAVE_LIBXXHASH
- return XXH64 (str, len, 0);
+ return XXH64 (ptr, len, start_value);
#else
- return iterative_hash (str, len, 0);
+ return iterative_hash (ptr, len, start_value);
#endif
}
projects / binutils-gdb.git / commitdiff