We've accumulated a few bit-twiddling hacks to get the compiler to
emit a rotate instruction. Since we have a macro for that, let's use
it, as in the attached. I thought the new call sites would look better
with a "left" version, so I added a new macro for that. That's not
necessary, however.
Some comments now look a bit too obvious to keep around, but maybe
they should be replaced with a "why", instead of a "what":
/* rotate hashkey left 1 bit at each step */
- hashkey = (hashkey << 1) | ((hashkey &
0x80000000) ? 1 : 0);
+ hashkey = pg_rotate_left32(hashkey, 1);
--
John Naylor
EDB: http://www.enterprisedb.com
diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index af6e9c42d8..ce8f6cd047 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -460,7 +460,7 @@ TupleHashTableHash_internal(struct tuplehash_hash *tb,
bool isNull;
/* rotate hashkey left 1 bit at each step */
- hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+ hashkey = pg_rotate_left32(hashkey, 1);
attr = slot_getattr(slot, att, &isNull);
diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c
index 4d68a8b97b..6f9d0f9487 100644
--- a/src/backend/executor/nodeHash.c
+++ b/src/backend/executor/nodeHash.c
@@ -1841,7 +1841,7 @@ ExecHashGetHashValue(HashJoinTable hashtable,
bool isNull;
/* rotate hashkey left 1 bit at each step */
- hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+ hashkey = pg_rotate_left32(hashkey, 1);
/*
* Get the join attribute value of the tuple
diff --git a/src/backend/executor/nodeMemoize.c b/src/backend/executor/nodeMemoize.c
index 55cdd5c4d9..e32e4c04e6 100644
--- a/src/backend/executor/nodeMemoize.c
+++ b/src/backend/executor/nodeMemoize.c
@@ -167,7 +167,7 @@ MemoizeHash_hash(struct memoize_hash *tb, const MemoizeKey *key)
for (int i = 0; i < numkeys; i++)
{
/* rotate hashkey left 1 bit at each step */
- hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+ hashkey = pg_rotate_left32(hashkey, 1);
if (!pslot->tts_isnull[i]) /* treat nulls as having hash key 0 */
{
@@ -190,7 +190,7 @@ MemoizeHash_hash(struct memoize_hash *tb, const MemoizeKey *key)
for (int i = 0; i < numkeys; i++)
{
/* rotate hashkey left 1 bit at each step */
- hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+ hashkey = pg_rotate_left32(hashkey, 1);
if (!pslot->tts_isnull[i]) /* treat nulls as having hash key 0 */
{
diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c
index eb83088089..ec073e1ed0 100644
--- a/src/backend/utils/cache/catcache.c
+++ b/src/backend/utils/cache/catcache.c
@@ -26,6 +26,7 @@
#include "catalog/pg_type.h"
#include "common/hashfn.h"
#include "miscadmin.h"
+#include "port/pg_bitutils.h"
#ifdef CATCACHE_STATS
#include "storage/ipc.h" /* for on_proc_exit */
#endif
@@ -281,25 +282,18 @@ CatalogCacheComputeHashValue(CatCache *cache, int nkeys,
{
case 4:
oneHash = (cc_hashfunc[3]) (v4);
-
- hashValue ^= oneHash << 24;
- hashValue ^= oneHash >> 8;
+ hashValue ^= pg_rotate_left32(oneHash, 24);
/* FALLTHROUGH */
case 3:
oneHash = (cc_hashfunc[2]) (v3);
-
- hashValue ^= oneHash << 16;
- hashValue ^= oneHash >> 16;
+ hashValue ^= pg_rotate_left32(oneHash, 16);
/* FALLTHROUGH */
case 2:
oneHash = (cc_hashfunc[1]) (v2);
-
- hashValue ^= oneHash << 8;
- hashValue ^= oneHash >> 24;
+ hashValue ^= pg_rotate_left32(oneHash, 8);
/* FALLTHROUGH */
case 1:
oneHash = (cc_hashfunc[0]) (v1);
-
hashValue ^= oneHash;
break;
default:
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 44c74fb974..65aa5ec29d 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -285,12 +285,18 @@ extern int pg_popcount64(uint64 word);
extern uint64 pg_popcount(const char *buf, int bytes);
/*
- * Rotate the bits of "word" to the right by n bits.
+ * Rotate the bits of word to the right/left by n bits.
*/
static inline uint32
pg_rotate_right32(uint32 word, int n)
{
- return (word >> n) | (word << (sizeof(word) * BITS_PER_BYTE - n));
+ return (word >> n) | (word << (32 - n));
+}
+
+static inline uint32
+pg_rotate_left32(uint32 word, int n)
+{
+ return (word << n) | (word >> (32 - n));
}
#endif /* PG_BITUTILS_H */
