Use bitwise rotate functions in more places

There were a number of places in the code that used bespoke bit-twiddling
expressions to do bitwise rotation. While we've had pg_rotate_right32()
for a while now, we hadn't gotten around to standardizing on that. Do so
now. Since many potential call sites look more natural with the "left"
equivalent, add that function too.

Reviewed by Tom Lane and Yugo Nagata

Discussion:
https://www.postgresql.org/message-id/CAFBsxsH7c1LC0CGZ0ADCBXLHU5-%3DKNXx-r7tHYPAW51b2HK4Qw%40mail.gmail.com

src/backend/executor/execGrouping.c

@@ -459,8 +459,8 @@ TupleHashTableHash_internal(struct tuplehash_hash *tb,
 		Datum		attr;
 		bool		isNull;
 
-		/* rotate hashkey left 1 bit at each step */
-		hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+		/* combine successive hashkeys by rotating */
+		hashkey = pg_rotate_left32(hashkey, 1);
 
 		attr = slot_getattr(slot, att, &isNull);
 

src/backend/executor/nodeHash.c

@@ -1840,8 +1840,8 @@ ExecHashGetHashValue(HashJoinTable hashtable,
 		Datum		keyval;
 		bool		isNull;
 
-		/* rotate hashkey left 1 bit at each step */
-		hashkey = (hashkey << 1) | ((hashkey & 0x80000000) ? 1 : 0);
+		/* combine successive hashkeys by rotating */
+		hashkey = pg_rotate_left32(hashkey, 1);
 
 		/*
 		 * Get the join attribute value of the tuple

src/backend/executor/nodeMemoize.c

@@ -166,8 +166,8 @@ 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);
+			/* combine successive hashkeys by rotating */
+			hashkey = pg_rotate_left32(hashkey, 1);
 
 			if (!pslot->tts_isnull[i])	/* treat nulls as having hash key 0 */
 			{
@@ -189,8 +189,8 @@ 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);
+			/* combine successive hashkeys by rotating */
+			hashkey = pg_rotate_left32(hashkey, 1);
 
 			if (!pslot->tts_isnull[i])	/* treat nulls as having hash key 0 */
 			{

src/backend/utils/adt/jsonb_util.c

@@ -18,6 +18,7 @@
 #include "common/hashfn.h"
 #include "common/jsonapi.h"
 #include "miscadmin.h"
+#include "port/pg_bitutils.h"
 #include "utils/builtins.h"
 #include "utils/datetime.h"
 #include "utils/json.h"
@@ -1342,7 +1343,7 @@ JsonbHashScalarValue(const JsonbValue *scalarVal, uint32 *hash)
 	 * the previous value left 1 bit, then XOR'ing in the new
 	 * key/value/element's hash value.
 	 */
-	*hash = (*hash << 1) | (*hash >> 31);
+	*hash = pg_rotate_left32(*hash, 1);
 	*hash ^= tmp;
 }
 

src/backend/utils/adt/multirangetypes.c

@@ -38,6 +38,7 @@
 #include "lib/stringinfo.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
+#include "port/pg_bitutils.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/rangetypes.h"
@@ -2772,7 +2773,7 @@ hash_multirange(PG_FUNCTION_ARGS)
 		/* Merge hashes of flags and bounds */
 		range_hash = hash_uint32((uint32) flags);
 		range_hash ^= lower_hash;
-		range_hash = (range_hash << 1) | (range_hash >> 31);
+		range_hash = pg_rotate_left32(range_hash, 1);
 		range_hash ^= upper_hash;
 
 		/*

src/backend/utils/adt/rangetypes.c

@@ -35,6 +35,7 @@
 #include "lib/stringinfo.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
+#include "port/pg_bitutils.h"
 #include "utils/builtins.h"
 #include "utils/date.h"
 #include "utils/lsyscache.h"
@@ -1363,7 +1364,7 @@ hash_range(PG_FUNCTION_ARGS)
 	/* Merge hashes of flags and bounds */
 	result = hash_uint32((uint32) flags);
 	result ^= lower_hash;
-	result = (result << 1) | (result >> 31);
+	result = pg_rotate_left32(result, 1);
 	result ^= upper_hash;
 
 	PG_RETURN_INT32(result);

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:

src/common/hashfn.c

@@ -24,6 +24,7 @@
 #include "postgres.h"
 
 #include "common/hashfn.h"
+#include "port/pg_bitutils.h"
 
 
 /*
@@ -44,8 +45,7 @@
 /* Get a bit mask of the bits set in non-uint32 aligned addresses */
 #define UINT32_ALIGN_MASK (sizeof(uint32) - 1)
 
-/* Rotate a uint32 value left by k bits - note multiple evaluation! */
-#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+#define rot(x,k) pg_rotate_left32(x, k)
 
 /*----------
  * mix -- mix 3 32-bit values reversibly.

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 */