On Tue, Dec 6, 2022 at 12:57 PM Tom Lane <t...@sss.pgh.pa.us> wrote:
> > Well, they've already escaped to tidbitmap.c as a copy. How do you feel
> > about going that route?
>
> Not terribly pleased with that either, I must admit.
Okay, I won't pursue that further.
> If we do put RIGHTMOST_ONE functionality into pg_bitutils.h,
> I'd envision it as pg_bitutils.h exporting both 32-bit and
> 64-bit versions of that, and then bitmapset.c choosing the
> appropriate one just like it chooses bmw_rightmost_one_pos.
Here's a quick go at that. I've not attempted to use it for what I need,
but it looks like it fits the bill.
--
John Naylor
EDB: http://www.enterprisedb.com
src/backend/nodes/bitmapset.c | 36 ++----------------------------------
src/include/nodes/bitmapset.h | 16 ++++++++++++++--
src/include/port/pg_bitutils.h | 31 +++++++++++++++++++++++++++++++
src/tools/pgindent/typedefs.list | 1 -
4 files changed, 47 insertions(+), 37 deletions(-)
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b7b274aeff..4384ff591d 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -32,39 +32,7 @@
#define BITMAPSET_SIZE(nwords) \
(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
-/*----------
- * This is a well-known cute trick for isolating the rightmost one-bit
- * in a word. It assumes two's complement arithmetic. Consider any
- * nonzero value, and focus attention on the rightmost one. The value is
- * then something like
- * xxxxxx10000
- * where x's are unspecified bits. The two's complement negative is formed
- * by inverting all the bits and adding one. Inversion gives
- * yyyyyy01111
- * where each y is the inverse of the corresponding x. Incrementing gives
- * yyyyyy10000
- * and then ANDing with the original value gives
- * 00000010000
- * This works for all cases except original value = zero, where of course
- * we get zero.
- *----------
- */
-#define RIGHTMOST_ONE(x) ((signedbitmapword) (x) & -((signedbitmapword) (x)))
-
-#define HAS_MULTIPLE_ONES(x) ((bitmapword) RIGHTMOST_ONE(x) != (x))
-
-/* Select appropriate bit-twiddling functions for bitmap word size */
-#if BITS_PER_BITMAPWORD == 32
-#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos32(w)
-#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos32(w)
-#define bmw_popcount(w) pg_popcount32(w)
-#elif BITS_PER_BITMAPWORD == 64
-#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos64(w)
-#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos64(w)
-#define bmw_popcount(w) pg_popcount64(w)
-#else
-#error "invalid BITS_PER_BITMAPWORD"
-#endif
+#define HAS_MULTIPLE_ONES(x) (bmw_rightmost_one(x) != (x))
/*
@@ -1013,7 +981,7 @@ bms_first_member(Bitmapset *a)
{
int result;
- w = RIGHTMOST_ONE(w);
+ w = bmw_rightmost_one(w);
a->words[wordnum] &= ~w;
result = wordnum * BITS_PER_BITMAPWORD;
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2792281658..fdc504596b 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -38,13 +38,11 @@ struct List;
#define BITS_PER_BITMAPWORD 64
typedef uint64 bitmapword; /* must be an unsigned type */
-typedef int64 signedbitmapword; /* must be the matching signed type */
#else
#define BITS_PER_BITMAPWORD 32
typedef uint32 bitmapword; /* must be an unsigned type */
-typedef int32 signedbitmapword; /* must be the matching signed type */
#endif
@@ -75,6 +73,20 @@ typedef enum
BMS_MULTIPLE /* >1 member */
} BMS_Membership;
+/* Select appropriate bit-twiddling functions for bitmap word size */
+#if BITS_PER_BITMAPWORD == 32
+#define bmw_rightmost_one(w) pg_rightmost_one32(w)
+#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos32(w)
+#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos32(w)
+#define bmw_popcount(w) pg_popcount32(w)
+#elif BITS_PER_BITMAPWORD == 64
+#define bmw_rightmost_one(w) pg_rightmost_one64(w)
+#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos64(w)
+#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos64(w)
+#define bmw_popcount(w) pg_popcount64(w)
+#else
+#error "invalid BITS_PER_BITMAPWORD"
+#endif
/*
* function prototypes in nodes/bitmapset.c
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 814e0b2dba..f95b6afd86 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -17,6 +17,37 @@ extern PGDLLIMPORT const uint8 pg_leftmost_one_pos[256];
extern PGDLLIMPORT const uint8 pg_rightmost_one_pos[256];
extern PGDLLIMPORT const uint8 pg_number_of_ones[256];
+/*----------
+ * This is a well-known cute trick for isolating the rightmost one-bit
+ * in a word. It assumes two's complement arithmetic. Consider any
+ * nonzero value, and focus attention on the rightmost one. The value is
+ * then something like
+ * xxxxxx10000
+ * where x's are unspecified bits. The two's complement negative is formed
+ * by inverting all the bits and adding one. Inversion gives
+ * yyyyyy01111
+ * where each y is the inverse of the corresponding x. Incrementing gives
+ * yyyyyy10000
+ * and then ANDing with the original value gives
+ * 00000010000
+ * This works for all cases except original value = zero, where of course
+ * we get zero.
+ *----------
+ */
+static inline uint32
+pg_rightmost_one32(uint32 word)
+{
+ int32 result = (int32) word & -((int32) word);
+ return (uint32) result;
+}
+
+static inline uint64
+pg_rightmost_one64(uint64 word)
+{
+ int64 result = (int64) word & -((int64) word);
+ return (uint64) result;
+}
+
/*
* pg_leftmost_one_pos32
* Returns the position of the most significant set bit in "word",
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 58daeca831..68df6ddc0b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -3651,7 +3651,6 @@ shmem_request_hook_type
shmem_startup_hook_type
sig_atomic_t
sigjmp_buf
-signedbitmapword
sigset_t
size_t
slist_head
