Hi, IMO I believe that bitmapset can obtain an optimization in the calculation of the WORDNUM and BITNUM macros.
As you know, in bitmapset, negative members are not allowed. if (x < 0) elog(ERROR, "negative bitmapset member not allowed"); Then, allow the compiler to optimize and do the calculations in unsigned. I did a demonstration in compiler explorer. https://godbolt.org/z/c68o43Eq1 It is demonstrated here as well. Generated instructions: GCC 13.2 #define WORDNUM_f1(x) ((x) / BITS_PER_BITMAPWORD) mov eax, DWORD PTR [rbp-20] lea edx, [rax+63] test eax, eax cmovs eax, edx sar eax, 6 mov DWORD PTR [rbp-4], eax #define WORDNUM_f2(x) ((bitmapword) (x) / BITS_PER_BITMAPWORD) mov eax, DWORD PTR [rbp-20] cdqe shr rax, 6 mov DWORD PTR [rbp-4], eax #define BITNUM_f1(x) ((x) % BITS_PER_BITMAPWORD) mov edx, DWORD PTR [rbp-20] mov eax, edx sar eax, 31 shr eax, 26 add edx, eax and edx, 63 sub edx, eax mov DWORD PTR [rbp-4], edx #define BITNUM_f2(x) ((bitmapword) (x) % BITS_PER_BITMAPWORD) mov eax, DWORD PTR [rbp-20] and eax, 63 mov DWORD PTR [rbp-4], eax As you can see, when calculations are done in unsigned, the generated instructions are optimized. Patch attached. Best regards, Ranier Vilela
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c index 65805d4527..0765dd42c2 100644 --- a/src/backend/nodes/bitmapset.c +++ b/src/backend/nodes/bitmapset.c @@ -44,8 +44,8 @@ #include "port/pg_bitutils.h" -#define WORDNUM(x) ((x) / BITS_PER_BITMAPWORD) -#define BITNUM(x) ((x) % BITS_PER_BITMAPWORD) +#define WORDNUM(x) ((bitmapword)(x) / BITS_PER_BITMAPWORD) +#define BITNUM(x) ((bitmapword)(x) % BITS_PER_BITMAPWORD) #define BITMAPSET_SIZE(nwords) \ (offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
