On Mon, Jan 29, 2024 at 01:30:47PM -0300, Ranier Vilela wrote: > 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'm currently +0.1 for this change. I don't see any huge problem with trimming a few instructions, but I'm dubious there's any measurable impact. However, a cycle saved is a cycle earned... -#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) I'm curious why we'd cast to bitmapword and not straight to uint32. I don't think the intent is that callers will provide a bitmapword to these macros. I also wonder if it's worth asserting that x is >= 0 before casting here. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
