On Fri, Dec 27, 2019 at 9:16 PM David Fetter <da...@fetter.org> wrote: > On Fri, Dec 27, 2019 at 07:02:02PM -0500, John Naylor wrote: > > The lookup table case is less clear. Removing the shift results in > > assembly that looks more like the C code and is slower for me. The > > standard lookup table code uses some magic constants and does its own > > constant folding by shifting 11 (8 + 3). In the absence of testing on > > platforms that will actually exercise this path, it seems the > > open-coded path should keep the shift for now. Thoughts? > > It's probably worth doing the things you've found unambiguous gains > for as a patch, putting it on the next commitfest, and seeing what the > commitfest.cputube.org machinery has to say about it.
Done in the attached. > Maybe it'd be worth trying out a patch that enables CLZ for Windows, > but that seems like a separate issue. Agreed. -- John Naylor https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
v2-0001-Use-the-CLZ-instruction-in-AllocSetFreeIndex.patch
Description: Binary data
