On Sat, Mar 21, 2026, at 2:36 PM, Andres Freund wrote: > Hi, > > On 2026-03-21 12:54:10 -0400, Greg Burd wrote: >> Attached is a small patch that enables hardware popcount on RISC-V when >> available and also sets the arch flag to 'rv64gc_zbb' flag when appropriate. > > Maybe I'm missing something: How is the latter approach safe without a runtime > check? Just because it compiled on the build machine with -march=rv64gc_zbb > added doesn't mean it runs on either the build machine or any other machine? > > If this worked, the compiler could just always specify -march=rv64gc_zbb, no?
Hey Andres, thanks for taking a look. You are correct, mea culpa for not catching this before I sent it out. If the second test succeeds the patch will add `-march=rv64gc_zbb` to `CFLAGS` globally, which means without the runtime check the binary will crash with SIGILL on systems without Zbb. I'll rework... :) > Greetings, > > Andres Freund best. -greg
