On 2019-Feb-14, Tom Lane wrote: > I think we need a clean test for __builtin_popcount(), and to be willing > to use it if available, independently of -mpopcnt. Then separately we > should test to see if -mpopcnt works, probably with the same > infrastructure we use for checking for other compiler flags, viz > > # Optimization flags for specific files that benefit from vectorization > PGAC_PROG_CC_VAR_OPT(CFLAGS_VECTOR, [-funroll-loops]) > PGAC_PROG_CC_VAR_OPT(CFLAGS_VECTOR, [-ftree-vectorize]) > + # Optimization flags for bit-twiddling > + PGAC_PROG_CC_VAR_OPT(CFLAGS_POPCNT, [-mpopcnt]) > # We want to suppress clang's unhelpful unused-command-line-argument > warnings > > Then the correct test to see if we want to build pg_popcount.c (BTW, > please pick a less generic name for that) and the choose function > is whether we have *both* HAVE__BUILTIN_POPCOUNT and nonempty > CFLAGS_POPCNT.
Yeah, this works. I'll post the patch tomorrow. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
