On 25.06.2023 06:42, Hongtao Liu wrote: > On Wed, Jun 21, 2023 at 2:26 PM Jan Beulich via Gcc-patches > <gcc-patches@gcc.gnu.org> wrote: >> >> +(define_code_iterator andor [and ior]) >> +(define_code_attr nlogic [(and "nor") (ior "nand")]) >> +(define_code_attr ternlog_nlogic [(and "0x11") (ior "0x77")]) >> + >> +(define_insn "*<nlogic><mode>3" >> + [(set (match_operand:VI 0 "register_operand" "=v,v") >> + (andor:VI >> + (not:VI (match_operand:VI 1 "bcst_vector_operand" "%v,v")) >> + (not:VI (match_operand:VI 2 "bcst_vector_operand" "vBr,m"))))] > I'm thinking of doing it in simplify_rtx or gimple match.pd to transform > (and (not op1)) (not op2)) -> (not: (ior: op1 op2))
This wouldn't be a win (not + andn) -> (or + not), but what's more important is ... > (ior (not op1) (not op2)) -> (not : (and op1 op2)) > > Even w/o avx512f, the transformation should also benefit since it > takes less logic operations 3 -> 2.(or 2 -> 2 for pandn). ... that these transformations (from the, as per the doc, canonical representation of nand and nor) are already occurring in common code, _if_ no suitable insn can be found. That was at least the conclusion I drew from looking around a lot, supported by the code that's generated prior to this change. Jan
