On Wed, Jul 5, 2023 at 2:25 AM simonaytes.yan--- via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > PR target/110438 requests to emit PXOR before VPTERNLOG. This patch > implements that.
I prefer using UNSPEC_INSN_FALSE_DEP like we did for lzcnt/tzcnt/popcnt. i.e. 18866; False dependency happens when destination is only updated by tzcnt, 18867; lzcnt or popcnt. There is no false dependency when destination is 18868; also used in source. 18869(define_insn "*popcountsi2_zext_falsedep" 18870 [(set (match_operand:DI 0 "register_operand" "=r") 18871 (and:DI 18872 (subreg:DI 18873 (popcount:SI 18874 (match_operand:SI 1 "nonimmediate_operand" "rm")) 0) 18875 (const_int 63))) 18876 (unspec [(match_operand:DI 2 "register_operand" "0")] 18877 UNSPEC_INSN_FALSE_DEP) 18878 (clobber (reg:CC FLAGS_REG))] 18879 "TARGET_POPCNT && TARGET_64BIT" BTW, I also posted a patch for this issue at https://gcc.gnu.org/pipermail/gcc-patches/2023-July/623523.html -- BR, Hongtao
