https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89954
--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> --- -------- aarch64 dump------- Failed to match this instruction: (set (reg:SI 95) (xor:SI (zero_extend:SI (mem/c:QI (lo_sum:DI (reg/f:DI 97) (symbol_ref:DI ("*.LANCHOR0") [flags 0x182])) [0 c+0 S1 A8])) (const_int 1 [0x1]))) Successfully matched this instruction: (set (reg:SI 99) (zero_extend:SI (mem/c:QI (lo_sum:DI (reg/f:DI 97) (symbol_ref:DI ("*.LANCHOR0") [flags 0x182])) [0 c+0 S1 A8]))) Successfully matched this instruction: (set (reg:SI 95) (xor:SI (reg:SI 99) (const_int 1 [0x1]))) ---------dump end------------ It looks like there's splitter in aarch64 which combines load+xor+zero_extend to zero_extend(mem) + xor, x86 doesn't have. The simple way is to add corresponding define_split for x86. ---------x86 dump----------- Failed to match this instruction: (set (reg:SI 85) (sign_extend:SI (xor:QI (mem/c:QI (symbol_ref:DI ("c") [flags 0x2] <var_decl 0x7f94fd2e8c60 c>) [0 c+0 S1 A8]) (const_int 1 [0x1])))) -----------dump end----------