Hello, I am trying to use the vmull_p64 instruction. The error I am receiving is: /usr/lib/gcc/aarch64-linux-gnu/6/include/arm_neon.h: In function ‘__v16u mul128(uint64x1_t, uint64x1_t)’: /usr/lib/gcc/aarch64-linux-gnu/6/include/arm_neon.h:21892:1: error: inlining failed in call to always_inline ‘poly128_t vmull_p64(poly64_t, poly64_t)’: target specific option mismatch vmull_p64 (poly64_t a, poly64_t b) ^~~~~~~~~ gf64_vmull.cpp:138:27: note: called from here res = vmull_p64(a64,b64); If instead I call __builtin_aarch64_crypto_pmulldi_ppp(a,b) directly from include/arm_neon.h:21933 I’ll get an ICE: gf64_vmull.cpp:169:1: error: unrecognizable insn: } ^ (insn 35 34 36 2 (set (reg:TI 93 [ _25 ]) (unspec:TI [ (reg/v:DI 105 [ a64 ]) (reg/v:DI 106 [ b64 ]) ] UNSPEC_PMULL)) gf64_vmull.cpp:139 -1 (nil)) gf64_vmull.cpp:169:1: internal compiler error: in extract_insn, at recog.c:2287 I am assuming that this is caused by the fact that the arm device I am using (Odroid-c2) does not support the correct CPU flag (pmull) to execute the instruction vmull_p64 and that is what is meant by gcc’s error: target specific option mismatch, or wether the problem can be solved by using a different flag to pass into gcc. Output of Odroid-c2’s /proc/cpuinfo processor : 3 BogoMIPS : 2.00 Features : fp asimd crc32 CPU implementer : 0x41 CPU architecture: 8 CPU variant : 0x0 CPU part : 0xd03 CPU revision : 4 Thank you, Lincoln