On Thu, Jul 03, 2014 at 01:19:19PM -0700, Richard Henderson wrote: > > Grr... Wrong check, obviously - we want to check that tmp + MSB(tmp2) is 0. > > Something like > > setcond_32 tmp2, tmp2, zero, TCG_COND_LT > > add_i32 tmp, tmp2, tmp > > call helper_IOV_if_not_zero tmp > > for 32bit ones and > > setcond_64 tmp2, vc, zero, TCG_COND_LT > > add_i64 tmp, tmp2, tmp > > call helper_IOV_if_not_zero tmp > > for 64bit ones, or would it be better just to pass both arguments to helper > > and let it deal with the check? I'm not familiar enough with TCG, sorry... > > > > I believe I have a tidy solution to these /v insns. New patch set shortly.
Hmm... + tcg_gen_eqv_i64(tmp, va, vb); + tcg_gen_mov_i64(tmp2, va); + tcg_gen_add_i64(vc, va, vb); + tcg_gen_xor_i64(tmp2, tmp2, vc); + tcg_gen_and_i64(tmp, tmp, tmp2); + tcg_gen_shri_i64(tmp, tmp, 63); + tcg_gen_movi_i64(tmp2, 0); + gen_helper_check_overflow(cpu_env, tmp, tmp2); How can that be correct? Suppose a = b = 0. We get tcg_gen_eqv_i64(tmp, va, vb); -> tmp = -1 tcg_gen_mov_i64(tmp2, va); -> tmp2 = 0 tcg_gen_add_i64(vc, va, vb); -> c = 0 tcg_gen_xor_i64(tmp2, tmp2, vc);-> tmp2 = 0 tcg_gen_and_i64(tmp, tmp, tmp2);-> tmp = -1 tcg_gen_shri_i64(tmp, tmp, 63); -> tmp = 1 tcg_gen_movi_i64(tmp2, 0); -> tmp2 = 0 gen_helper_check_overflow(cpu_env, tmp, tmp2); -> not equal, overflow. What am I missing here?
