On 08/11/2017 11:19 AM, Alistair Francis wrote: > The exclusive store operation should return 0 if the operation updates > memory and 1 if it doesn't. This means that storing tmp in the rd > register is incorrect.
I'm confused as to what you believe is wrong. > tcg_gen_atomic_cmpxchg_i64(tmp, addr, val, tmp, > get_mem_index(s), > - size | MO_ALIGN | s->be_data); > - tcg_gen_setcond_i64(TCG_COND_NE, tmp, tmp, val); Yes, we load the result of the cmpxchg into tmp, but then we immediately overwrite tmp with 0/1 depending on whether the operation succeeded. > > This patch updates the succesful opertion to store 0 into the rd > register instead of tmp. It also adds a branch to fail if the memory > isn't updated. Since we use setcond, a branch is not required. > + tcg_gen_ext_i64(val, val, memop); What is this addition intended to accomplish? Because of the position within the code, you know that memop contains MO_64, so that this is a no-op. r~
