On 3/19/22 09:06, Wei Li wrote:
> For lock cmpxchg, the situation is more complex. After the instruction
> is completed by tcg_gen_atomic_cmpxchg_tl, it needs a branch to judge
> if oldv == cmpv or not. The instruction only touches accumulator when
> oldv != cmpv.
>
> Signed-off-by: Wei Li <
lw945lw945@yahoo.com>
> ---
> target/i386/tcg/translate.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
> index 05be8d08e6..4fd9c03cb7 100644
> --- a/target/i386/tcg/translate.c
> +++ b/target/i386/tcg/translate.c
> @@ -5360,7 +5360,12 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
> gen_lea_modrm(env, s, modrm);
> tcg_gen_atomic_cmpxchg_tl(oldv, s->A0, cmpv, newv,
> s->mem_index, ot | MO_LE);
> + label1 = gen_new_label();
> + gen_extu(ot, oldv);
> + gen_extu(ot, cmpv);
> + tcg_gen_brcond_tl(TCG_COND_EQ, oldv, cmpv, label1);
> gen_op_mov_reg_v(s, ot, R_EAX, oldv);
This is better addressed with a movcond:
TCGv temp = tcg_temp_new();
tcg_gen_mov_tl(temp, cpu_regs[R_EAX]);
/* Perform the merge into %al or %ax as required by ot. */
gen_op_mov_reg_v(s, ot, R_EAX, oldv);
/* Undo the entire modification to %rax if comparison equal. */
tcg_gen_movcond_tl(TCG_COND_EQ, cpu_regs[R_EAX], oldv, cmpv,
cpu_regs[R_EAX], temp);
tcg_temp_free(temp);
r~