Re: [Qemu-arm] [Qemu-devel] [PATCH 18/20] target/arm: Implement BLXNS

[Peter Maydell]

On 5 October 2017 at 19:56, Richard Henderson
<address@hidden> wrote:
> On 09/22/2017 11:00 AM, Peter Maydell wrote:
>> +void HELPER(v7m_blxns)(CPUARMState *env, uint32_t dest)
>> +{
> ...
>> +    if (dest & 1) {
>> +        /* target is Secure, so this is just a normal BLX,
>> +         * except that the low bit doesn't indicate Thumb/not.
>> +         */
>> +        env->regs[14] = nextinst;
>> +        env->thumb = 1;
>> +        env->regs[15] = dest & ~1;
>> +        return;
>> +    }
> ...
>> +    switch_v7m_security_state(env, dest & 1);
>> +    env->thumb = 1;
>> +    env->regs[15] = dest & ~1;
>
> dest & 1 is known to be 0.

Yes. I liked the symmetry with the tail end of the v7m_bxns helper,
which is conceptually doing the same thing, and assumed the
compiler would be smart enough not to generate unnecessary code.

>> +static inline void gen_blxns(DisasContext *s, int rm)
>> +{
>> +    TCGv_i32 var = load_reg(s, rm);
>> +
>> +    /* We don't need to sync condexec state, for the same reason as blxns.
>
> s/blxns/bxns/ ?

Yes.

thanks
-- PMM