Re: [Qemu-devel] [PATCH 01/13] target-arm: A64: add support for conditional select

[Peter Maydell]

On 6 December 2013 16:44, Richard Henderson <address@hidden> wrote:
> On 12/07/2013 01:45 AM, Peter Maydell wrote:
>> On 5 December 2013 22:26, Richard Henderson <address@hidden> wrote:
>>> On 12/06/2013 10:51 AM, Peter Maydell wrote:
>>>> +    if (cond >= 0x0e) { /* condition "always" */
>>>> +        tcg_src = read_cpu_reg(s, rn, sf);
>>>> +        tcg_gen_mov_i64(tcg_rd, tcg_src);
>>>
>>> I wonder if it's worth adding that 0x0[ef] case to the generic condition
>>> processing rather than keep replicating it everywhere.
>>
>> I think "always true" is a special case anyway because you don't
>> want to emit any kind of branching/label logic at all.
>
> Sure, but unlike unconditional branches, which are useful to special-case, one
> sort of expects never to see an unconditional conditional move.  Given
> TCG_COND_ALWAYS, we can re-use generic logic and have things fall out
> relatively easily.

I guess. It doesn't seem much worth adding extra code to arm_gen_test_cc
that we expect to become redundant if/when we do these insns "properly"
with setcond/movcond, though, so I think it's OK like this for now.

thanks
-- PMM