Re: [PATCH 02/24] tcg: Use tcg_gen_negsetcond_*

[Richard Henderson <richard.henderson@linaro.org>]

On 8/8/23 08:55, Peter Maydell wrote:
> On Tue, 8 Aug 2023 at 04:13, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>   tcg/tcg-op-gvec.c | 6 ++----
>>   tcg/tcg-op.c      | 6 ++----
>>   2 files changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/tcg/tcg-op-gvec.c b/tcg/tcg-op-gvec.c
>> index a062239804..e260a07c61 100644
>> --- a/tcg/tcg-op-gvec.c
>> +++ b/tcg/tcg-op-gvec.c
>> @@ -3692,8 +3692,7 @@ static void expand_cmp_i32(uint32_t dofs, uint32_t aofs, uint32_t bofs,
>>       for (i = 0; i < oprsz; i += 4) {
>>           tcg_gen_ld_i32(t0, cpu_env, aofs + i);
>>           tcg_gen_ld_i32(t1, cpu_env, bofs + i);
>> -        tcg_gen_setcond_i32(cond, t0, t0, t1);
>> -        tcg_gen_neg_i32(t0, t0);
>> +        tcg_gen_negsetcond_i32(cond, t0, t0, t1);
>>           tcg_gen_st_i32(t0, cpu_env, dofs + i);
>>       }
> 
> Is it not possible for the optimizer to notice "you did
> a setcond followed by a neg, let me turn it into negsetcond
> for you" ?

Not at present, no.  That sort of peephole optimization is a bit more difficult than what 
we do at present.


r~