Re: [Qemu-arm] [PATCH 10/67] target/arm: Move test for AL into arm_skip_unless

[Richard Henderson]

On 7/29/19 7:32 AM, Peter Maydell wrote:
> On Fri, 26 Jul 2019 at 18:50, Richard Henderson
> <address@hidden> wrote:
>>
>> We will shortly be calling this function much more often.
>>
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>  target/arm/translate.c | 28 ++++++++++++----------------
>>  1 file changed, 12 insertions(+), 16 deletions(-)
>>
>> diff --git a/target/arm/translate.c b/target/arm/translate.c
>> index 53c46fcdc4..36419025db 100644
>> --- a/target/arm/translate.c
>> +++ b/target/arm/translate.c
>> @@ -7705,8 +7705,14 @@ static void arm_gen_condlabel(DisasContext *s)
>>  /* Skip this instruction if the ARM condition is false */
>>  static void arm_skip_unless(DisasContext *s, uint32_t cond)
>>  {
>> -    arm_gen_condlabel(s);
>> -    arm_gen_test_cc(cond ^ 1, s->condlabel);
>> +    /*
>> +     * Conditionally skip the insn. Note that both 0xe and 0xf mean
>> +     * "always"; 0xf is not "never".
>> +     */
>> +    if (cond < 0xe) {
>> +        arm_gen_condlabel(s);
>> +        arm_gen_test_cc(cond ^ 1, s->condlabel);
>> +    }
>>  }
>>
>>  static void disas_arm_insn(DisasContext *s, unsigned int insn)
>> @@ -7944,11 +7950,9 @@ static void disas_arm_insn(DisasContext *s, unsigned 
>> int insn)
>>          }
>>          goto illegal_op;
>>      }
>> -    if (cond != 0xe) {
>> -        /* if not always execute, we generate a conditional jump to
>> -           next instruction */
>> -        arm_skip_unless(s, cond);
>> -    }
>> +
>> +    arm_skip_unless(s, cond);
>> +
>>      if ((insn & 0x0f900000) == 0x03000000) {
>>          if ((insn & (1 << 21)) == 0) {
>>              ARCH(6T2);
>> @@ -12095,15 +12099,7 @@ static void 
>> thumb_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
>>      dc->insn = insn;
>>
>>      if (dc->condexec_mask && !thumb_insn_is_unconditional(dc, insn)) {
>> -        uint32_t cond = dc->condexec_cond;
>> -
>> -        /*
>> -         * Conditionally skip the insn. Note that both 0xe and 0xf mean
>> -         * "always"; 0xf is not "never".
>> -         */
>> -        if (cond < 0x0e) {
>> -            arm_skip_unless(dc, cond);
>> -        }
>> +        arm_skip_unless(dc, dc->condexec_cond);
>>      }
> 
> In the other callsites for arm_skip_unless() the cond argument
> can never be 0xe or 0xf.
> 
> Reviewed-by: Peter Maydell <address@hidden>

In my original version I included cond in the fields collected by decodetree,
and so every single trans_* function called arm_skip_unless, so that would not
be the case there.

I discarded that in the version posted here, but I still think it might be a
cleaner design overall.

In the short term, maybe I should just discard this patch?


r~