Re: [Qemu-devel] [PATCH v3 36/38] target-microblaze: Use tcg_gen_movcond in eval_cond_jmp

[Edgar E. Iglesias]

On Thu, May 17, 2018 at 11:48:35AM -0300, Philippe Mathieu-Daudé wrote:
> Hi Edgar,
> 
> On 05/17/2018 11:22 AM, Philippe Mathieu-Daudé wrote:
> > On 05/16/2018 03:51 PM, Edgar E. Iglesias wrote:
> >> From: "Edgar E. Iglesias" <address@hidden>
> >>
> >> Cleanup eval_cond_jmp to use tcg_gen_movcond_i64().
> >> No functional change.
> >>
> >> Suggested-by: Richard Henderson <address@hidden>
> >> Signed-off-by: Edgar E. Iglesias <address@hidden>
> >> ---
> >>  target/microblaze/translate.c | 16 ++++++++++------
> >>  1 file changed, 10 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/target/microblaze/translate.c b/target/microblaze/translate.c
> >> index a846797d9c..78c2855ff0 100644
> >> --- a/target/microblaze/translate.c
> >> +++ b/target/microblaze/translate.c
> >> @@ -1171,12 +1171,16 @@ static inline void eval_cc(DisasContext *dc, 
> >> unsigned int cc,
> >>  
> >>  static void eval_cond_jmp(DisasContext *dc, TCGv_i64 pc_true, TCGv_i64 
> >> pc_false)
> >>  {
> >> -    TCGLabel *l1 = gen_new_label();
> >> -    /* Conditional jmp.  */
> >> -    tcg_gen_mov_i64(cpu_SR[SR_PC], pc_false);
> >> -    tcg_gen_brcondi_i32(TCG_COND_EQ, env_btaken, 0, l1);
> >> -    tcg_gen_mov_i64(cpu_SR[SR_PC], pc_true);
> >> -    gen_set_label(l1);
> >> +    TCGv_i64 tmp_btaken = tcg_temp_new_i64();
> >> +    TCGv_i64 tmp_zero = tcg_const_i64(0);
> 
> Why not use cpu_R[0] directly?
> 
> I wonder, maybe the current model doesn't not have R0 hardwired to 0?

It does but cpu_R[0] is 32bit so we would still need a temp to extend it...

Cheers,
Edgar

> 
> >> +
> >> +    tcg_gen_extu_i32_i64(tmp_btaken, env_btaken);
> > 
> > env_btaken is i32, ok.
> > 
> > Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
> > 
> >> +    tcg_gen_movcond_i64(TCG_COND_NE, cpu_SR[SR_PC],
> >> +                        tmp_btaken, tmp_zero,
> >> +                        pc_true, pc_false);
> 
> So we could drop a temp, using:
> 
>         tcg_gen_movcond_i64(TCG_COND_NE, cpu_SR[SR_PC],
>                             tmp_btaken, cpu_R[0],
>                             pc_true, pc_false);
> 
> >> +
> >> +    tcg_temp_free_i64(tmp_btaken);
> >> +    tcg_temp_free_i64(tmp_zero);
> >>  }
> >>  
> >>  static void dec_bcc(DisasContext *dc)
> >>