Re: [Qemu-devel] [PATCH 19/38] tcg: Add support for integer absolute value

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/23/19 8:37 PM, David Hildenbrand wrote:
> On 20.04.19 09:34, Richard Henderson wrote:
>> Remove a function of the same name from target/arm/.
>> Use a branchless implementation of abs that gcc uses for x86.
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>  tcg/tcg-op.h           |  5 +++++
>>  target/arm/translate.c | 10 ----------
>>  tcg/tcg-op.c           | 20 ++++++++++++++++++++
>>  3 files changed, 25 insertions(+), 10 deletions(-)
>>
>> diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
>> index 472b73cb38..660fe205d0 100644
>> --- a/tcg/tcg-op.h
>> +++ b/tcg/tcg-op.h
>> @@ -335,6 +335,7 @@ void tcg_gen_smin_i32(TCGv_i32, TCGv_i32 arg1, TCGv_i32 arg2);
>>  void tcg_gen_smax_i32(TCGv_i32, TCGv_i32 arg1, TCGv_i32 arg2);
>>  void tcg_gen_umin_i32(TCGv_i32, TCGv_i32 arg1, TCGv_i32 arg2);
>>  void tcg_gen_umax_i32(TCGv_i32, TCGv_i32 arg1, TCGv_i32 arg2);
>> +void tcg_gen_abs_i32(TCGv_i32, TCGv_i32);
>>  
>>  static inline void tcg_gen_discard_i32(TCGv_i32 arg)
>>  {
>> @@ -534,6 +535,7 @@ void tcg_gen_smin_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>>  void tcg_gen_smax_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>>  void tcg_gen_umin_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>>  void tcg_gen_umax_i64(TCGv_i64, TCGv_i64 arg1, TCGv_i64 arg2);
>> +void tcg_gen_abs_i64(TCGv_i64, TCGv_i64);
>>  
>>  #if TCG_TARGET_REG_BITS == 64
>>  static inline void tcg_gen_discard_i64(TCGv_i64 arg)
>> @@ -973,6 +975,7 @@ void tcg_gen_nor_vec(unsigned vece, TCGv_vec r, TCGv_vec a, TCGv_vec b);
>>  void tcg_gen_eqv_vec(unsigned vece, TCGv_vec r, TCGv_vec a, TCGv_vec b);
>>  void tcg_gen_not_vec(unsigned vece, TCGv_vec r, TCGv_vec a);
>>  void tcg_gen_neg_vec(unsigned vece, TCGv_vec r, TCGv_vec a);
>> +void tcg_gen_abs_vec(unsigned vece, TCGv_vec r, TCGv_vec a);
>>  void tcg_gen_ssadd_vec(unsigned vece, TCGv_vec r, TCGv_vec a, TCGv_vec b);
>>  void tcg_gen_usadd_vec(unsigned vece, TCGv_vec r, TCGv_vec a, TCGv_vec b);
>>  void tcg_gen_sssub_vec(unsigned vece, TCGv_vec r, TCGv_vec a, TCGv_vec b);
>> @@ -1019,6 +1022,7 @@ void tcg_gen_stl_vec(TCGv_vec r, TCGv_ptr base, TCGArg offset, TCGType t);
>>  #define tcg_gen_addi_tl tcg_gen_addi_i64
>>  #define tcg_gen_sub_tl tcg_gen_sub_i64
>>  #define tcg_gen_neg_tl tcg_gen_neg_i64
>> +#define tcg_gen_abs_tl tcg_gen_abs_i64
>>  #define tcg_gen_subfi_tl tcg_gen_subfi_i64
>>  #define tcg_gen_subi_tl tcg_gen_subi_i64
>>  #define tcg_gen_and_tl tcg_gen_and_i64
>> @@ -1131,6 +1135,7 @@ void tcg_gen_stl_vec(TCGv_vec r, TCGv_ptr base, TCGArg offset, TCGType t);
>>  #define tcg_gen_addi_tl tcg_gen_addi_i32
>>  #define tcg_gen_sub_tl tcg_gen_sub_i32
>>  #define tcg_gen_neg_tl tcg_gen_neg_i32
>> +#define tcg_gen_abs_tl tcg_gen_abs_i32
>>  #define tcg_gen_subfi_tl tcg_gen_subfi_i32
>>  #define tcg_gen_subi_tl tcg_gen_subi_i32
>>  #define tcg_gen_and_tl tcg_gen_and_i32
>> diff --git a/target/arm/translate.c b/target/arm/translate.c
>> index 83a008e945..721171794d 100644
>> --- a/target/arm/translate.c
>> +++ b/target/arm/translate.c
>> @@ -603,16 +603,6 @@ static void gen_sar(TCGv_i32 dest, TCGv_i32 t0, TCGv_i32 t1)
>>      tcg_temp_free_i32(tmp1);
>>  }
>>  
>> -static void tcg_gen_abs_i32(TCGv_i32 dest, TCGv_i32 src)
>> -{
>> -    TCGv_i32 c0 = tcg_const_i32(0);
>> -    TCGv_i32 tmp = tcg_temp_new_i32();
>> -    tcg_gen_neg_i32(tmp, src);
>> -    tcg_gen_movcond_i32(TCG_COND_GT, dest, src, c0, src, tmp);
>> -    tcg_temp_free_i32(c0);
>> -    tcg_temp_free_i32(tmp);
>> -}
>> -
>>  static void shifter_out_im(TCGv_i32 var, int shift)
>>  {
>>      if (shift == 0) {
>> diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
>> index a00d1df37e..0ac291f1c4 100644
>> --- a/tcg/tcg-op.c
>> +++ b/tcg/tcg-op.c
>> @@ -1091,6 +1091,16 @@ void tcg_gen_umax_i32(TCGv_i32 ret, TCGv_i32 a, TCGv_i32 b)
>>      tcg_gen_movcond_i32(TCG_COND_LTU, ret, a, b, b, a);
>>  }
>>  
>> +void tcg_gen_abs_i32(TCGv_i32 ret, TCGv_i32 a)
>> +{
>> +    TCGv_i32 t = tcg_temp_new_i32();
>> +
>> +    tcg_gen_sari_i32(t, a, 31);
>> +    tcg_gen_xor_i32(ret, a, t);
>> +    tcg_gen_sub_i32(ret, ret, t);
>> +    tcg_temp_free_i32(t);
>> +}
>> +
>>  /* 64-bit ops */
>>  
>>  #if TCG_TARGET_REG_BITS == 32
>> @@ -2548,6 +2558,16 @@ void tcg_gen_umax_i64(TCGv_i64 ret, TCGv_i64 a, TCGv_i64 b)
>>      tcg_gen_movcond_i64(TCG_COND_LTU, ret, a, b, b, a);
>>  }
>>  
>> +void tcg_gen_abs_i64(TCGv_i64 ret, TCGv_i64 a)
>> +{
>> +    TCGv_i64 t = tcg_temp_new_i64();
>> +
>> +    tcg_gen_sari_i64(t, a, 63);
>> +    tcg_gen_xor_i64(ret, a, t);
>> +    tcg_gen_sub_i64(ret, ret, t);
>> +    tcg_temp_free_i64(t);
>> +}
>> +
>>  /* Size changing operations.  */
>>  
>>  void tcg_gen_extrl_i64_i32(TCGv_i32 ret, TCGv_i64 arg)
>>
> 
> Nice trick

Per commit 7dcfb0897b99, I think it's worth a:

Inspired-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>

> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
>