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

[David Hildenbrand]

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 <address@hidden>
> ---
>  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

Reviewed-by: David Hildenbrand <address@hidden>

-- 

Thanks,

David / dhildenb