[1/7] tcg: Define "deposit" as an optional operation.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/README    |   14 ++++++++++++++
 tcg/tcg-op.h  |   40 ++++++++++++++++++++++++++++++++++++++++
 tcg/tcg-opc.h |    6 ++++++
 tcg/tcg.c     |   13 +++++++++++++
 4 files changed, 73 insertions(+), 0 deletions(-)

On Fri, Jan 07, 2011 at 02:42:57PM -0800, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/README    |   14 ++++++++++++++
>  tcg/tcg-op.h  |   40 ++++++++++++++++++++++++++++++++++++++++
>  tcg/tcg-opc.h |    6 ++++++
>  tcg/tcg.c     |   13 +++++++++++++
>  4 files changed, 73 insertions(+), 0 deletions(-)
> 
> diff --git a/tcg/README b/tcg/README
> index 68d27ff..ef59070 100644
> --- a/tcg/README
> +++ b/tcg/README
> @@ -285,6 +285,20 @@ the four high order bytes are set to zero.
>  Indicate that the value of t0 won't be used later. It is useful to
>  force dead code elimination.
>  
> +* deposit_i32/i64 dest, t1, t2, loc
> +
> +Deposit T2 as a bitfield into T1, placing the result in DEST.
> +The bitfield is described by LOC, an immediate value:
> +
> +  bits 0:7  - the length of the bitfield
> +  bits 8:15 - the position of the first bit
> +
> +For example, 0x101 indicates a 1-bit field at bit 1.
> +This operation would be equivalent to
> +
> +  dest = (t1 & ~2) | ((t2 << 1) & 2)

I'm being rather picky, but would something like this be better? :-

  For example, 0x804 indicates a 4-bit field starting from bit 8.
  This operation would be equivalent to:

    dest = (t1 & ~(0xf << 8)) | ((t2 << 8) & (0xf << 8))

OTOH, the code in your version was simpler... so maybe 0x201 or 0x102
as a compromise?

I suppose it's unlikely that anyone's really going to need the example
though, so I'm probably fussing too much. :-)

Cheers,

On Fri, Jan 07, 2011 at 02:42:57PM -0800, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  tcg/README    |   14 ++++++++++++++
>  tcg/tcg-op.h  |   40 ++++++++++++++++++++++++++++++++++++++++
>  tcg/tcg-opc.h |    6 ++++++
>  tcg/tcg.c     |   13 +++++++++++++
>  4 files changed, 73 insertions(+), 0 deletions(-)
> 
> diff --git a/tcg/README b/tcg/README
> index 68d27ff..ef59070 100644
> --- a/tcg/README
> +++ b/tcg/README
> @@ -285,6 +285,20 @@ the four high order bytes are set to zero.
>  Indicate that the value of t0 won't be used later. It is useful to
>  force dead code elimination.
>  
> +* deposit_i32/i64 dest, t1, t2, loc
> +
> +Deposit T2 as a bitfield into T1, placing the result in DEST.
> +The bitfield is described by LOC, an immediate value:
> +
> +  bits 0:7  - the length of the bitfield
> +  bits 8:15 - the position of the first bit
> +
> +For example, 0x101 indicates a 1-bit field at bit 1.
> +This operation would be equivalent to
> +
> +  dest = (t1 & ~2) | ((t2 << 1) & 2)
> +
> +

The encoding of the constant part actually doesn't match the one in the
C function where two arguments are separated and not encoded. What about
adding a tcg_gen_op5ii_i32/64 function and having the two arguments
separated?

Also what about a shorter name, like for example 'dep' as it is used on
some architectures.

>  ********* Conditional moves
>  
>  * setcond_i32/i64 cond, dest, t1, t2
> diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
> index 3ee0a58..c5a019a 100644
> --- a/tcg/tcg-op.h
> +++ b/tcg/tcg-op.h
> @@ -2071,6 +2071,44 @@ static inline void tcg_gen_rotri_i64(TCGv_i64 ret, TCGv_i64 arg1, int64_t arg2)
>      }
>  }
>  
> +static inline void tcg_gen_deposit_i32(TCGv_i32 ret, TCGv_i32 arg1,
> +				       TCGv_i32 arg2, unsigned int ofs,
> +				       unsigned int len)
> +{
> +#ifdef TCG_TARGET_HAS_deposit_i32
> +  tcg_gen_op4i_i32(INDEX_op_deposit_i32, ret, arg1, arg2, (ofs << 8) | len);
> +#else
> +  uint32_t mask = (1u << len) - 1;
> +  TCGv_i32 t1 = tcg_temp_new_i32 ();
> +
> +  tcg_gen_andi_i32(t1, arg2, mask);
> +  tcg_gen_shli_i32(t1, t1, ofs);
> +  tcg_gen_andi_i32(ret, arg1, ~(mask << ofs));
> +  tcg_gen_or_i32(ret, ret, t1);
> +
> +  tcg_temp_free_i32(t1);
> +#endif
> +}
> +
> +static inline void tcg_gen_deposit_i64(TCGv_i64 ret, TCGv_i64 arg1,
> +				       TCGv_i64 arg2, unsigned int ofs,
> +				       unsigned int len)
> +{
> +#ifdef TCG_TARGET_HAS_deposit_i64
> +  tcg_gen_op4i_i64(INDEX_op_deposit_i64, ret, arg1, arg2, (ofs << 8) | len);
> +#else
> +  uint64_t mask = (1ull << len) - 1;
> +  TCGv_i64 t1 = tcg_temp_new_i64 ();
> +
> +  tcg_gen_andi_i64(t1, arg2, mask);
> +  tcg_gen_shli_i64(t1, t1, ofs);
> +  tcg_gen_andi_i64(ret, arg1, ~(mask << ofs));
> +  tcg_gen_or_i64(ret, ret, t1);
> +
> +  tcg_temp_free_i64(t1);
> +#endif
> +}
> +
>  /***************************************/
>  /* QEMU specific operations. Their type depend on the QEMU CPU
>     type. */
> @@ -2384,6 +2422,7 @@ static inline void tcg_gen_qemu_st64(TCGv_i64 arg, TCGv addr, int mem_index)
>  #define tcg_gen_rotli_tl tcg_gen_rotli_i64
>  #define tcg_gen_rotr_tl tcg_gen_rotr_i64
>  #define tcg_gen_rotri_tl tcg_gen_rotri_i64
> +#define tcg_gen_deposit_tl tcg_gen_deposit_i64
>  #define tcg_const_tl tcg_const_i64
>  #define tcg_const_local_tl tcg_const_local_i64
>  #else
> @@ -2454,6 +2493,7 @@ static inline void tcg_gen_qemu_st64(TCGv_i64 arg, TCGv addr, int mem_index)
>  #define tcg_gen_rotli_tl tcg_gen_rotli_i32
>  #define tcg_gen_rotr_tl tcg_gen_rotr_i32
>  #define tcg_gen_rotri_tl tcg_gen_rotri_i32
> +#define tcg_gen_deposit_tl tcg_gen_deposit_i32
>  #define tcg_const_tl tcg_const_i32
>  #define tcg_const_local_tl tcg_const_local_i32
>  #endif
> diff --git a/tcg/tcg-opc.h b/tcg/tcg-opc.h
> index 2a98fed..ded6311 100644
> --- a/tcg/tcg-opc.h
> +++ b/tcg/tcg-opc.h
> @@ -78,6 +78,9 @@ DEF(sar_i32, 1, 2, 0, 0)
>  DEF(rotl_i32, 1, 2, 0, 0)
>  DEF(rotr_i32, 1, 2, 0, 0)
>  #endif
> +#ifdef TCG_TARGET_HAS_deposit_i32
> +DEF(deposit_i32, 1, 2, 1, 0)
> +#endif
>  
>  DEF(brcond_i32, 0, 2, 2, TCG_OPF_BB_END | TCG_OPF_SIDE_EFFECTS)
>  #if TCG_TARGET_REG_BITS == 32
> @@ -168,6 +171,9 @@ DEF(sar_i64, 1, 2, 0, 0)
>  DEF(rotl_i64, 1, 2, 0, 0)
>  DEF(rotr_i64, 1, 2, 0, 0)
>  #endif
> +#ifdef TCG_TARGET_HAS_deposit_i64
> +DEF(deposit_i64, 1, 2, 1, 0)
> +#endif
>  
>  DEF(brcond_i64, 0, 2, 2, TCG_OPF_BB_END | TCG_OPF_SIDE_EFFECTS)
>  #ifdef TCG_TARGET_HAS_ext8s_i64
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 5dd6a2c..e95a42f 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -956,6 +956,19 @@ void tcg_dump_ops(TCGContext *s, FILE *outfile)
>                      fprintf(outfile, ",$0x%" TCG_PRIlx, args[k++]);
>                  i = 1;
>                  break;
> +#if defined(TCG_TARGET_HAS_deposit_i32) || defined(TCG_TARGET_HAS_deposit_i64)
> +# ifdef TCG_TARGET_HAS_deposit_i32
> +            case INDEX_op_deposit_i32:
> +# endif
> +# ifdef TCG_TARGET_HAS_deposit_i64
> +            case INDEX_op_deposit_i64:
> +# endif
> +                fprintf(outfile, ",%u,%u", (unsigned)args[k] >> 8,
> +                        (unsigned)args[k] & 0xff);
> +                k++;
> +                i = 1;
> +                break;
> +#endif

Having two constants in the op would avoid this special code.

>              default:
>                  i = 0;
>                  break;
> -- 
> 1.7.2.3
> 
> 
>

On 01/09/2011 01:38 PM, Aurelien Jarno wrote:
> The encoding of the constant part actually doesn't match the one in the
> C function where two arguments are separated and not encoded. What about
> adding a tcg_gen_op5ii_i32/64 function and having the two arguments
> separated?

I certainly didn't want to expose the combined argument to the target
translators.  I had thought that saving some memory by combining the
two constants would be a good idea, but perhaps you're right that it's
overly complicated for the benefit.

> Also what about a shorter name, like for example 'dep' as it is used on
> some architectures.

I suppose.  I thought perhaps that would be too cryptic though.


r~