Re: [PATCH V2] SCCVN: Add LEN_MASK_STORE and fix LEN_STORE

[Richard Biener <rguenther@suse.de>]

On Mon, 26 Jun 2023, juzhe.zhong@rivai.ai wrote:

> From: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>
> 
> Hi, Richi. It seems that we use nunits which is len + bias to iterate then we can
> simplify the codes.
> 
> Also, I fixed behavior of len_store,
> 
> Before this patch:
>    (len - bias) * BITS_PER_UNIT
> After this patch:
>    (len + bias) * BITS_PER_UNIT
>    
> gcc/ChangeLog:
> 
>         * tree-ssa-sccvn.cc (vn_reference_lookup_3): Add LEN_MAS_STORE and fix LEN_STORE.
> 
> ---
>  gcc/tree-ssa-sccvn.cc | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
> index 11061a374a2..228ec117ff3 100644
> --- a/gcc/tree-ssa-sccvn.cc
> +++ b/gcc/tree-ssa-sccvn.cc
> @@ -3304,6 +3304,16 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
>  	  if (!tree_fits_uhwi_p (len) || !tree_fits_shwi_p (bias))
>  	    return (void *)-1;
>  	  break;
> +	case IFN_LEN_MASK_STORE:
> +	  len = gimple_call_arg (call, 2);
> +	  bias = gimple_call_arg (call, 5);
> +	  if (!tree_fits_uhwi_p (len) || !tree_fits_shwi_p (bias))
> +	    return (void *)-1;
> +	  mask = gimple_call_arg (call, internal_fn_mask_index (fn));
> +	  mask = vn_valueize (mask);
> +	  if (TREE_CODE (mask) != VECTOR_CST)
> +	    return (void *)-1;
> +	  break;
>  	default:
>  	  return (void *)-1;
>  	}
> @@ -3344,6 +3354,11 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
>  	      tree vectype = TREE_TYPE (def_rhs);
>  	      unsigned HOST_WIDE_INT elsz
>  		= tree_to_uhwi (TYPE_SIZE (TREE_TYPE (vectype)));
> +	      poly_uint64 nunits;
> +	      if (len)
> +		nunits = tree_to_uhwi (len) + tree_to_shwi (bias);
> +	      else
> +		nunits = TYPE_VECTOR_SUBPARTS (vectype);

Are the _LEN ifns accessible via intrinsics as well?  If so I think
we should use MIN (nunits, len + bias) here as otherwise we risk
out-of bound accesses.

Otherwise looks good to me.

Thanks,
Richard.

>  	      if (mask)
>  		{
>  		  HOST_WIDE_INT start = 0, length = 0;
> @@ -3373,7 +3388,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
>  			length += elsz;
>  		      mask_idx++;
>  		    }
> -		  while (known_lt (mask_idx, TYPE_VECTOR_SUBPARTS (vectype)));
> +		  while (known_lt (mask_idx, nunits));
>  		  if (length != 0)
>  		    {
>  		      pd.rhs_off = start;
> @@ -3389,7 +3404,7 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_,
>  		{
>  		  pd.offset = offset2i;
>  		  pd.size = (tree_to_uhwi (len)
> -			     + -tree_to_shwi (bias)) * BITS_PER_UNIT;
> +			     + tree_to_shwi (bias)) * BITS_PER_UNIT;
>  		  if (BYTES_BIG_ENDIAN)
>  		    pd.rhs_off = pd.size - tree_to_uhwi (TYPE_SIZE (vectype));
>  		  else
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)