Re: [wide-int] Remove SHIFT_COUNT_TRUNCATED uses at tree/gimple level

[Kenneth Zadeck <zadeck at naturalbridge dot com>]

So what is the big plan here?     if you remove it here and then do not 
do it in wide int, then it is not going to be truncated.

kenny


On 11/06/2013 05:10 PM, Richard Sandiford wrote:
> Following the removal of SHIFT_COUNT_TRUNCATED from double-int, this patch
> reverts the changed I'd made to mimic the old behaviour on wide-int.
>
> Tested on powerpc64-linux-gnu and by assembly comparison on a range of targets.
> OK to install?
>
> Thanks,
> Richard
>
>
> Index: gcc/fold-const.c
> ===================================================================
> --- gcc/fold-const.c	2013-11-05 13:06:56.985255941 +0000
> +++ gcc/fold-const.c	2013-11-05 13:12:28.805655903 +0000
> @@ -1007,13 +1007,9 @@ int_const_binop_1 (enum tree_code code,
>   	/* It's unclear from the C standard whether shifts can overflow.
>   	   The following code ignores overflow; perhaps a C standard
>   	   interpretation ruling is needed.  */
> -	res = wi::rshift (arg1, arg2, sign,
> -			  SHIFT_COUNT_TRUNCATED
> -			  ? GET_MODE_BITSIZE (TYPE_MODE (type)) : 0);
> +	res = wi::rshift (arg1, arg2, sign);
>         else
> -	res = wi::lshift (arg1, arg2,
> -			  SHIFT_COUNT_TRUNCATED
> -			  ? GET_MODE_BITSIZE (TYPE_MODE (type)) : 0);
> +	res = wi::lshift (arg1, arg2);
>         break;
>         
>       case RROTATE_EXPR:
> Index: gcc/tree-ssa-ccp.c
> ===================================================================
> --- gcc/tree-ssa-ccp.c	2013-11-05 13:07:25.659474362 +0000
> +++ gcc/tree-ssa-ccp.c	2013-11-05 13:12:28.806655910 +0000
> @@ -1272,20 +1272,15 @@ bit_value_binop_1 (enum tree_code code,
>   		  else
>   		    code = RSHIFT_EXPR;
>   		}
> -	      int shift_precision = SHIFT_COUNT_TRUNCATED ? width : 0;
>   	      if (code == RSHIFT_EXPR)
>   		{
> -		  *mask = wi::rshift (wi::ext (r1mask, width, sgn),
> -				      shift, sgn, shift_precision);
> -		  *val = wi::rshift (wi::ext (r1val, width, sgn),
> -				     shift, sgn, shift_precision);
> +		  *mask = wi::rshift (wi::ext (r1mask, width, sgn), shift, sgn);
> +		  *val = wi::rshift (wi::ext (r1val, width, sgn), shift, sgn);
>   		}
>   	      else
>   		{
> -		  *mask = wi::ext (wi::lshift (r1mask, shift, shift_precision),
> -				   width, sgn);
> -		  *val = wi::ext (wi::lshift (r1val, shift, shift_precision),
> -				  width, sgn);
> +		  *mask = wi::ext (wi::lshift (r1mask, shift), width, sgn);
> +		  *val = wi::ext (wi::lshift (r1val, shift), width, sgn);
>   		}
>   	    }
>   	}