Re: [PATCH] gimple-fold: Handle _BitInt in __builtin_clear_padding [PR102989]

[Richard Biener <rguenther@suse.de>]

On Fri, 28 Jul 2023, Jakub Jelinek wrote:

> Hi!
> 
> The comments about _Atomic _BitInt made me figure out I forgot (although
> earlier was planning to do that) to implement __builtin_clear_padding
> support for _BitInt.
> 
> The following patch (incremental to the _BitInt series) does that.

OK.

Thanks,
Richard.

> 2023-07-28  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c/102989
> 	* gimple-fold.cc (clear_padding_unit): Mention in comment that
> 	_BitInt types don't need to fit either.
> 	(clear_padding_bitint_needs_padding_p): New function.
> 	(clear_padding_type_may_have_padding_p): Handle BITINT_TYPE.
> 	(clear_padding_type): Likewise.
> 
> 	* gcc.dg/bitint-16.c: New test.
> 
> --- gcc/gimple-fold.cc.jj	2023-07-11 15:28:54.704679510 +0200
> +++ gcc/gimple-fold.cc	2023-07-28 12:37:18.971789595 +0200
> @@ -4103,8 +4103,8 @@ gimple_fold_builtin_realloc (gimple_stmt
>    return false;
>  }
>  
> -/* Number of bytes into which any type but aggregate or vector types
> -   should fit.  */
> +/* Number of bytes into which any type but aggregate, vector or
> +   _BitInt types should fit.  */
>  static constexpr size_t clear_padding_unit
>    = MAX_BITSIZE_MODE_ANY_MODE / BITS_PER_UNIT;
>  /* Buffer size on which __builtin_clear_padding folding code works.  */
> @@ -4595,6 +4595,26 @@ clear_padding_real_needs_padding_p (tree
>  	  && (fmt->signbit_ro == 79 || fmt->signbit_ro == 95));
>  }
>  
> +/* _BitInt has padding bits if it isn't extended in the ABI and has smaller
> +   precision than bits in limb or corresponding number of limbs.  */
> +
> +static bool
> +clear_padding_bitint_needs_padding_p (tree type)
> +{
> +  struct bitint_info info;
> +  gcc_assert (targetm.c.bitint_type_info (TYPE_PRECISION (type), &info));
> +  if (info.extended)
> +    return false;
> +  scalar_int_mode limb_mode = as_a <scalar_int_mode> (info.limb_mode);
> +  if (TYPE_PRECISION (type) < GET_MODE_PRECISION (limb_mode))
> +    return true;
> +  else if (TYPE_PRECISION (type) == GET_MODE_PRECISION (limb_mode))
> +    return false;
> +  else
> +    return (((unsigned) TYPE_PRECISION (type))
> +	    % GET_MODE_PRECISION (limb_mode)) != 0;
> +}
> +
>  /* Return true if TYPE might contain any padding bits.  */
>  
>  bool
> @@ -4611,6 +4631,8 @@ clear_padding_type_may_have_padding_p (t
>        return clear_padding_type_may_have_padding_p (TREE_TYPE (type));
>      case REAL_TYPE:
>        return clear_padding_real_needs_padding_p (type);
> +    case BITINT_TYPE:
> +      return clear_padding_bitint_needs_padding_p (type);
>      default:
>        return false;
>      }
> @@ -4855,6 +4877,57 @@ clear_padding_type (clear_padding_struct
>        memset (buf->buf + buf->size, ~0, sz);
>        buf->size += sz;
>        break;
> +    case BITINT_TYPE:
> +      {
> +	struct bitint_info info;
> +	gcc_assert (targetm.c.bitint_type_info (TYPE_PRECISION (type), &info));
> +	scalar_int_mode limb_mode = as_a <scalar_int_mode> (info.limb_mode);
> +	if (TYPE_PRECISION (type) <= GET_MODE_PRECISION (limb_mode))
> +	  {
> +	    gcc_assert ((size_t) sz <= clear_padding_unit);
> +	    if ((unsigned HOST_WIDE_INT) sz + buf->size
> +		> clear_padding_buf_size)
> +	      clear_padding_flush (buf, false);
> +	    if (!info.extended
> +		&& TYPE_PRECISION (type) < GET_MODE_PRECISION (limb_mode))
> +	      {
> +		int tprec = GET_MODE_PRECISION (limb_mode);
> +		int prec = TYPE_PRECISION (type);
> +		tree t = build_nonstandard_integer_type (tprec, 1);
> +		tree cst = wide_int_to_tree (t, wi::mask (prec, true, tprec));
> +		int len = native_encode_expr (cst, buf->buf + buf->size, sz);
> +		gcc_assert (len > 0 && (size_t) len == (size_t) sz);
> +	      }
> +	    else
> +	      memset (buf->buf + buf->size, 0, sz);
> +	    buf->size += sz;
> +	    break;
> +	  }
> +	tree limbtype
> +	  = build_nonstandard_integer_type (GET_MODE_PRECISION (limb_mode), 1);
> +	fldsz = int_size_in_bytes (limbtype);
> +	nelts = int_size_in_bytes (type) / fldsz;
> +	for (HOST_WIDE_INT i = 0; i < nelts; i++)
> +	  {
> +	    if (!info.extended
> +		&& i == (info.big_endian ? 0 : nelts - 1)
> +		&& (((unsigned) TYPE_PRECISION (type))
> +		    % TYPE_PRECISION (limbtype)) != 0)
> +	      {
> +		int tprec = GET_MODE_PRECISION (limb_mode);
> +		int prec = (((unsigned) TYPE_PRECISION (type)) % tprec);
> +		tree cst = wide_int_to_tree (limbtype,
> +					     wi::mask (prec, true, tprec));
> +		int len = native_encode_expr (cst, buf->buf + buf->size,
> +					      fldsz);
> +		gcc_assert (len > 0 && (size_t) len == (size_t) fldsz);
> +		buf->size += fldsz;
> +	      }
> +	    else
> +	      clear_padding_type (buf, limbtype, fldsz, for_auto_init);
> +	  }
> +	break;
> +      }
>      default:
>        gcc_assert ((size_t) sz <= clear_padding_unit);
>        if ((unsigned HOST_WIDE_INT) sz + buf->size > clear_padding_buf_size)
> --- gcc/testsuite/gcc.dg/bitint-16.c.jj	2023-07-28 12:47:37.641180784 +0200
> +++ gcc/testsuite/gcc.dg/bitint-16.c	2023-07-28 12:47:30.488280320 +0200
> @@ -0,0 +1,31 @@
> +/* PR c/102989 */
> +/* { dg-do compile { target bitint } } */
> +/* { dg-options "-O2 -std=c2x -pedantic-errors" } */
> +
> +_BitInt(15) a;
> +_BitInt(42) b;
> +#if __BITINT_MAXWIDTH__ >= 115
> +_BitInt(115) c;
> +#endif
> +#if __BITINT_MAXWIDTH__ >= 192
> +_BitInt(192) d;
> +#endif
> +#if __BITINT_MAXWIDTH__ >= 575
> +_BitInt(575) e;
> +#endif
> +
> +int
> +main ()
> +{
> +  __builtin_clear_padding (&a);
> +  __builtin_clear_padding (&b);
> +#if __BITINT_MAXWIDTH__ >= 115
> +  __builtin_clear_padding (&c);
> +#endif
> +#if __BITINT_MAXWIDTH__ >= 192
> +  __builtin_clear_padding (&d);
> +#endif
> +#if __BITINT_MAXWIDTH__ >= 575
> +  __builtin_clear_padding (&e);
> +#endif
> +}
> 
> 	Jakub
> 
> 

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