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