On Fri, 1 Dec 2023, Jakub Jelinek wrote:
> Hi!
>
> handle_operand_addr for INTEGER_CSTs uses wi::min_precision (UNSIGNED
> for non-negative constants, SIGNED for negative ones) and from that
> computes mp as minimum number of limbs which can represent that value,
> and in some cases creates a test BITINT_TYPE with that precision to
> categorize it and decide based on that what types to use on the constant
> emitted into memory. For the actual precisions (what will be passed
> to libgcc) it actually already uses MAX/MIN to adjust the corner cases:
> *prec = MAX (min_prec, 1);
> ...
> *prec = MIN ((int) -min_prec, -2);
> but for integer_zerop min_prec will be 0,
> mp = CEIL (min_prec, limb_prec) * limb_prec;
> will be also 0 and we ICE trying to build unsigned BITINT_TYPE with
> 0 precision.
>
> Fixed thusly by noting even 0 has to be encoded at least as one limb.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2023-12-01 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/112771
> * gimple-lower-bitint.cc (bitint_large_huge::handle_operand_addr):
> Use mp = limb_prec if it is zero.
>
> * gcc.dg/bitint-44.c: New test.
>
> --- gcc/gimple-lower-bitint.cc.jj 2023-11-30 17:24:59.828026693 +0100
> +++ gcc/gimple-lower-bitint.cc 2023-11-30 17:42:07.172487347 +0100
> @@ -2179,6 +2179,8 @@ bitint_large_huge::handle_operand_addr (
> *prec = MIN ((int) -min_prec, -2);
> }
> mp = CEIL (min_prec, limb_prec) * limb_prec;
> + if (mp == 0)
> + mp = limb_prec;
> if (mp >= (unsigned) TYPE_PRECISION (TREE_TYPE (op)))
> type = TREE_TYPE (op);
> else
> --- gcc/testsuite/gcc.dg/bitint-44.c.jj 2023-11-30 17:45:02.421017172
> +0100
> +++ gcc/testsuite/gcc.dg/bitint-44.c 2023-11-30 17:39:51.968393081 +0100
> @@ -0,0 +1,10 @@
> +/* PR middle-end/112771 */
> +/* { dg-do compile { target bitint575 } } */
> +/* { dg-options "-std=c23" } */
> +
> +_BitInt(575)
> +foo (_BitInt(575) a)
> +{
> + a /= 0; /* { dg-warning "division by zero" } */
> + return a;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
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