On Thu, 25 Jan 2024, Jakub Jelinek wrote:
> Hi!
>
> The following patch is miscompiled, because convert_to_integer_1 for
> LSHIFT_EXPR tests if the INTEGER_CST shift count is too high, but
> incorrectly compares it against TYPE_SIZE rather than TYPE_PRECISION.
> The type in question is unsigned _BitInt(1), which has TYPE_PRECISION 1,
> TYPE_SIZE 8, and the shift count is 2 in that case.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2024-01-25 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/113574
> * convert.cc (convert_to_integer_1) <case LSHIFT_EXPR>: Compare shift
> count against TYPE_PRECISION rather than TYPE_SIZE.
>
> * gcc.dg/torture/bitint-52.c: New test.
>
> --- gcc/convert.cc.jj 2024-01-03 11:51:24.000000000 +0100
> +++ gcc/convert.cc 2024-01-24 17:29:56.328124611 +0100
> @@ -762,7 +762,8 @@ convert_to_integer_1 (tree type, tree ex
> {
> /* If shift count is less than the width of the truncated type,
> really shift. */
> - if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
> + if (wi::to_widest (TREE_OPERAND (expr, 1))
> + < TYPE_PRECISION (type))
> /* In this case, shifting is like multiplication. */
> goto trunc1;
> else
> --- gcc/testsuite/gcc.dg/torture/bitint-52.c.jj 2024-01-24
> 17:33:42.174986825 +0100
> +++ gcc/testsuite/gcc.dg/torture/bitint-52.c 2024-01-24 17:33:33.395108814
> +0100
> @@ -0,0 +1,23 @@
> +/* PR middle-end/113574 */
> +/* { dg-do run { target bitint } } */
> +/* { dg-options "-std=c23 -pedantic-errors" } */
> +/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */
> +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
> +
> +unsigned _BitInt(1) a;
> +unsigned _BitInt(8) b;
> +
> +void
> +foo (unsigned _BitInt(16) x)
> +{
> + a += (x << 2) | b;
> +}
> +
> +int
> +main ()
> +{
> + foo (0xfef1uwb);
> + if (a)
> + __builtin_abort ();
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
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