Re: [PR 91832] Do not ICE on negative offsets in ipa-sra

[Richard Biener <richard dot guenther at gmail dot com>]

On Mon, Sep 23, 2019 at 4:17 PM Martin Jambor <mjambor@suse.cz> wrote:
>
> Hi,
>
> IPA-SRA asserts that an offset obtained from get_ref_base_and_extent
> is non-negative (after it verifies it is based on a parameter).  That
> assumption is invalid as the testcase shows.  One could probably also write a
> testcase with defined behavior, but unless I see a reasonable one
> where the transformation is really desirable, I'd like to just punt on
> those cases.
>
> Bootstrapped and tested on x86_64-linux.  OK for trunk?

OK.

Richard.

> Thanks,
>
> Martin
>
> 2019-09-23  Martin Jambor  <mjambor@suse.cz>
>
>         PR ipa/91832
>         * ipa-sra.c (scan_expr_access): Check that offset is non-negative.
>
>         testsuite/
>         * gcc.dg/ipa/pr91832.c: New test.
> ---
>  gcc/ipa-sra.c                      |  7 ++++++-
>  gcc/testsuite/gcc.dg/ipa/pr91832.c | 12 ++++++++++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.dg/ipa/pr91832.c
>
> diff --git a/gcc/ipa-sra.c b/gcc/ipa-sra.c
> index a32defb59bd..0ccebbd4607 100644
> --- a/gcc/ipa-sra.c
> +++ b/gcc/ipa-sra.c
> @@ -1692,7 +1692,12 @@ scan_expr_access (tree expr, gimple *stmt, isra_scan_context ctx,
>        disqualify_split_candidate (desc, "Encountered a bit-field access.");
>        return;
>      }
> -  gcc_assert (offset >= 0);
> +  if (offset < 0)
> +    {
> +      disqualify_split_candidate (desc, "Encountered an access at a "
> +                                 "negative offset.");
> +      return;
> +    }
>    gcc_assert ((offset % BITS_PER_UNIT) == 0);
>    gcc_assert ((size % BITS_PER_UNIT) == 0);
>    if ((offset / BITS_PER_UNIT) >= (UINT_MAX - ISRA_ARG_SIZE_LIMIT)
> diff --git a/gcc/testsuite/gcc.dg/ipa/pr91832.c b/gcc/testsuite/gcc.dg/ipa/pr91832.c
> new file mode 100644
> index 00000000000..4a0d62ec1d9
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/ipa/pr91832.c
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2"  } */
> +
> +struct A1 {
> +  char a1[1];
> +};
> +
> +void fn2(char a);
> +
> +void fn1(struct A1 *p1) {
> +  fn2(p1->a1[-1]);
> +}
> --
> 2.23.0
>