On Mon, Sep 23, 2019 at 4:17 PM Martin Jambor <mjam...@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 <mjam...@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
>
