On Tue, 25 Mar 2014, Jakub Jelinek wrote:
> On Tue, Mar 25, 2014 at 10:43:02AM +0100, Richard Biener wrote:
> > Yes, all transforms in fold-const would be invalid if the result doesn't
> > behave in the same way wrt overflow. Thus you really should instrument
> > ABS_EXPR - you can treat it as A > 0 ? A : -A if that simplifies it.
> >
> > I don't like the conditions that disable stuff based on sanitization.
> >
> > Instrumenting ABS_EXPR shouldn't be too difficult.
>
> Ok, here is a patch that does that. Tested on x86_64-linux and i686-linux.
> Ok for trunk?
Ok.
Thanks,
Richard.
> 2014-03-25 Jakub Jelinek <ja...@redhat.com>
>
> PR sanitizer/60636
> * ubsan.c (instrument_si_overflow): Instrument ABS_EXPR.
>
> * c-c++-common/ubsan/pr60636.c: New test.
>
> --- gcc/ubsan.c.jj 2014-03-19 14:44:23.000000000 +0100
> +++ gcc/ubsan.c 2014-03-25 13:00:35.052459078 +0100
> @@ -737,6 +737,21 @@ instrument_si_overflow (gimple_stmt_iter
> gimple_call_set_lhs (g, lhs);
> gsi_replace (&gsi, g, false);
> break;
> + case ABS_EXPR:
> + /* Transform i = ABS_EXPR<u>;
> + into
> + _N = UBSAN_CHECK_SUB (0, u);
> + i = ABS_EXPR<_N>; */
> + a = build_int_cst (lhstype, 0);
> + b = gimple_assign_rhs1 (stmt);
> + g = gimple_build_call_internal (IFN_UBSAN_CHECK_SUB, 2, a, b);
> + a = make_ssa_name (lhstype, NULL);
> + gimple_call_set_lhs (g, a);
> + gimple_set_location (g, gimple_location (stmt));
> + gsi_insert_before (&gsi, g, GSI_SAME_STMT);
> + gimple_assign_set_rhs1 (stmt, a);
> + update_stmt (stmt);
> + break;
> default:
> break;
> }
> --- gcc/testsuite/c-c++-common/ubsan/pr60636.c.jj 2014-03-25
> 12:31:29.458629212 +0100
> +++ gcc/testsuite/c-c++-common/ubsan/pr60636.c 2014-03-25
> 12:31:29.458629212 +0100
> @@ -0,0 +1,15 @@
> +/* PR sanitizer/60636 */
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=undefined" } */
> +
> +volatile long long int a;
> +
> +int
> +main ()
> +{
> + long long int u = -__LONG_LONG_MAX__ - 1;
> + a = u > 0 ? u : -u;
> + return 0;
> +}
> +
> +/* { dg-output "negation of -9223372036854775808 cannot be represented in
> type 'long long int'" } */
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
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