On Thu, 18 Apr 2024, Jakub Jelinek wrote:
> Hi!
>
> __builtin_{add,sub,mul}_overflow{,_p} builtins are well defined
> for all inputs even for -ftrapv, and the -fsanitize=signed-integer-overflow
> ifns shouldn't abort in libgcc but emit the desired ubsan diagnostics
> or abort depending on -fsanitize* setting regardless of -ftrapv.
> The expansion of these internal functions uses expand_expr* in various
> places (e.g. MULT_EXPR at least in 2 spots), so temporarily disabling
> flag_trapv in all those spots would be hard.
> The following patch disables it around the bodies of 3 functions
> which can do the expand_expr calls.
> If it was in the C++ FE, I'd use some RAII sentinel, but I don't think
> we have one in the middle-end.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2024-04-18 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/114753
> * internal-fn.cc (expand_mul_overflow): Save flag_trapv and
> temporarily clear it for the duration of the function, then
> restore previous value.
> (expand_vector_ubsan_overflow): Likewise.
> (expand_arith_overflow): Likewise.
>
> * gcc.dg/pr114753.c: New test.
>
> --- gcc/internal-fn.cc.jj 2024-03-23 08:22:50.490607002 +0100
> +++ gcc/internal-fn.cc 2024-04-17 13:44:21.673594413 +0200
> @@ -1631,7 +1631,11 @@ expand_mul_overflow (location_t loc, tre
> rtx target = NULL_RTX;
> signop sign;
> enum insn_code icode;
> + int save_flag_trapv = flag_trapv;
>
> + /* We don't want any __mulv?i3 etc. calls from the expansion of
> + these internal functions, so disable -ftrapv temporarily. */
> + flag_trapv = 0;
> done_label = gen_label_rtx ();
> do_error = gen_label_rtx ();
>
> @@ -2479,6 +2483,7 @@ expand_mul_overflow (location_t loc, tre
> else
> expand_arith_overflow_result_store (lhs, target, mode, res);
> }
> + flag_trapv = save_flag_trapv;
> }
>
> /* Expand UBSAN_CHECK_* internal function if it has vector operands. */
> @@ -2499,7 +2504,11 @@ expand_vector_ubsan_overflow (location_t
> rtx resvr = NULL_RTX;
> unsigned HOST_WIDE_INT const_cnt = 0;
> bool use_loop_p = (!cnt.is_constant (&const_cnt) || const_cnt > 4);
> + int save_flag_trapv = flag_trapv;
>
> + /* We don't want any __mulv?i3 etc. calls from the expansion of
> + these internal functions, so disable -ftrapv temporarily. */
> + flag_trapv = 0;
> if (lhs)
> {
> optab op;
> @@ -2629,6 +2638,7 @@ expand_vector_ubsan_overflow (location_t
> }
> else if (resvr)
> emit_move_insn (lhsr, resvr);
> + flag_trapv = save_flag_trapv;
> }
>
> /* Expand UBSAN_CHECK_ADD call STMT. */
> @@ -2707,7 +2717,11 @@ expand_arith_overflow (enum tree_code co
> prec0 = MIN (prec0, pr);
> pr = get_min_precision (arg1, uns1_p ? UNSIGNED : SIGNED);
> prec1 = MIN (prec1, pr);
> + int save_flag_trapv = flag_trapv;
>
> + /* We don't want any __mulv?i3 etc. calls from the expansion of
> + these internal functions, so disable -ftrapv temporarily. */
> + flag_trapv = 0;
> /* If uns0_p && uns1_p, precop is minimum needed precision
> of unsigned type to hold the exact result, otherwise
> precop is minimum needed precision of signed type to
> @@ -2748,6 +2762,7 @@ expand_arith_overflow (enum tree_code co
> ops.location = loc;
> rtx tem = expand_expr_real_2 (&ops, NULL_RTX, mode, EXPAND_NORMAL);
> expand_arith_overflow_result_store (lhs, target, mode, tem);
> + flag_trapv = save_flag_trapv;
> return;
> }
>
> @@ -2771,6 +2786,7 @@ expand_arith_overflow (enum tree_code co
> if (integer_zerop (arg0) && !unsr_p)
> {
> expand_neg_overflow (loc, lhs, arg1, false, NULL);
> + flag_trapv = save_flag_trapv;
> return;
> }
> /* FALLTHRU */
> @@ -2781,6 +2797,7 @@ expand_arith_overflow (enum tree_code co
> case MULT_EXPR:
> expand_mul_overflow (loc, lhs, arg0, arg1, unsr_p,
> unsr_p, unsr_p, false, NULL);
> + flag_trapv = save_flag_trapv;
> return;
> default:
> gcc_unreachable ();
> @@ -2826,6 +2843,7 @@ expand_arith_overflow (enum tree_code co
> else
> expand_mul_overflow (loc, lhs, arg0, arg1, unsr_p,
> uns0_p, uns1_p, false, NULL);
> + flag_trapv = save_flag_trapv;
> return;
> }
>
> --- gcc/testsuite/gcc.dg/pr114753.c.jj 2024-04-17 13:55:16.246482369
> +0200
> +++ gcc/testsuite/gcc.dg/pr114753.c 2024-04-17 13:54:14.035352376 +0200
> @@ -0,0 +1,14 @@
> +/* PR middle-end/114753 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -ftrapv" } */
> +
> +int
> +main ()
> +{
> + volatile long long i = __LONG_LONG_MAX__;
> + volatile long long j = 2;
> + long long k;
> + if (!__builtin_mul_overflow (i, j, &k) || k != -2LL)
> + __builtin_abort ();
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
