On Sun, Oct 16, 2022 at 10:25 PM Eugene Rozenfeld via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> With -gstatement-frontiers we may end up with different IR
> coming from the front end with and without debug information turned on.
> See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100733 for details.
> That may result in differences in discriminator values and -fcompare-debug
> failures.
>
> This patch disables printing of discriminators when the dump is intended
> for -fcompare-debug comparison and reverses the workaround in a test.
I don't think this is the correct approach. -gstatement-frontiers is
known to be
prone to these issues and is the one to blame here. I think the bugs should be
SUSPENDED until -gstatement-frontiers is fixed or at least disabled by default
(IIRC Jakub tried that but failed last time)
> Tested on x86_64-pc-linux-gnu.
>
> gcc/ChangeLog:
> PR debug/107231
> PR debug/107169
> * print-rtl.cc (print_rtx_operand_code_i): Don't print discriminators
> for -fdebug-compare.
>
> gcc/testsuite/ChangeLog:
>
> * c-c++-common/ubsan/pr85213.c: Reverse the workaround for
> discriminators.
> ---
> gcc/print-rtl.cc | 13 ++++++++++---
> gcc/testsuite/c-c++-common/ubsan/pr85213.c | 7 +------
> 2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/gcc/print-rtl.cc b/gcc/print-rtl.cc
> index e115f987173..0476f3d7e79 100644
> --- a/gcc/print-rtl.cc
> +++ b/gcc/print-rtl.cc
> @@ -453,10 +453,17 @@ rtx_writer::print_rtx_operand_code_i (const_rtx in_rtx,
> int idx)
> expanded_location xloc = insn_location (in_insn);
> fprintf (m_outfile, " \"%s\":%i:%i", xloc.file, xloc.line,
> xloc.column);
> - int discriminator = insn_discriminator (in_insn);
> - if (discriminator)
> - fprintf (m_outfile, " discrim %d", discriminator);
>
> + /* Don't print discriminators for -fcompare-debug since the IR
> + coming from the front end may be different with and without
> + debug information turned on. That may result in different
> + discriminator values. */
> + if (!(dump_flags & TDF_COMPARE_DEBUG))
> + {
> + int discriminator = insn_discriminator (in_insn);
> + if (discriminator)
> + fprintf (m_outfile, " discrim %d", discriminator);
> + }
> }
> #endif
> }
> diff --git a/gcc/testsuite/c-c++-common/ubsan/pr85213.c
> b/gcc/testsuite/c-c++-common/ubsan/pr85213.c
> index e903e976f2c..8a6be81d20f 100644
> --- a/gcc/testsuite/c-c++-common/ubsan/pr85213.c
> +++ b/gcc/testsuite/c-c++-common/ubsan/pr85213.c
> @@ -1,11 +1,6 @@
> /* PR sanitizer/85213 */
> /* { dg-do compile } */
> -/* Pass -gno-statement-frontiers to work around
> - https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100733 :
> - without it the IR coming from the front end may be different with and
> without
> - debug information turned on. That may cause e.g., different discriminator
> values
> - and -fcompare-debug failures. */
> -/* { dg-options "-O1 -fsanitize=undefined -fcompare-debug
> -gno-statement-frontiers" } */
> +/* { dg-options "-O1 -fsanitize=undefined -fcompare-debug" } */
>
> int
> foo (int x)
> --
> 2.25.1
