Yes, -gstatement-frontiers is the root cause here but the new approach to discriminators is especially prone to this. I added the workaround to pr85213.c in my original discriminator patch but now two more -fcompare-debug bugs were opened (PR107231 and PR107169). I suspect we'll keep getting more. So I'd like to disable printing discriminators in -fcompare-debug dums until -gstatement-frontier issue is fixed.
Eugene -----Original Message----- From: Richard Biener <richard.guent...@gmail.com> Sent: Monday, October 17, 2022 12:06 AM To: Eugene Rozenfeld <eugene.rozenf...@microsoft.com> Cc: gcc-patches@gcc.gnu.org; Jason Merrill <ja...@redhat.com> Subject: [EXTERNAL] Re: [PATCH] Don't print discriminators for -fcompare-debug. 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://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fbugzilla%2Fshow_bug.cgi%3Fid%3D100733&data=05%7C01%7CEugene.Rozenfeld%40microsoft.com%7C5d3df88ec7e14f5eec2708dab00e0440%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C638015871510301049%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=2JjQHAgDi6%2Fet1vowA1IRcdInJMkkjuva9DbM5rHawc%3D&reserved=0 > 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://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fbugzilla%2Fshow_bug.cgi%3Fid%3D100733&data=05%7C01%7CEugene.Rozenfeld%40microsoft.com%7C5d3df88ec7e14f5eec2708dab00e0440%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C638015871510301049%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=2JjQHAgDi6%2Fet1vowA1IRcdInJMkkjuva9DbM5rHawc%3D&reserved=0 > : > - 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
