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.

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

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