[Bug bootstrap/126526] New: [16, X86] Bootstrap comparison failure!

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126526

            Bug ID: 126526
           Summary: [16, X86] Bootstrap comparison failure!
           Product: gcc
           Version: 16.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: bootstrap
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ojab at ojab dot ru
  Target Milestone: ---

Created attachment 65186
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65186&action=edit
.bad_compare

Linux x86_64, gcc-16.1.0 and `releases/gcc-16` branch
(`f1c1322dca42d88edef68762ab52a4c6aacd218a`) configured with 
`../configure --prefix=/usr --enable-languages=c,c++,go --enable-default-pie
--enable-default-ssp --enable-host-pie --disable-multilib --disable-fixincludes
--with-system-zlib --disable-libssp`
both fails with `Bootstrap comparison failure!` between stages 2 and 3
(`.bad_compare` in the attached file).

It's slightly modified & automated Linux from Scratch build and host is
`x86_64-lfs-linux-gnu`, target is `x86_64-pc-linux-gnu`.
GCC-15.3.0 bootstraps fine with the same scripts.

The minimal diff is for `collect-utils.o` and preprocessed source is the same
for stage 2 and 3.

AFAICS all the failures are in debug sections, diff (`objdump -xD`):
```diff
diff --git a/tmp/2 b/tmp/3
index b88a8659141..9af1d399233 100644
--- a/tmp/2
+++ b/tmp/3
@@ -1,6 +1,6 @@

-gcc-16.1.1/build/stage2-gcc/collect-utils.o:     file format elf64-x86-64
-gcc-16.1.1/build/stage2-gcc/collect-utils.o
+gcc-16.1.1/build/stage3-gcc/collect-utils.o:     file format elf64-x86-64
+gcc-16.1.1/build/stage3-gcc/collect-utils.o
 architecture: i386:x86-64, flags 0x00000011:
 HAS_RELOC, HAS_SYMS
 start address 0x0000000000000000
@@ -22855,9 +22855,9 @@ Disassembly of section .debug_loclists:
        ...
                        63c: R_X86_64_64        .text+0x710
  644:  04 00                   add    $0x0,%al
- 646:  1f                      (bad)  
- 647:  01 55 04                add    %edx,0x4(%rbp)
- 64a:  1f                      (bad)  
+ 646:  14 01                   adc    $0x1,%al
+ 648:  55                      push   %rbp
+ 649:  04 14                   add    $0x14,%al
  64b:  20 04 a3                and    %al,(%rbx,%riz,4)
  64e:  01 55 9f                add    %edx,-0x61(%rbp)
  651:  00 01                   add    %al,(%rcx)
```