toplev.c: Question on __gnu_lto markers in .comm

[Georg-Johann Lay]

toplev.c emits __gnu_lto markers to assembler:

  /* Emit LTO marker if LTO info has been previously emitted.  This is
     used by collect2 to determine whether an object file contains IL.
     We used to emit an undefined reference here, but this produces
     link errors if an object file with IL is stored into a shared
     library without invoking lto1.  */
  if (flag_generate_lto)
    {
#if defined ASM_OUTPUT_ALIGNED_DECL_COMMON
      ASM_OUTPUT_ALIGNED_DECL_COMMON (asm_out_file, NULL_TREE,
                                      "__gnu_lto_v1",
                                      (unsigned HOST_WIDE_INT) 1, 8);
#elif defined ASM_OUTPUT_ALIGNED_COMMON
      ASM_OUTPUT_ALIGNED_COMMON (asm_out_file, "__gnu_lto_v1",
                                 (unsigned HOST_WIDE_INT) 1, 8);
#else
      ASM_OUTPUT_COMMON (asm_out_file, "__gnu_lto_v1",
                         (unsigned HOST_WIDE_INT) 1,
                         (unsigned HOST_WIDE_INT) 1);
#endif

...

Am I right that this is just used as marker for linker/lto1 to detect presence
and style of IL representation?

Background is as follows:

A trivial program, compiled for avr and without LTO, at the and of assembler
output there is

        .ident  "GCC: (GNU) 4.7.0 20120220 (experimental)"

whereas with the LTO there is:

        .comm   __gnu_lto_v1,1,1
        .ident  "GCC: (GNU) 4.7.0 20120220 (experimental)"
.global __do_clear_bss

avr only supports static linking.

The avr backend thinks that the symbol occupies space on the silicon and needs
to be allocated and initialized so that a part of the startup code is dragged
in which is not needed.

Is it always save to ignore __gnu_lto_* symbols when deciding which parts of
startup code are needed?

Thanks,

Johann