UNSPEC related notes and libbacktrace (was: [PATCH] Silence some dwarf2out UNSPEC related notes (PR debug/88723))

[Gerald Pfeifer]

On Mon, 7 Jan 2019, Jakub Jelinek wrote:
> Apparently my recent patch turned on many non-delegitimized UNSPEC notes
> (it is checking only note, goes away in release builds, but anyway).

I've been seeing the following in my testsuite runs which I didn't
get a month or so ago.  Are these due to your changes, Jakub, or 
some changes around libbacktrace?

i586-unknown-freebsd11 (and not on amd64-unknown-freebsd12, so may
be another 32-bit-specific issue)?

/scratch/tmp/gerald/GCC-HEAD/libbacktrace/pecoff.c: In function 'coff_nosyms':
/scratch/tmp/gerald/GCC-HEAD/libbacktrace/pecoff.c:209:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  209 | coff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~
/scratch/tmp/gerald/GCC-HEAD/libbacktrace/pecoff.c: In function 'coff_nosyms':
/scratch/tmp/gerald/GCC-HEAD/libbacktrace/pecoff.c:209:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  209 | coff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~
xcoff_32.c: In function 'xcoff_nosyms':
xcoff_32.c:431:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  431 | xcoff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~~
xcoff_32.c: In function 'xcoff_nosyms':
xcoff_32.c:431:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  431 | xcoff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~~
xcoff_64.c: In function 'xcoff_nosyms':
xcoff_64.c:431:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  431 | xcoff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~~
xcoff_64.c: In function 'xcoff_nosyms':
xcoff_64.c:431:1: note: non-delegitimized UNSPEC UNSPEC_SET_GOT (14) found in variable location
  431 | xcoff_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
      | ^~~~~~~~~~~~

Gerald