[Bug c/84100] New: Function __attribute__((optimize(align-loops=32))) gives spurious warning

["gcc at gmch dot uk" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84100

            Bug ID: 84100
           Summary: Function __attribute__((optimize(align-loops=32)))
                    gives spurious warning
           Product: gcc
           Version: 7.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at gmch dot uk
  Target Milestone: ---

With v7.2.1, compiling for recent x86_64, the command line option
"-falign-loops=32" is accepted and has the desired effect.

However I find that both:

    _Pragma("GCC optimize(\"align-loops=32\")")

and:

    __attribute__((optimize("align-loops=32")))

are rejected with a "warning: bad option '-falign-loops=32'" -- reported for
each and every affected function.

I have tried optimize("align-loops=x") for x=0, 1, 8 and 16 -- all are rejected
the same way.

FWIW, brief checks with Compiler Explorer suggest:

  1) this appears to be a new bug in v7, or at least
     since v6.3.

  2) v6.3 accepts the _Pragma(), but does *not* do the requested
     alignment.

  3) v5.4 accepts the _Pragma(), and does the requested alignment.

Chris