This example:

void * foo_ifunc (void) __asm__ ("foo");
void *
__attribute__ ((__optimize__ ("-fno-stack-protector")))
foo_ifunc (void)
{
  return 0;
}

extracted from a glibc test results in:

ifuncmod1.s: Assembler messages:
ifuncmod1.s:122: Error: bad expression
ifuncmod1.s:122: Error: junk at end of line, first unrecognized character is `f'
ifuncmod1.s:123: Error: bad expression
ifuncmod1.s:123: Error: junk at end of line, first unrecognized character is `f'
ifuncmod1.s:126: Error: junk at end of line, first unrecognized character is `*'

when compiled with these flags:

gcc -c -O2 -fstack-protector-strong  -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 --save-temps

The assembler input looks like this:

        .globl  foo
        .type   foo, @function
foo:
.LFB0:
        .cfi_startproc
        xorl    %eax, %eax
        ret
        .cfi_endproc
.LFE0:
        .size   foo, .-foo
        .pushsection .gnu.build.attributes
        .dc.l 6         # size of name
        .dc.l 16        # descsz = sizeof (addresses)
        .dc.l 0x101     # type = FUNC
        .dc.b 0x47, 0x41, 0x2a, 0x2, 0, 0       # name (numeric: -fstack-protector status)
        .dc.b 0, 0      # Padding
        .quad *foo
        .quad *foo_end  # description (symbol name)
        .popsection

*foo_end: