[Bug ipa/107931] [12/13 Regression] -Og causes always_inline to fail since r12-6677-gc952126870c92cf2

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107931

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
   Target Milestone|---                         |12.3
                 CC|                            |hubicka at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
always-inline and indirect function calls do not mix well, whether they are
inlined or not depends on what optimization is performed.

The re-ordering fixes things because the topological ordering of functions
for the early inlining "breaks" for indirect call edges (I wonder if we can
try to conservatively assume address-takens as calls here?)

It's considered a user error when at IPA time not all always-inline functions
are inlined.

The regression happens because we do not special-case always_inline.  With -O0
fun4 isn't inlined either but we do not diagnose that since the call
doesn't end up direct and we sofar refrain from not outputting the body
of fun4, making this a link error at -O0.

fun2:
.LFB1:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        subq    $16, %rsp
        movq    $fun4, -8(%rbp)
        movq    -8(%rbp), %rax
        call    *%rax

IMHO there's nothing to fix here.  Don't use always-inline if you have
indirect calls.