[Bug target/84301] [6/7/8 Regression] ICE in create_pre_exit, at mode-switching.c:451

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84301

--- Comment #1 from Uroš Bizjak <ubizjak at gmail dot com> ---
The function should have either be declared void or with a value return.

Otherwise, selective scheduler should be taught to not separate (insn 16) from
its use (insn 19):

...

(insn 17 9 18 2 (clobber (reg/i:SI 0 ax)) "pr84301.c":13 -1
     (nil))
(insn 18 17 16 2 (clobber (reg:SI 0 ax [orig:94 <retval> ] [94]))
"pr84301.c":13 -1
     (nil))
(insn 16 18 10 2 (set (reg/i:SI 0 ax)
        (reg:SI 0 ax [orig:94 <retval> ] [94])) "pr84301.c":13 86
{*movsi_internal}
     (nil))
(insn 10 16 27 2 (parallel [
            (set (reg:DI 2 cx [orig:96 lr ] [96])
                (minus:DI (reg:DI 2 cx [orig:96 lr ] [96])
                    (reg:DI 1 dx [orig:88 _2 ] [88])))
            (clobber (reg:CC 17 flags))
        ]) "pr84301.c":10 278 {*subdi_1}
     (nil))
(insn 27 10 11 2 (set (reg:DI 1 dx [98])
        (reg:DI 2 cx [orig:96 lr ] [96])) "pr84301.c":10 85 {*movdi_internal}
     (nil))
(insn 11 27 19 2 (set (reg:CCGC 17 flags)
        (compare:CCGC (reg:DI 1 dx [98])
            (const_int 1 [0x1]))) "pr84301.c":10 12 {*cmpdi_1}
     (nil))
(insn 19 11 21 2 (use (reg/i:SI 0 ax)) "pr84301.c":13 -1
     (nil))

...

The assert in mode-switching.c is there to catch the above case.

So, probably ice-on-ivalid-code with selective scheduling.