compiling attached source with -Os causes the ICE, it works ok with -O1 or -O2

=========================
$ x86_64-yoe-linux-musl-gcc -Os b.c -c

b.c:21245:1: error: unrecognizable insn:
21245 | }
      | ^
(insn 58 57 446 6 (parallel [
            (asm_operands/v ("push %0 ; popf") ("") 0 [
                    (mem:DI (plus:DI (mem/c:DI (plus:DI (reg/f:DI 7 sp)
                                    (const_int 8 [0x8])) [27 %sfp+-72 S8 A64])
                            (const_int 8 [0x8])) [16 e_56(D)->irqflags+0 S8 A64])
                ]
                 [
                    (asm_input:DI ("g") b.c:9370)
                ]
                 [] b.c:9370)
            (clobber (mem:BLK (scratch) [0  A8]))
            (clobber (reg:CC 17 flags))
        ]) "b.c":9370:2 -1
     (nil))
during RTL pass: postreload
b.c:21245:1: internal compiler error: in extract_constrain_insn, at recog.c:2670
0x1564e08 internal_error(char const*, ...)
        ???:0
0x60277f fancy_abort(char const*, int, char const*)
        ???:0
0x5dddbe _fatal_insn(char const*, rtx_def const*, char const*, int, char const*)
        ???:0
0x5dddda _fatal_insn_not_found(rtx_def const*, char const*, int, char const*)
        ???:0


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gcc version 11.0.1 20210307 (experimental) (GCC)