[Bug rtl-optimization/104438] Combine optimization opportunity exposed after pro_and_epilogue

["crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104438

--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> ---
> It is unclear why the CFG wasn't straightened out here.  Is the bb commented
> as "asm" actually asm?  Then GCC will not see it is very cheap/small, yeah.

"asm" is not inline assembly. it's BB 6 below

(note 89 88 126 6 [bb 6] NOTE_INSN_BASIC_BLOCK)
(call_insn 126 89 121 6 (parallel [
            (call (mem:QI (const_int 0 [0]) [0  S1 A8])
                (const_int 0 [0]))
            (unspec [
                    (const_int 1 [0x1])
                ] UNSPEC_CALLEE_ABI)
        ]) -1
     (expr_list:REG_EH_REGION (const_int -2147483648 [0xffffffff80000000])
        (nil))
    (nil))
(jump_insn 121 126 122 6 (set (pc)
        (label_ref 91)) 892 {jump}
     (nil)
 -> 91)
(barrier 122 121 112)
(code_label 112 122 111 7 4 (nil) [1 uses])
(note 111 112 11 7 [bb 7] NOTE_INSN_BASIC_BLOCK)
(insn 11 111 12 7 (set (reg:V8SI 20 xmm0 [orig:131 _168 ] [131])
        (const_vector:V8SI [
                (const_int 0 [0]) repeated x8
            ])) "test.c":28:19 1696 {movv8si_internal}
     (nil))
(insn 12 11 91 7 (set (reg/v:V4DI 23 xmm3 [orig:87 ymm ] [87])
        (const_vector:V4DI [
                (const_int 0 [0]) repeated x4
            ])) "test.c":24:19 1699 {movv4di_internal}
     (nil))
(code_label 91 12 92 8 2 (nil) [1 uses])
(note 92 91 94 8 [bb 8] NOTE_INSN_BASIC_BLOCK)
(insn 94 92 99 8 (set (reg:V2DI 23 xmm3 [176])
        (vec_select:V2DI (reg/v:V4DI 23 xmm3 [orig:87 ymm ] [87])
            (parallel [
                    (const_int 2 [0x2])
                    (const_int 3 [0x3])
                ]))) "{vec_extract_hi_v4di}
     (nil))
(insn 99 94 127 8 (set (reg:V4SI 20 xmm0 [180])
        (plus:V4SI (reg:V4SI 20 xmm0 [178])
            (reg:V4SI 23 xmm3 [176]))) " {*addv4si3}
     (nil))
(insn 127 99 107 8 (set (reg:SI 0 ax [181])
        (reg:SI 20 xmm0 [180])) " {*movsi_internal}
     (nil))
(insn 107 127 123 8 (use (reg/i:SI 0 ax)) "test.c":40:1 -1
     (nil))
(note 123 107 0 NOTE_INSN_DELETED)