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

[crazylht at gmail dot com via Gcc-bugs]

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

--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Hongtao.liu from comment #4)
> > 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))

According to PR104441, vzeroupper shouldn't be inserted here, after fix of
PR104441, CFG wasn't straightened.