[Bug target/116512] [12/13/14/15 Regression] vzeroupper emitted even though the upper half of the z registers are returned

[liuhongt at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116512

--- Comment #6 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> (In reply to Hongtao Liu from comment #4)
> > gdb shows crtl->return_rtx is
> > 
> > 21(parallel/i:BLK [                                                         
> > 
> > 22        (expr_list:REG_DEP_TRUE (reg:XI 20 xmm0)                          
> > 
> > 23            (const_int 0 [0]))                                            
> > 
> > 24    ])
> 
> Oh, so ix86_avx_u128_mode_exit does not understand parallel here.

For function arguments/return, when it's BLK mode, it's put in parallel with an
expr_list which needs extra handle.