On Wed, Nov 21, 2018 at 12:46 AM Jeff Law <l...@redhat.com> wrote:
>
> On 11/19/18 12:58 PM, Uros Bizjak wrote:
> > Hello!
> >
> > The assert in create_pre_exit at mode-switching.c expects return copy
> > pair with nothing in between. However, the compiler starts mode
> > switching pass with the following sequence:
> >
> > (insn 19 18 16 2 (set (reg:V2SF 21 xmm0)
> > (mem/c:V2SF (plus:DI (reg/f:DI 7 sp)
> > (const_int -72 [0xffffffffffffffb8])) [0 S8 A64]))
> > "pr88070.c":8 1157 {*movv2sf_internal}
> > (nil))
> > (insn 16 19 20 2 (set (reg:V2SF 0 ax [orig:91 <retval> ] [91])
> > (reg:V2SF 0 ax [89])) "pr88070.c":8 1157 {*movv2sf_internal}
> > (nil))
> > (insn 20 16 21 2 (unspec_volatile [
> > (const_int 0 [0])
> > ] UNSPECV_BLOCKAGE) "pr88070.c":8 710 {blockage}
> > (nil))
> > (insn 21 20 23 2 (use (reg:V2SF 21 xmm0)) "pr88070.c":8 -1
> > (nil))
> So I know there's an updated patch. But I thought it might be worth
> mentioning that insn 16 here appears to be a nop-move. Removing it
> might address this instance of the problem, but I doubt it's general
> enough to address any larger issues.
>
> You still might want to investigate why it's still in the IL.
Oh yes, I remember this.
These nop-moves were removed in Vlad's patch [1],[2]:
2013-10-25 Vladimir Makarov <vmaka...@redhat.com>
...
* lra-spills.c (lra_final_code_change): Remove useless move insns.
Which regressed vzeroupper insertion pass [3] that was reported in [4].
The functionality was later reverted in [5]:
2013-10-26 Vladimir Makarov <vmaka...@redhat.com>
Revert:
2013-10-25 Vladimir Makarov <vmaka...@redhat.com>
* lra-spills.c (lra_final_code_change): Remove useless move insns.
Which IMO can be reintroduced back, now that vzeroupper pass works in
a different way. We actually have a couple of tests in place for
PR58679 [6].
[1] https://gcc.gnu.org/ml/gcc-patches/2013-10/msg02208.html
[2] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=204079
[3] https://gcc.gnu.org/ml/gcc-patches/2013-10/msg02225.html
[4] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58679
[5] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=204094
[6] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=204109
Uros.
