Re: Various selective scheduling fixes

[Andrey Belevantsev <abel at ispras dot ru>]

Hi Christophe,

On 01.04.2016 10:33, Christophe Lyon wrote:
> On 31 March 2016 at 16:43, Andrey Belevantsev <abel@ispras.ru> wrote:
> > Hello,
> >
> > On 14.03.2016 12:10, Andrey Belevantsev wrote:
> > > Hello,
> > >
> > > In this thread I will be posting the patches for the fixed selective
> > > scheduling PRs (except the one that was already kindly checked in by
> > > Jeff).
> > >  The patches were tested both on x86-64 and ia64 with the following
> > > combination: 1) the usual bootstrap/regtest, which only utilizes sel-sched
> > > on its own tests, made by default to run on arm/ppc/x86-64/ia64; 2) the
> > > bootstrap/regtest with the second scheduler forced to sel-sched; 3) both
> > > schedulers forced to sel-sched.  In all cases everything seemed to be
> > > fine.
> > >
> > > Three of the PRs are regressions, the other two showed different errors
> > > across the variety of releases tested by submitters;  I think all of them
> > > are appropriate at this stage -- they do not touch anything outside of
> > > selective scheduling except the first patch where a piece of code from
> > > sched-deps.c needs to be refactored into a function to be called from
> > > sel-sched.c.
> >
> >
> > I've backported all regression PRs to gcc-5-branch after testing there again
> > with selective scheduling force enabled: PRs 64411, 66660, 69032, 69102.
> > The first one was not marked as a regression as such but the test for PR
> > 70292, which is duplicate, works for me on gcc 5.1 thus making it a
> > regression, too.
>
> Hi,
>
> The backport for pr69102 shows that the new testcase fails to compile (ICE)
> when GCC is configured as:
>
> --target=arm-none-linux-gnueabihf --with-float=hard --with-mode=arm
> --with-cpu=cortex-a15 --with-fpu=neon-vfpv4
>
> /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.c-torture/compile/pr69102.c:
> In function 'foo':
> /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/testsuite/gcc.c-torture/compile/pr69102.c:21:1:
> internal compiler error: Segmentation fault
> 0xa64d15 crash_signal
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/toplev.c:383
> 0xfa41d7 autopref_multipass_dfa_lookahead_guard(rtx_insn*, int)
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/haifa-sched.c:5752
> 0xa31cd2 invoke_dfa_lookahead_guard
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:4212
> 0xa31cd2 find_best_expr
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:4415
> 0xa343fb fill_insns
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:5570
> 0xa343fb schedule_on_fences
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:7395
> 0xa36010 sel_sched_region_2
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:7533
> 0xa36f2a sel_sched_region_1
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:7575
> 0xa36f2a sel_sched_region(int)
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:7676
> 0xa37589 run_selective_scheduling()
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sel-sched.c:7752
> 0xa14aed rest_of_handle_sched2
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sched-rgn.c:3647
> 0xa14aed execute
>         /aci-gcc-fsf/sources/gcc-fsf/gccsrc/gcc/sched-rgn.c:3791
>
> See http://people.linaro.org/~christophe.lyon/cross-validation/gcc/gcc-5-branch/234625/arm-none-linux-gnueabihf/diff-gcc-rh60-arm-none-linux-gnueabihf-arm-cortex-a15-neon-vfpv4.txt
>
> Can you have a look?

That's because A15 is the only place which enables 
autopref_multipass_dfa_lookahead_guard as the DFA lookahead guard hook. 
But autoprefetch modeling doesn't work for selective scheduling, it uses 
haifa structures that are not kept up to date during sel-sched.  So this is 
not supposed to work as soon as the param value for prefetcher lookahead 
depth is positive.

The following patch works for me.  Could you check it with your testing? 
If it works fine for you, I would install the patch both for trunk and 
gcc-5.  It would be great to force sel-sched to be enabled, too.  I could 
do that but I don't have the hardware or cross-arm target tools at the moment.

        * haifa-sched.c (autopref_multipass_dfa_lookahead_guard): Disable 
for selective scheduler.

Best,
Andrey


> Christophe
>
> > Andrey
> >
> > > Andrey

diff --git a/gcc/haifa-sched.c b/gcc/haifa-sched.c
index ad2450b..c790830 100644
--- a/gcc/haifa-sched.c
+++ b/gcc/haifa-sched.c
@@ -5691,6 +5691,10 @@ autopref_multipass_dfa_lookahead_guard (rtx_insn *insn1, int ready_index)
 {
   int r = 0;
 
+  /* Autoprefetcher modeling is not supported by selective scheduler.  */
+  if (sel_sched_p ())
+    return 0;
+
   if (PARAM_VALUE (PARAM_SCHED_AUTOPREF_QUEUE_DEPTH) <= 0)
     return 0;