On 14/11/16 14:25, Kyrill Tkachov wrote:
On 11/11/16 15:31, Kyrill Tkachov wrote:
On 11/11/16 10:17, Kyrill Tkachov wrote:
On 10/11/16 23:39, Segher Boessenkool wrote:
On Thu, Nov 10, 2016 at 02:42:24PM -0800, Andrew Pinski wrote:
On Thu, Nov 10, 2016 at 6:25 AM, Kyrill Tkachov
I ran SPEC2006 on a Cortex-A72. Overall scores were neutral but there were
some interesting swings.
458.sjeng +1.45%
471.omnetpp +2.19%
445.gobmk -2.01%
On SPECFP:
453.povray +7.00%
Wow, this looks really good. Thank you for implementing this. If I
get some time I am going to try it out on other processors than A72
but I doubt I have time any time soon.
I'd love to hear what causes the slowdown for gobmk as well, btw.
I haven't yet gotten a direct answer for that (through performance analysis
tools)
but I have noticed that load/store pairs are not generated as aggressively as I
hoped.
They are being merged by the sched fusion pass and peepholes (which runs after
this)
but it still misses cases. I've hacked the SWS hooks to generate pairs
explicitly and that
increases the number of pairs and helps code size to boot. It complicates the
logic of
the hooks a bit but not too much.
I'll make those changes and re-benchmark, hopefully that
will help performance.
And here's a version that explicitly emits pairs. I've looked at assembly
codegen on SPEC2006
and it generates quite a few more LDP/STP pairs than the original version.
I kicked off benchmarks over the weekend to see the effect.
Andrew, if you want to try it out (more benchmarking and testing always
welcome) this is the
one to try.
And I discovered over the weekend that gamess and wrf have validation errors.
This version runs correctly.
SPECINT results were fine though and there is even a small overall gain due to
sjeng and omnetpp. However, gobmk still has the regression.
I'll rerun SPECFP with this patch (it's really just a small bugfix over the
previous version)
and get on with analysing gobmk.
After looking at the gobmk performance with performance counters it looks like
more icache pressure.
I see an increase in misses.
This looks to me like an effect of code size increase, though it is not that
large an increase (0.4% with SWS).
Branch mispredicts also go up a bit but not as much as icache misses.
I don't think there's anything we can do here, or at least that this patch can
do about it.
Overall, there's a slight improvement in SPECINT, even with the gobmk
regression and a slightly larger improvement
on SPECFP due to povray.
Segher, one curious artifact I spotted while looking at codegen differences in
gobmk was a case where we fail
to emit load-pairs as effectively in the epilogue and its preceeding basic
block.
So before we had this epilogue:
.L43:
ldp x21, x22, [sp, 16]
ldp x23, x24, [sp, 32]
ldp x25, x26, [sp, 48]
ldp x27, x28, [sp, 64]
ldr x30, [sp, 80]
ldp x19, x20, [sp], 112
ret
and I see this becoming (among numerous other changes in the function):
.L69:
ldp x21, x22, [sp, 16]
ldr x24, [sp, 40]
.L43:
ldp x25, x26, [sp, 48]
ldp x27, x28, [sp, 64]
ldr x23, [sp, 32]
ldr x30, [sp, 80]
ldp x19, x20, [sp], 112
ret
So this is better in the cases where we jump straight into .L43 because we load
fewer registers
but worse when we jump to or fallthrough to .L69 because x23 and x24 are now
restored using two loads
rather than a single load-pair. This hunk isn't critical to performance in
gobmk though.
Given that there is an overall gain is this ok for trunk?
https://gcc.gnu.org/ml/gcc-patches/2016-11/msg01352.html
Thanks,
Kyrill
2016-11-11 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
* config/aarch64/aarch64.h (machine_function): Add
reg_is_wrapped_separately field.
* config/aarch64/aarch64.c (emit_set_insn): Change return type to
rtx_insn *.
(aarch64_save_callee_saves): Don't save registers that are wrapped
separately.
(aarch64_restore_callee_saves): Don't restore registers that are
wrapped separately.
(offset_9bit_signed_unscaled_p, offset_12bit_unsigned_scaled_p,
aarch64_offset_7bit_signed_scaled_p): Move earlier in the file.
(aarch64_get_separate_components): New function.
(aarch64_get_next_set_bit): Likewise.
(aarch64_components_for_bb): Likewise.
(aarch64_disqualify_components): Likewise.
(aarch64_emit_prologue_components): Likewise.
(aarch64_emit_epilogue_components): Likewise.
(aarch64_set_handled_components): Likewise.
(TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS,
TARGET_SHRINK_WRAP_COMPONENTS_FOR_BB,
TARGET_SHRINK_WRAP_DISQUALIFY_COMPONENTS,
TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS,
TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS,
TARGET_SHRINK_WRAP_SET_HANDLED_COMPONENTS): Define.
