On 20/11/18 16:48, Pat Haugen wrote:
On 11/19/18 2:30 PM, Pat Haugen wrote:
This is a follow-up from
https://gcc.gnu.org/ml/gcc-patches/2018-11/msg01525.html
This version introduces an "artificial" property of the dependencies produced in
sched-deps.c that is recorded when they are created due to
MAX_PENDING_LIST_LENGTH
and they are thus ignored in the model_analyze_insns ALAP calculation.
This approach gives most of the benefits of the original patch [1] on aarch64.
I tried it on the cactusADM hot function (bench_staggeredleapfrog2_) on
powerpc64le-unknown-linux-gnu
with -O3 and found that the initial version proposed did indeed increase the
instruction count
and stack space. This version gives a small improvement on powerpc in terms of
instruction count
(number of st* instructions stays the same), so I'm hoping this version
addresses Pat's concerns.
Pat, could you please try this version out if you've got the chance?
I tried the new verison on cactusADM, it's showing a 2% degradation. I've
kicked off a full CPU2006 run just to see if any others are affected.
The other benchmarks were neutral. So the only benchmark showing a change is
the 2% degradation on cactusADM. Comparing the generated .s files for
bench_staggeredleapfrog2_(), there is about a 0.7% increase in load insns and
still the 1% increase in store insns.
Sigh :(
What options are you compiling with? I tried a powerpc64le compiler with plain
-O3 and saw got a slight improvement (by manual expection)
Thanks,
Kyrill
-Pat
