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Mailing lists / fpc-devel / 2018-11

Re: The 15k bounty: Optimizing executable speed forLinux x86 / LLVM

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J. Gareth Moreton

At the moment, I'm experimenting with overhauling the x86_64 optimizer to see if I can reduce the number of passes through a block of code - my hope is to greatly increase the speed of the compiler without sacrificing the optimisations performed under -O1 and -O2.  At present, I've attempted to not modify i386 because I wish to use it as a control case (i.e. do my changes break other platforms?)

It's probably not worthy of the bounty, but I'm enjoying the challenge to seeing if I can improve the overall speed in places. Gareth aka. Kit

On Fri 16/11/18 22:58 , "Florian Klämpfl" sent:

Florian Klämpfl wrote
Am 16.11.2018 um 23:36 schrieb Jonas Maebe: > On 16/11/18 22:44, Florian Klämpfl wrote: >> With some compiler tuning and a few tricks (two changes to the code

and hand-simulated peephole optimizations, but I

>> think these tricks can also the compiler do): > > You can improve performance further by devirtualising all method calls

using wpo. First compile it with -FWvipri.wpo

> -OWDEVIRTCALLS,OPTVMTS and next with -Fwvipri.wpo

-OwDEVIRTCALLS,OPTVMTS (at least on my machine it gives a small boost,

> and makes the results also more stable). > > Since I only have a preliminary llvm version (with Dwarf EH) running on

macOS, I can't provide a direct Kylix

> comparison. The versions below are both x86-64. As mentioned before, a

32 bit FPC/LLVM is still quite a way off.

Show quoted text 5 lines
> > * FPC 3.0.4 -MDelphi -O2 -Fwvipri.wpo -OwDEVIRTCALLS,OPTVMTS: > > $ time ./vipribenchmemcache_nodeps > VipriBenchThreaded - RunningTimeSeconds=5, TestCount=100, StartSeq=0,

NumberOfChannels=6, BufferPackets=5000,

> NumberOfSynchroThreads=4 >

.................................................................................................

Show quoted text 7 lines
> Time: 5016ms = 9669059 pkts/s = 14680 MB/s > > real    0m5.137s > user    0m5.042s > sys    0m0.017s > > FPC 3.3.1 + llvm (clang from Xcode 10.1 with -O3 on FPC-generated llvm

IR) and -Fwvipri.wpo -OwDEVIRTCALLS,OPTVMTS (no

> LLVM link-time optimization): > > $ time ./vipribenchmemcache_nodeps_llvm > VipriBenchThreaded - RunningTimeSeconds=5, TestCount=100, StartSeq=0,

NumberOfChannels=6, BufferPackets=5000,

> NumberOfSynchroThreads=4 >

.................................................................................................................

Show quoted text 26 lines
> Time: 5018ms = 11259466 pkts/s = 17094 MB/s > > real    0m5.161s > user    0m5.060s > sys    0m0.017s > Can you test with FPC 3.1.1 native, -O4 and the following patch: compiler/nmem.pas | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/compiler/nmem.pas b/compiler/nmem.pas index d5c1d85e8f..52add1fd81 100644 --- a/compiler/nmem.pas +++ b/compiler/nmem.pas @@ -1176,7 +1176,7 @@ implementation begin include(flags,nf_write); { see comment in tsubscriptnode.mark_write } - if not(is_implicit_pointer_object_type(left.resultdef)) then + if not(is_implicit_array_pointer(left.resultdef)) then left.mark_write; end; ?

Hmmm, needs a few more of my changes to make work, though it should work if used only with the benchmark.

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