[fpc-devel] The 15k bounty: Optimizing executable speed for Linux x86 / LLVM

[Florian Klämpfl]

Am 16.11.2018 um 23:41 schrieb Florian Klämpfl:
> 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.
>>
>> * 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
>> .................................................................................................
>> 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
>> .................................................................................................................
>> 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.