Hi [nataraj@dflyHP ~]$ fpc ttt.pas Free Pascal Compiler version 3.2.2 [2023/07/04] for x86_64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: DragonFly for x86-64 Compiling ttt.pas Linking ttt /usr/local/bin/ld.bfd: warning: /usr/local/lib/fpc/3.2.2/units/x86_64-dragonfly/rtl/prt0.o: missing .note.GNU-stack section implies executable stack /usr/local/bin/ld.bfd: NOTE: This behaviour is deprecated and will be removed in a future version of the linker 121 lines compiled, 14.9 sec [nataraj@dflyHP ~]$ ./ttt Pascal control case: 6.7 ns/call Using LEA instruction: 4.2 ns/call Using ADD instructions: 4.0 ns/call
Nataraj S Narayan Synergy Info Systems Software & Technology Consultants Ettumanoor, INDIA Ph:+91 9443211326 On Sat, Oct 7, 2023 at 9:39 PM J. Gareth Moreton via fpc-devel < fpc-devel@lists.freepascal.org> wrote: > That's interesting; I am interested to see the assembly output for the > Pascal control cases. As for the 64-bit version, that was my fault > since the assembly language is for Microsoft's ABI rather than the > System V ABI, so it was checking a register with an undefined value. > Find attached the fixed test. > > Kit > > P.S. Results on my Intel(R) Core(TM) i7-10750H > > Pascal control case: 2.0 ns/call > Using LEA instruction: 1.7 ns/call > Using ADD instructions: 1.3 ns/call > > On 07/10/2023 16:51, Tomas Hajny via fpc-devel wrote: > > On 2023-10-07 03:57, J. Gareth Moreton via fpc-devel wrote: > > > > > > Hi Kit, > > > >> Do you think this should suffice? Originally it ran for 1,000,000 > >> repetitions but I fear that will take way too long on a 486, so I > >> reduced it to 10,000. > > > > OK, I tried it now. First of all, after turning on the old machine, I > > realized that it wasn't Intel but AMD 486 DX4 - sorry for my bad > > memory. :-( I compiled and ran the test under OS/2 there (I was too > > lazy to boot it to DOS ;-) ), but I assume that it shouldn't make any > > substantial difference. The ADD and LEA results were basically the > > same there, both around 100 ns / call. The Pascal result was around > > twice as long. Interestingly, the Pascal result for FPC 3.2.2 was > > around 10% longer than the same source compiled with FPC 2.0.3 (the > > assembler versions were obviously the same for both FPC versions; I > > tried compiling it also with FPC 1.0.10 and the assembler versions > > were more than three times slower due to missing support for the > > nostackframe directive). > > > > I tested it under the AMD Athlon 1 GHz machine as well and again, the > > results for LEA and ADD are basically equal (both 3.1 ns/call) and the > > result for Pascal slightly more than twice (7.3 ns/call). However, > > rather surprisingly for me, the overall test run was _much_ longer > > there?! Finally, I tried compiling the test on a 64-bit machine (AMD > > A9-9425) with Linux (compiled for 64-bits with FPC 3.2.3 compiled from > > a fresh 3.2 branch). The Pascal version shows about 4 ns/call, but the > > assembler version runs forever - well, certainly much longer than my > > patience lasts. I haven't tried to analyze the reasons, but that's > > what I get. > > > > Tomas > > > > > > > >> > >> On 03/10/2023 06:30, Tomas Hajny via fpc-devel wrote: > >>> On October 3, 2023 03:32:34 +0200, "J. Gareth Moreton via fpc-devel" > >>> <fpc-devel@lists.freepascal.org> wrote: > >>> > >>> > >>> Hii Kit, > >>> > >>>> This is mainly to Florian, but also to anyone else who can answer > >>>> the question - at which point did a complex LEA instruction (using > >>>> all three input operands and some other specific circumstances) get > >>>> slow? Preliminary research suggests the 486 was when it gained > >>>> extra latency, and then Sandy Bridge when it got particularly bad. > >>>> Icy Lake seems to be the architecture where faster LEA instructions > >>>> are reintroduced, but I'm not sure about AMD processors. > >>> I cannot answer your question, but if you prepare a test program, I > >>> can run it on an Intel 486 DX2 100 Mhz and AMD Athlon 1 GHz machines > >>> if it helps you in any way (at least I hope the 486 DX2 machine > >>> should be still able to start ;-) ). > >>> > >>> Tomas > >>> > >>> _______________________________________________ > >>> fpc-devel maillist - fpc-devel@lists.freepascal.org > >>> https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel > >>> > >> _______________________________________________ > >> fpc-devel maillist - fpc-devel@lists.freepascal.org > >> https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel > > _______________________________________________ > > fpc-devel maillist - fpc-devel@lists.freepascal.org > > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel > >_______________________________________________ > fpc-devel maillist - fpc-devel@lists.freepascal.org > https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel >
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