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8281 :: Nimscript produces slower executable

• tsojtsoj (orginal) [2021-07-28T22:27:40+02:00] view original

  Normalley I compile my program with

  
  nim c -d:danger --panics:on --gc:arc -d:useMalloc -d:lto --passL:"-static" --cc:clang --threads:on --run Nalwald.nim
  Run

  Now I tried to write a nimscript for the build process:

  
  task default, "default compile":
      --define:danger
      --panics:on
      --gc:arc
      --define:useMalloc
      --define:lto
      --passL:"-static"
      --cc:clang
      --threads:on
      setCommand "c"
  Run

  If I compile this with "nim default Nalwald.nim" the program is 25% slower that the program I get when compiling with the first above. Also, normally the LTO option improves the performance by roughly 25%. If I remove the line --define:lto from the nimscript the resulting program isn't slower than if compiling with the nimscript with --define:lto. So I suspect the LTO option isn't correctly handled by the nimscript.

  But I am completely new to nimscripts, so my questions is, if I missed something, that would fix this issue, or if I rather should use nim.cfg for now.

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• shirleyquirk (orginal) [2021-07-28T22:47:01+02:00] view original

  d: danger and d: release have no effect in a nim.cfg or a nims because they take effect when the global nim.cfg gets read. cf https://forum.nim-lang.org/t/7931#50523

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• tsojtsoj (orginal) [2021-07-28T23:16:42+02:00] view original

  This doesn't seem to be the reason. If I replace --define:danger with --define:release in the nimscript it becomes significantly slower. (The compiler also says Hint: gc: arc; threads: on; opt: speed; options: -d:danger when I have the danger flag.)

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• shirleyquirk (orginal) [2021-07-29T00:32:39+02:00] view original

  you are correct about that.

  dang.nim

  var s = [0,1,2,3]
  echo s[4]
  Run

  config.nims

  task default,"default compile":
    --define:danger
    --hints:off
    --define:lto
    --genScript:on
    setCommand "c"
  
  task manual,"manual compile":
    --hints:off
    exec "nim c --hints:off -d:danger -d:lto --genScript:on " & projectName() & ".nim"
  
  task lastLine,"print last line":
    --hints:off
    exec "tail -n 1 ~/.cache/nim/" & projectName() & "_r/compile_" & projectName() & ".sh"
  Run

  both compile, so d:danger worked (no bounds checks)

  but:

  
  ❯ nim manual dang.nim && nim lastLine dang.nim
  gcc   -o dang  stdlib_assertions.nim.c.o stdlib_io.nim.c.o stdlib_system.nim.c.o @mdang.nim.c.o    -ldl -flto
  ❯ nim default dang.nim && nim lastLine dang.nim
  gcc   -o dang  stdlib_assertions.nim.c.o stdlib_io.nim.c.o stdlib_system.nim.c.o @mdang.nim.c.o    -ldl
  Run

  lto is not being turned on.

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• tsojtsoj (orginal) [2021-07-29T00:55:26+02:00] view original

  Thanks! I'll open a GitHub issue using your example. The issue with the workaround will be that on Windows it sometimes doesn't work in combination with Clang if I remember correctly (I don't have access to a Windows machine currently). It will work for now, though.

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• Yardanico (orginal) [2021-07-29T11:27:59+02:00] view original

  Since 1.4.8 this is no longer true -both release and danger are special-cased so they work in config files just fine :)

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• SolitudeSF (orginal) [2021-07-29T12:50:50+02:00] view original

  now lto, strip and whatever random passC wrapper needs to be special cased too...

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