[Gambas-user] New JIT Compiler

[Jussi Lahtinen]

Great work guys!

Documentation still contains following sentence:
"Gambas <http://gambasdoc.org/help/def/gambas> is an interpreted language,
with no "just-in-time" or other compilation to native code at all."

http://gambasdoc.org/help/doc/benchmark


Jussi





On 24 May 2012 01:39, Benoît Minisini <gambas at ...1...> wrote:

> Le 23/05/2012 22:20, Emil Lenngren a écrit :
> > Hi everybody.
> >
> > I've been working on a JIT-compiler for Gambas for some months, and I'm
> now
> > ready to release an alpha-version in the latest svn of Gambas.
> > The compiler uses LLVM to produce machine code for x86 or x86_64. You
> need
> > LLVM on your computer for it to work, preferably the latest version from
> > svn (3.0 from Ubuntu repos does not seem to work any well). Find more
> > instructions in the README file.
> >
> > To use it, place the word "Fast" at the top of a Gambas Class file, for a
> > class that you want all functions JIT-compiled instead of interpreted.
> (At
> > the moment you cannot make individual functions JIT-compiled, but that is
> > limited by the gbc compiler.)
> >
> > As it takes some milliseconds for LLVM to emit machine code and do
> > optimizations, you should only use it for functions you really need
> > optimizations.
> >
> > As the JIT compiler analyses the whole function before execution starts,
> > some extra type safety is added. In interpreter mode, you can normally do
> > things like:
> > Print "hello"
> > Print 1.3 \ 5
> > and you will first see hello on the screen, and then an error message
> > complaining you can't do integer division on floats.
> > If you run the same function in the JIT compiler, the error message will
> be
> > thrown before execution starts instead, hopefully in order to make
> programs
> > less buggier.
> > As a consequence, you can not have code like "Try Print 1.3 \ 5" either.
> At
> > the moment the incorrect line is reported in the error message...
> >
> > The best speed-ups will be in functions that use a lot of low-level
> > calculations and control flows (except For Each loops), like functions
> that
> > do a lot of math. If the function mostly calls other libraries, you won't
> > see speed-ups either.
> > There are still the same overhead when calling functions, since the
> gambas
> > stack must be maintained as before, to make error handling work.
> > Using Try/Catch is probably slightly slower too because a real exception
> > handler must be set up.
> >
> > Something the LLVM optimizer is very good at is transforming a chain of
> > if-else statements to a jump table, so code like:
> > Select Case x
> >    Case 1:
> >      ..
> >    Case 2:
> >      ..
> >    Case 3:
> >      ..
> > End Select
> > will be much faster than before, so you don't have to use the "On Goto"
> > syntax and a lot of labels. This will produce identical machine code.
> >
> > Most things are implemented, but there are still many bugs to fix.
> > Some of the (so far) unimplemented features are
> > Calling external C libraries (the Extern keyword).
> > The use of "_unknown" special method.
> > IIf and Choose with different argument data types.
> > The possibility to use Component.Load to load functions that are executed
> > right after in the same function.
> > Profiling
> > Breakpoints
> >
> > Some of the benchmarks from http://gambasdoc.org/help/doc/benchmark
> > Polynom: 102.7 seconds to 4.7 seconds
> > Primes: 18.3 seconds to 3.5 seconds
> > Nbody: 16.0 seconds to 1.8 seconds
> >
> > If you are curious and want to see the optimized LLVM IR you can
> uncomment
> > the line M->dump() at the bottom of the jit_codegen.cpp file in
> gb.jit/src.
> >
> > I hope the JIT compiler will be useful for you ;)
> >
> > /Emil
>
> I will put the contents of your mail in the wiki, under /doc/jit. Feel
> free to complete this page!
>
> --
> Benoît Minisini
>
>
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