Re: [ANN] llvm-lua 0.2

["Bogdan Marinescu" <bogdan.marinescu@...>]

Wow, this is very interesting, congratulations. Might be a very good
addition to my eLua project using the LLVM ARM backend.

On Wed, Aug 27, 2008 at 11:45 AM, Robert G. Jakabosky
<bobby@sharedrealm.com> wrote:
> I would like to announce the availability of llvm-lua.
>
> llvm-lua, converts Lua bytecode to LLVM IR code and supports JIT and static
> compiling.  Using LLVM gives Lua JIT support on cpu architectures other then
> x86.
>
> I converted the Lua bytecode dispatch loop code into a set of C functions one
> for each opcode.  The opcode functions take two parmeters one is the current
> Lua function's state, and the other is the 32bit opcode.  The function state
> holds all the local variables that where outside the dispatch loop
> (lua_State, stack base, constants, closure).  That set of opcode functions is
> compiled into a LLVM bitcode file (called lua_vm_ops.bc) that is used by
> llvm-lua at runtime.  llvm-lua load that bitcode file on start-up (right now
> it only looks in the working directory for 'lua_vm_ops.bc', I need to find a
> better way to load it).
>
> Each Lua function in converted one LLVM function with each Lua opcode in that
> function being converted into a function call to one of the opcode functions
> in lua_vm_ops.bc with the opcode's 32bit value being a constant for the
> second parmeter.  Most of those function calls are inlined before running a
> few LLVM optimization passes over the whole function.
>
> The performance is better then the normal lua vm on most scripts that I have
> tried.  For one script I had to disable JIT for any Lua function that had
> more then 800 opcodes since the LLVM codegen phase was taking atleast a
> second to codegen the LLVM IR to machine code.  The first time I ran the
> meteor.lua script it used more then 30 seconds to codegen all the Lua code,
> where as the normal Lua vm took less then 4 seconds to run the whole script.
> See the attached benchmark.log comparing the normal Lua vm with llvm-lua,
> native, and luajit.  The "native" column shows the scripts after they have
> been compiled to machine code and made into standalone executables, the time
> for that column doesn't include the compile time.  All the code used in this
> benchmark to compare the VMs can be downloaded from the project's website.
>
> The code can be downloaded from the project's website:
> http://code.google.com/p/llvm-lua/
>
> --
> Robert G. Jakabosky
>