[Mono-dev] Question(s) about the JIT implementation

[Zoltan Varga]

Hi,

 * I think the compare opcodes can be rewritten in the lowering pass.
* You can disable IMT first by simply not declaring MONO_ARCH_IMT_REG. The same
   goes for MONO_ARCH_VTABLE_REG.
* Instead of trying to run hello.exe, you should try running the JIT
regression tests, which
  consists of many small functions so it is much easier to track down
failures. They can
  be compiled in another machine by type-ing make check in the mini
directory, then
  copied to the MIPS machine, then run there by type-ing make check.

                         Zoltan

On Wed, Nov 26, 2008 at 7:14 PM, Mark Mason <mmason at upwardaccess.com> wrote:
> Hello all,
>
> I'm working on getting the MIPS JIT ported back up to the top-of-tree,
> and have run into a few issues - primarily with areas that have changed
> a lot since I looked at it last. I am hoping that someone can spare a
> couple of sentences to point me in the right direction here.
>
> As it stands now, hello.exe on MIPS gets as far as the following:
>
> mason at 10:~/Mono-MIPS/mono/mono/mini$ ./mono hello.exe
> Stacktrace:
>
>  at System.Globalization.TextInfo..ctor
> (System.Globalization.CultureInfo,int,void*,bool) <0xffffffff>
>  at System.Globalization.TextInfo..ctor
> (System.Globalization.CultureInfo,int,void*,bool) <0x00148>
>  at System.Globalization.CultureInfo.ConstructInvariant (bool)
> <0x001c0>
>  at System.Globalization.CultureInfo..ctor (int,bool,bool) <0x00088>
>  at System.Threading.Thread.get_CurrentCulture () <0xffffffff>
>  at System.Threading.Thread.get_CurrentCulture () <0x0011c>
>  at System.NumberFormatter..ctor (System.Threading.Thread) <0x00078>
>  at System.Threading.Thread.AcquireNumberFormatter () <0x0006c>
>  at System.NumberFormatter.GetInstance () <0x00030>
>  at System.NumberFormatter.NumberToString
> (string,int,System.IFormatProvider) <0x00024>
>  at System.NumberFormatter.NumberToString (int,System.IFormatProvider)
> <0x0007c>
>  at int.ToString () <0x0002c>
>  at System.Text.Encoding.GetEncoding (int) <0x003cc>
>  at System.Text.Encoding.get_Default () <0x00210>
>  at System.Console..cctor () <0x00210>
>  at (wrapper runtime-invoke) object.runtime_invoke_void
> (object,intptr,intptr,intptr) <0xffffffff>
>  at TestBed1.MainClass.Main (string[]) <0xffffffff>
>  at TestBed1.MainClass.Main (string[]) <0x0002c>
>  at (wrapper runtime-invoke)
> TestBed1.MainClass.runtime_invoke_void_object
> (object,intptr,intptr,intptr) <0xffffffff>
> Aborted
>
> Rewriting: As MIPS uses compare-and-branch opcodes rather than separate
> compare/branch opcodes (there's no condition register for one thing),
> what we used to do was rewrites to MIPS specific opcodes in the burg
> rules. Burg isn't with us any more, but the rewriting still needs to
> happen. I'm currently doing it in peephole pass 1, but this really needs
> to move into a separate pass which isn't an "optimization" that can be
> disabled from the command line. Maybe add mono_arch_rewrite_pass_1() and
> the appropriate enabling macro, and call it right after the lowering
> pass? Thoughts?
>
>
> IMT: I'm not quite clear on what this is, which makes adding support for
> it a bit difficult. I have it enabled at the moment, and hello world is
> crashing on the first "use" of it (see below). I know that I'm locating
> the LMF correctly [because MIPS LMFs have magic numbers ;)] but I'm no
> where near so confident about MONO_ARCH_IMT_REG,
> mono_arch_build_imt_thunk (which hasn't been called yet below), and
> other friends.
>
> (gdb) r hello.exe
> Starting program: /home/mason/Mono-MIPS/mono/mono/mini/mono hello.exe
> [Thread debugging using libthread_db enabled]
> [New Thread 16384 (LWP 14569)]
> [New Thread 32769 (LWP 14572)]
> [New Thread 16386 (LWP 14573)]
> [New Thread 32771 (LWP 14574)]
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 16384 (LWP 14569)]
> 0x00548ce4 in mono_convert_imt_slot_to_vtable_slot (slot=0x8395c0,
> regs=0x7f88b440, code=0x2b3ffeb0 "\024@", method=0x84b3f8,
> impl_method=0x0)
>    at mini-trampolines.c:63
> 63                      interface_offset = mono_class_interface_offset
> (vt->klass, imt_method->klass);
> (gdb) where
> #0  0x00548ce4 in mono_convert_imt_slot_to_vtable_slot (slot=0x8395c0,
> regs=0x7f88b440, code=0x2b3ffeb0 "\024@", method=0x84b3f8,
>    impl_method=0x0) at mini-trampolines.c:63
> #1  0x0054a0f0 in mono_magic_trampoline (regs=0x7f88b440,
> code=0x2b3ffeb0 "\024@", m=0x84b3f8, tramp=0x0) at
> mini-trampolines.c:335
> #2  0x2aac8164 in ?? ()
>
>
> Thanks all,
> Mark
>
>
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