Re: JIT test crash

[Michael Goffioul]

On Fri, Dec 28, 2012 at 4:04 PM, Max Brister <address@hidden> wrote:

On Wed, Dec 26, 2012 at 7:20 AM, Michael Goffioul
<address@hidden> wrote:
> On Wed, Dec 26, 2012 at 12:01 AM, Max Brister <address@hidden> wrote:
>>
>> Well, there was recently a new version of LLVM, it would be nice if
>> that just fixed the issue (I don't see anything relevant in the
>> release notes though).
>>
>> If that doesn't work, then we should try implementing complex numbers
>> as a llvm::ArrayType or llvm::StructureType internally in Octave.
>> Currently, complex numbers are implemented with an llvm::VectorType,
>> which LLVM emits vectorized assembly for. If I recall correctly, that
>> was causing MSVC to emit bad instructions. I can prepare a patch to do
>> this, if you want to try it.
>>
>> If that doesn't work, then we need to trace the execution of LLVM to
>> figure out why bad code is being generated.
>
>
> Note that IIRC, the problem was data alignment. GCC aligns by default on
> 16-bytes boundary, MSVC on 4-bytes. If LLVM assumes GCC alignment, then it
> can emit bad vectorized code.

Yes, hopefully avoiding the vectorized instructions will fix the
issue. I'm not sure how much of a speedup we get by vectorizing
operations on complex numbers anyways.

I have attached a patch that *should* avoid these vectorized instructions.

Thanks, Max. Unfortunately, the JIT code does not compile anymore with MSVC at the moment. My change

http://hg.savannah.gnu.org/hgweb/octave/rev/fd8d1a616be1

has been partially reverted by yours

http://hg.savannah.gnu.org/hgweb/octave/rev/3f43e9d6d86e

So I need to find a way to work around the issue, but it may be hard to find. The actual problem is that <Cell.h> got included when compiling Array-jit.cc (pulled from pt-jit.h -> symtab.h -> oct-obj.h -> Cell.h). The class Cell is marked with dllexport and inherits from Array<octave_value>. This makes MSVC to instantiate all Array<octave_value> methods. However, as Array-jit.cc also includes <Array.cc>, it makes MSVC to try to instantiate code that is not valid when T = octave_value.

Michael.