Re: JIT test crash

[Michael Goffioul]

On Fri, Aug 3, 2012 at 7:13 PM, Max Brister <address@hidden> wrote:

On Fri, Aug 3, 2012 at 1:05 PM, Michael Goffioul

<address@hidden> wrote:
> On Thu, Aug 2, 2012 at 8:54 PM, Michael Goffioul
> <address@hidden> wrote:
>>
>> On Thu, Aug 2, 2012 at 6:42 PM, Max Brister <address@hidden> wrote:
>>>
>>> On Thu, Aug 2, 2012 at 8:36 AM, Michael Goffioul
>>> <address@hidden> wrote:
>>> > On Thu, Aug 2, 2012 at 1:57 PM, Max Brister <address@hidden> wrote:
>>> >>[snip]
>>>
>>> >>
>>> >> The output with OCTAVE_JIT_DEBUG looks correct to me.
>>> >>
>>> >> I have attached the patch for llvm 3.1.
>>> >
>>> >
>>> > I applied it, but it didn't change anything (the generated assembly
>>> > looks
>>> > exactly the same). If I'm reading this [1] correctly (XF86SubTarget
>>> > constructor), the stack alignment was already set to 4 anyway. And in
>>> > [2],
>>> > in X86_32TargetMachine constructor, the native stack alignment is also
>>> > specified on 4 bytes (trailing "-S32" at line 45).
>>> >
>>> > Michael.
>>> >
>>> > [1]
>>> >
>>> > https://github.com/earl/llvm-mirror/blob/master/lib/Target/X86/X86Subtarget.cpp
>>> > [2]
>>> >
>>> > https://github.com/earl/llvm-mirror/blob/master/lib/Target/X86/X86TargetMachine.cpp
>>>
>>> Actually, that makes sense. In order to use the sse instruction, we
>>> really want the stack to 16 byte aligned I think. Can you try changing
>>> the stack alignment to 16 bytes instead of 4?
>>
>>
>> No luck. I've modified your patch to read:
>>
>> opts.StackAlignmentOverride = 16
>>
>> For your information, I've attached the generated assembly for the 4-bytes
>> and 16-bytes case. The code still crashes, but at an earlier location. Now
>> it crashes at the MOVAPD call (address 02D300BC). If you compare with the
>> 4-bytes case, the latter uses MOVUPD instead, so it doesn't crash. Also if
>> you compare the 2 files, you see that in the 16-bytes case, all stack
>> offsets are multiple of 16 bytes, but I don't see any code to realign the
>> stack on a 16-bytes boundary.
>>
>> The bottom line is: within the generated code, the stack is kept aligned
>> on 16-bytes, but as there's no forced realignment, it entirely depends on
>> the stack alignment on function entry.
>
>
> Any update, ideas or suggestions?
>
> Michael.
>

Michael,

This defiantly looks like a bug in LLVM to me. I'll bring it up with
the LLVM people. In the mean time I'm thinking of not using the SSE
instructions for complex operations. I'm not sure how much benefit
there is considering complex numbers only have two values.

In the mean time I think it might be useful if I could test JIT on
msvc directly. Are you build scripts available somewhere?

I've put my build script (and current octave patch) available at these locations:

http://dl.dropbox.com/u/45539519/octave-build2.zip

http://dl.dropbox.com/u/45539519/msvc_compile_fix

The entry point is the build.sh script, that I call like:

./build.sh --msvc --prefix=/c/Software/VC10Libs <module_name>

where <module_name> is the name of the module to compile (see modules/ subdir for a module list). Note, this is a DIY framework, don't expect too much from it.

Michael.