llvm dev - Jul 2010 - [LLVMdev] simple way to print disassembly of final code from jit?

Thanks Reid - I'm on Windows. I guess I just assumed I was missing
something obvious in how to hook up the JIT and disassembler! Given
the nice looking disassembly code I found, I thought people would be
doing it all the time :-)

b.



On Tue, Jul 6, 2010 at 8:41 PM, Reid Kleckner <reid.kleckner at gmail.com>
wrote:
> If you're on a recent flavor of Linux, you may be able to just go into
> gdb and type "disas <pointer-to-JITed-code>".  More detail
here:
> http://llvm.org/docs/DebuggingJITedCode.html
>
> If you still want to do it programmatically, I think you might be
> stuck.  IIRC the length known by the JIT memory allocator is an
> overestimate (it's rounded up for alignment), so the disassembler will
> hit garbage at the end.
>
> Reid
>
> On Tue, Jul 6, 2010 at 3:07 PM, Bill O'Hara <billtohara at
gmail.com> wrote:
>> Hi,
>>
>> With the new llvm-mc code for disassembling, what is the recommended
>> way to disassemble the final code produced by a JIT compiler backend?
>> (Eg. in the toy.cpp example from the tutorial).
>>
>> I can get the void* for the final code, but I don't know its length
-
>> superficially at least it appears I need to know the length to
>> disassemble it as a buffer?
>>
>> Thanks
>> b.
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>

If you can manage windbg, you can use "uF (address|symbol)" to dump
out a decent function scoped disassembly. Docs are here:
http://msdn.microsoft.com/en-us/library/ff558942(VS.85).aspx

-n 

-----Original Message-----
From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Bill O'Hara
Sent: Tuesday, July 06, 2010 9:40 PM
To: Reid Kleckner
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] simple way to print disassembly of final code from jit?

Thanks Reid - I'm on Windows. I guess I just assumed I was missing
something obvious in how to hook up the JIT and disassembler! Given
the nice looking disassembly code I found, I thought people would be
doing it all the time :-)

b.



On Tue, Jul 6, 2010 at 8:41 PM, Reid Kleckner <reid.kleckner at gmail.com>
wrote:
> If you're on a recent flavor of Linux, you may be able to just go into
> gdb and type "disas <pointer-to-JITed-code>".  More detail
here:
> http://llvm.org/docs/DebuggingJITedCode.html
>
> If you still want to do it programmatically, I think you might be
> stuck.  IIRC the length known by the JIT memory allocator is an
> overestimate (it's rounded up for alignment), so the disassembler will
> hit garbage at the end.
>
> Reid
>
> On Tue, Jul 6, 2010 at 3:07 PM, Bill O'Hara <billtohara at
gmail.com> wrote:
>> Hi,
>>
>> With the new llvm-mc code for disassembling, what is the recommended
>> way to disassemble the final code produced by a JIT compiler backend?
>> (Eg. in the toy.cpp example from the tutorial).
>>
>> I can get the void* for the final code, but I don't know its length
-
>> superficially at least it appears I need to know the length to
>> disassemble it as a buffer?
>>
>> Thanks
>> b.
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>
_______________________________________________
LLVM Developers mailing list
LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Bill,

I'm coincidently planning right now on doing exactly the same things as you.
I haven't yet had a chance to implement the code, but I can point you to how
I currently believe you can get access to what you need. If you take a look at
the code for the implementation of lvm::JIT::runJITOnFunction(Function *,
MachineCodeInfo *), you'll see that if a MachineCodeInfo parameter is
supplied, it is populated via a call to setAddress and setSize via the
registration of a JITEventListener on the Jitting of the given function. I'm
almost certain this is the address and size that is needed by the disassembler.
You then should be able to either use runJITOnFunction as part of your current
JIT compilation process or do the same thing it does by way of registering your
own JITEventListener to get access to the required values.

O.J.

p.s. let me know if you are successful in getting this working, I hope you have
some success.

On 07/07/2010, at 2:10 PM, Bill O'Hara wrote:
> Thanks Reid - I'm on Windows. I guess I just assumed I was missing
> something obvious in how to hook up the JIT and disassembler! Given
> the nice looking disassembly code I found, I thought people would be
> doing it all the time :-)
> 
> b.
> 
> 
> 
> On Tue, Jul 6, 2010 at 8:41 PM, Reid Kleckner <reid.kleckner at
gmail.com> wrote:
>> If you're on a recent flavor of Linux, you may be able to just go
into
>> gdb and type "disas <pointer-to-JITed-code>".  More
detail here:
>> http://llvm.org/docs/DebuggingJITedCode.html
>> 
>> If you still want to do it programmatically, I think you might be
>> stuck.  IIRC the length known by the JIT memory allocator is an
>> overestimate (it's rounded up for alignment), so the disassembler
will
>> hit garbage at the end.
>> 
>> Reid
>> 
>> On Tue, Jul 6, 2010 at 3:07 PM, Bill O'Hara <billtohara at
gmail.com> wrote:
>>> Hi,
>>> 
>>> With the new llvm-mc code for disassembling, what is the
recommended
>>> way to disassemble the final code produced by a JIT compiler
backend?
>>> (Eg. in the toy.cpp example from the tutorial).
>>> 
>>> I can get the void* for the final code, but I don't know its
length -
>>> superficially at least it appears I need to know the length to
>>> disassemble it as a buffer?
>>> 
>>> Thanks
>>> b.
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>> 
>> 
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Thanks for all the hints everyone.

Based on your suggestion, O.J., I've added code to toy.cpp from the
tutorial to disassemble.

ready> 1+1;
ready> 	movabsq	$140737353367568, %rax
	movsd	(%rax), %xmm0
	ret
Evaluated to 2.000000
ready>

Which looks correct by inspection - printing the byte array to stdout
and feeding it to llvm-mc offline produces the same code as one would
also expect.

echo '0x48 0xb8 0x10 0x40 0xf4 0xf7 0xff 0x7f 0x0 0x0 0xf2 0xf 0x10
0x0 0xc3' |llvm-mc -disassemble -triple=x86_64-PC-Linux
	movabsq	$140737353367568, %rax
	movsd	(%rax), %xmm0
	ret


b.


On Wed, Jul 7, 2010 at 3:07 AM,  <o.j.sivart at gmail.com>
wrote:
> Hi Bill,
>
> I'm coincidently planning right now on doing exactly the same things as
you. I haven't yet had a chance to implement the code, but I can point you
to how I currently believe you can get access to what you need. If you take a
look at the code for the implementation of lvm::JIT::runJITOnFunction(Function
*, MachineCodeInfo *), you'll see that if a MachineCodeInfo parameter is
supplied, it is populated via a call to setAddress and setSize via the
registration of a JITEventListener on the Jitting of the given function. I'm
almost certain this is the address and size that is needed by the disassembler.
You then should be able to either use runJITOnFunction as part of your current
JIT compilation process or do the same thing it does by way of registering your
own JITEventListener to get access to the required values.
>
> O.J.
>
> p.s. let me know if you are successful in getting this working, I hope you
have some success.
>
> On 07/07/2010, at 2:10 PM, Bill O'Hara wrote:
>
>> Thanks Reid - I'm on Windows. I guess I just assumed I was missing
>> something obvious in how to hook up the JIT and disassembler! Given
>> the nice looking disassembly code I found, I thought people would be
>> doing it all the time :-)
>>
>> b.
>>
>>
>>
>> On Tue, Jul 6, 2010 at 8:41 PM, Reid Kleckner <reid.kleckner at
gmail.com> wrote:
>>> If you're on a recent flavor of Linux, you may be able to just
go into
>>> gdb and type "disas <pointer-to-JITed-code>".  More
detail here:
>>> http://llvm.org/docs/DebuggingJITedCode.html
>>>
>>> If you still want to do it programmatically, I think you might be
>>> stuck.  IIRC the length known by the JIT memory allocator is an
>>> overestimate (it's rounded up for alignment), so the
disassembler will
>>> hit garbage at the end.
>>>
>>> Reid
>>>
>>> On Tue, Jul 6, 2010 at 3:07 PM, Bill O'Hara <billtohara at
gmail.com> wrote:
>>>> Hi,
>>>>
>>>> With the new llvm-mc code for disassembling, what is the
recommended
>>>> way to disassemble the final code produced by a JIT compiler
backend?
>>>> (Eg. in the toy.cpp example from the tutorial).
>>>>
>>>> I can get the void* for the final code, but I don't know
its length -
>>>> superficially at least it appears I need to know the length to
>>>> disassemble it as a buffer?
>>>>
>>>> Thanks
>>>> b.
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>
>>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>