[LLVMdev] Broken PLT on ARM from R183966

[JF Bastien]

I'm not very familiar with relocations but your fix looks the same
as ARMTargetLowering::LowerCall, so from that perspective it lgtm (but I
may be missing something).


On Wed, Aug 21, 2013 at 8:04 AM, Logan Chien <tzuhsiang.chien at gmail.com>wrote:

> Hi Anton and JF,
>
>   Thanks for your review.  After reading the source code more carefully, I
> have come up with a different way fix this issue.  We can simply resolve
> this issue by adding ARMII::MO_PLT flags with MachineInstrBuilder in
> FastISel pass (without failing back to DAG lowering).
>
>   The new patch is attached, and the test case is not changed.  Sorry for
> your inconvenience.  Please have a look.  Thanks for your help.
>
> Sincerely,
> Logan
>
>
> On Wed, Aug 21, 2013 at 10:52 PM, JF Bastien <jfb at google.com> wrote:
>
>> lgtm
>>
>>
>> On Wed, Aug 21, 2013 at 3:18 AM, Anton Korobeynikov <
>> anton at korobeynikov.info> wrote:
>>
>>> LGTM
>>>
>>> On Wed, Aug 21, 2013 at 1:51 PM, Logan Chien <tzuhsiang.chien at gmail.com>
>>> wrote:
>>> > Hi,
>>> >
>>> >   I have created a workaround to deal with the PIC function call.
>>>  With this
>>> > patch, the FastISel will switch back to DAG lowering mechanism if (1)
>>> there
>>> > is a function call in the basic block and (2) the relocation model is
>>> PIC.
>>> > Please have a look.  Hoping the patch will help.
>>> >
>>> > Sincerely,
>>> > Logan
>>> >
>>> >
>>> > On Wed, Aug 21, 2013 at 10:17 AM, Gordon Keiser <gkeiser at arxan.com>
>>> wrote:
>>> >>
>>> >> Cool, I'll file a bug tomorrow at work and add you to the CC list.
>>> >>
>>> >> Thanks!
>>> >> Gordon Keiser
>>> >> Software Development Engineer
>>> >> Arxan Technologies
>>> >> gkeiser at arxan.com  www.arxan.com
>>> >> Protecting the App EconomyT
>>> >>
>>> >> > -----Original Message-----
>>> >> > From: Eric Christopher [mailto:echristo at gmail.com]
>>> >> > Sent: Tuesday, August 20, 2013 9:47 PM
>>> >> > To: Gordon Keiser
>>> >> > Cc: llvmdev at cs.uiuc.edu; JF Bastien
>>> >> > Subject: Re: [LLVMdev] Broken PLT on ARM from R183966
>>> >> >
>>> >> > Filing a bug would be a good start, go ahead and cc me and
>>> >> > jfb at google.com.
>>> >> >
>>> >> > Thanks!
>>> >> >
>>> >> > -eric
>>> >> >
>>> >> > On Tue, Aug 20, 2013 at 6:10 PM, Gordon Keiser <gkeiser at arxan.com>
>>> >> > wrote:
>>> >> > > For ARM targets on linux, revision 183966 made Fast ISel default.
>>> >> > > Unfortunately, Fast ISel is broken in terms of applying the
>>> >> > > ARMII::MO_PLT flags to calls in PIC mode (at least when emitting
>>> >> > > assembly);  it never does this.  The normal ISel pass handles this
>>> >> > > situation correctly so a temporary local change to disable
>>> FastISel
>>> >> > > for linux / NaCl targets is working for me right now.
>>> >> > >
>>> >> > >
>>> >> > >
>>> >> > > I'm not very familiar with the ISel passes.  I'm guessing the
>>> correct
>>> >> > > thing to do here would be to apply the attribute correctly in
>>> FastISel
>>> >> > > so it works, but I'm kind of unfamiliar with this part of the
>>> code and
>>> >> > > won't have time to dig into it right now, although I'm willing to
>>> do
>>> >> > > it if someone points me to the right area of code.
>>> >> > >
>>> >> > >
>>> >> > >
>>> >> > > In the meantime, would it be worthwhile to submit in a
>>> modification to
>>> >> > > disable FastISel for non-darwin targets, or is it likely to be
>>> fixed
>>> >> > > quickly?
>>> >> > >
>>> >> > >
>>> >> > >
>>> >> > > -Gordon
>>> >> > >
>>> >> > >
>>> >> > > _______________________________________________
>>> >> > > LLVM Developers mailing list
>>> >> > > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> >> > > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>> >> > >
>>> >>
>>> >> _______________________________________________
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>>> >> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>> >
>>> >
>>> >
>>> > _______________________________________________
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>>> >
>>>
>>>
>>>
>>> --
>>> With best regards, Anton Korobeynikov
>>> Faculty of Mathematics and Mechanics, Saint Petersburg State University
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>
>>
>>
>
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