[llvm] r194373 - [NVPTX] Blacklist TailDuplicate pass

[Justin Holewinski]

The problem is here (TailDuplication.cpp):

236├>      MachineInstr *DefMI = MRI->getVRegDef(VReg);

MachineRegisterInfo::getVRegDef assumes SSA form (and assertions if its
not), but MRI->isSSA() is false at this time.

I plan on filing a bug for this, but I don't have the time to look into
this pass at the moment.


On Mon, Nov 11, 2013 at 9:50 AM, Tom Stellard <tom at stellard.net> wrote:

> On Mon, Nov 11, 2013 at 12:58:14PM -0000, Justin Holewinski wrote:
> > Author: jholewinski
> > Date: Mon Nov 11 06:58:14 2013
> > New Revision: 194373
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=194373&view=rev
> > Log:
> > [NVPTX] Blacklist TailDuplicate pass
> >
> > This causes issues with virtual registers.  We will likely need
> > to fix TailDuplicate in the future, or introduce a new version
> > that plays nicely with vregs.
> >
>
> Do you have a testcase to demonstrate what TailDuplicate was doing
> wrong?  It would be great if you could file a bug for this.
>
> -Tom
>
> > Modified:
> >     llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp
> >
> > Modified: llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp?rev=194373&r1=194372&r2=194373&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp (original)
> > +++ llvm/trunk/lib/Target/NVPTX/NVPTXTargetMachine.cpp Mon Nov 11
> 06:58:14 2013
> > @@ -126,6 +126,7 @@ void NVPTXPassConfig::addIRPasses() {
> >    disablePass(&PrologEpilogCodeInserterID);
> >    disablePass(&MachineCopyPropagationID);
> >    disablePass(&BranchFolderPassID);
> > +  disablePass(&TailDuplicateID);
> >
> >    TargetPassConfig::addIRPasses();
> >    addPass(createGenericToNVVMPass());
> >
> >
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-- 

Thanks,

Justin Holewinski
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