[LLVMdev] Inserting a branch in PPCTargetLowering::LowerFormalArguments_SVR4

[Hal Finkel]

Jim,

Thanks! Might it be possible to do this another way? For example, could
I insert some special pseudo-instructions and then turn them into
branches later on?

 -Hal

On Thu, 10 May 2012 11:39:10 -0700
Jim Grosbach <grosbach at apple.com> wrote:

> Hi Hal,
> 
> For lowering code that requires inserting branches, you need to use a
> custom inserter, yes. Theoretically, that does indeed sound like what
> you want to do here.
> 
> It's complicated by the general structure of argument passing,
> though. In particular, there's lots of assumptions about the call
> sequence stuff. I don't know if things are smart enough (EH in
> particular worries me) to handle this sort of thing. On the plus
> side, there are copious assert() bits in there to catch it if the
> compiler gets itself confused, so you should know sooner rather than
> later if something goes wonky.
> 
> -Jim
> 
> On May 10, 2012, at 11:25 AM, Hal Finkel <hfinkel at anl.gov> wrote:
> 
> > I hate to be bothersome, but can someone please comment on this?
> > 
> > Thanks again,
> > Hal
> > 
> > On Thu, 3 May 2012 14:49:04 -0500
> > Hal Finkel <hfinkel at anl.gov> wrote:
> > 
> >> Hello,
> >> 
> >> The current code in PPCTargetLowering::LowerFormalArguments_SVR4
> >> contains a FIXME over the code which saves the live floating-point
> >> registers to the stack. The FIXME states that this should only be
> >> done if CR bit 6 is set. I've been told that the lack of this
> >> check is preventing clang/LLVM from compiling a functional FreeBSD
> >> kernel on PPC.
> >> 
> >> Is is possible to insert another branch in LowerFormalArguments?
> >> Some of the atomic instructions insert branches, but those are
> >> handled in EmitInstrWithCustomInserter. Can branches be inserted
> >> inside LowerFormalArguments in the same way?
> >> 
> >> Thanks in advance,
> >> Hal
> >> 
> > 
> > 
> > 
> > -- 
> > Hal Finkel
> > Postdoctoral Appointee
> > Leadership Computing Facility
> > Argonne National Laboratory
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 



-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory