[llvm-dev] need help for customized backend LowerFormalArguments

[Xiangyang Guo via llvm-dev]

Hi, Tim,

Thanks for your reply. You are right, my MOVE and copyPhysReg are wrong.
After I fix that, it works.

Regards,

Xiangyang

2015-11-25 17:27 GMT-05:00 Tim Northover <t.p.northover at gmail.com>:

> On 25 November 2015 at 14:06, Xiangyang Guo via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> >       const unsigned VReg =
> RegInfo.createVirtualRegister(&FOO::PRegsRegClass);
> >       RegInfo.addLiveIn(VA.getLocReg(), VReg);
> >       SDValue ArgIn = DAG.getCopyFromReg(Chain, dl, VReg, RegVT);
>
> Using MachineFunction::addLiveIn would probably be simpler, but I
> *think* this ought to be OK too.
>
> > However, when I use llc and print-after-all to check the machine
> > instructions. At very beginning, the machine instructions look like this:
> >
> >     %vreg1<def> = COPY %P1; PRegs:%vreg1
> >     %vreg0<def> = COPY %P0; PRegs:%vreg0
> >     %vreg3<def> = COPY %vreg0; GRRegsAdditional:%vreg3 PRegs:%vreg0
> >     %vreg4<def> = COPY %vreg1; GRRegsAdditional:%vreg4 PRegs:%vreg1
> >     %vreg2<def> = ADDINT %vreg3, %vreg4;
> GRRegsAdditional:%vreg2,%vreg3,%vreg4
> >     %R10<def> = COPY %vreg2; GRRegsAdditional:%vreg2 RET %R10
>
> This looks fine to me.
>
> > And after "Post-RA pseudo instruction expansion pass", it looks like this
>
> I don't suppose your copyPhysReg implementation does something
> degenerate for these? That's the callback that'll be used to actually
> implement any COPY pseudo-instructions that need to be materialised,
> not any TableGen related patterns you might have (as a general
> guideline, if you're writing a pattern for a MOV instruction, you're
> probably doing something wrong).
>
> It's a good idea for copyPhysReg to assert for anything it can't
> handle corrrectly.
>
> If it's not that, the entire output of "llc -debug" would be useful.
> Obviously a lot goes on between the two dumps you pasted here. Maybe
> some other pass is doing something slightly wrong.
>
> Cheers.
>
> Tim.
>
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