[Sparc] Load address with SETHI

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1

Some more information on what I have so far. I’ll actually focus on the longjmp side, as the problem is probably easier.

I need to get the SETHI / OR combination inserted where the comment
“*** Need to use the SETHI / OR combination here. ***” appears in the
code below, but I’m not sure that this is done anywhere near this piece
of code, so I’ll include all the relevant parts that I can find of my
current implementation.

I don’t understand what exactly you want to materialize here. Shouldn’t
the address of the buffer already be an operand at this point?

Joerg

Quite possibly, I’ve over-simplified my example. Perhaps I should have focussed more on the setjmp part, which is actually where I was coding anyway. In this, I need to store the address of the instruction after I’ve lowered the intrinsic into a buffer so that I can recover this and jump back to it from the longjmp intrinsic.

There are two or three parts, and I’m not sure how to go about either. After I get these working, the rest is (I think) plain-sailing:

(1) I need to take the address of the instruction after the lowered setjmp intrinsic, which I think requires that I create a new basic block

(2) I need to get the address of this basic block, at lowering time, and get it into a register using the SETHI / OR combination (I presume). Once it’s in the register, I can store it in the buffer easily. There must surely be a good way to load an address using SETHI / OR, but nothing I’ve tried (including “makeAddress”) works so far. I guess I could code each of SETHI and OR individually, but surely there’s some code around to take care of this already.

(3) Is there anything else? Do I need any indicators to let the back-end know it’ll need to fix-up the address taken in step (2) later in the compilation - or possibly in the link - pipeline?

2

Hi,

Can anyone help me to fill in the missing details here please? I’m sure this is a very short piece of code, but I can’t find the right way of doing this…

MachineBasicBlock* SparcTargetLowering::
emitEHSjLjLongJmp(MachineInstr *MI,
MachineBasicBlock *MBB) const
{
[… Code omitted for brevity]

MVT PVT = getPointerTy(MF->getDataLayout());
unsigned PtrSize = PVT.getStoreSize();
// We’ll deal with 64 bit implementations when the 32 bit version is working!
assert(PVT == MVT::i32 && “Invalid Pointer Size!”);

MachineBasicBlock *jumpToMBB = MF->CreateMachineBasicBlock(BB);
MF->insert(I, mainMBB);

const TargetRegisterClass *PtrRC = getRegClassFor(PVT);
unsigned LabelReg = MRI.createVirtualRegister(PtrRC);

// Need to load the address of “jumpToMBB” into register “LabelReg”, so that
// we can then (later) store this in a buffer, to be recovered by “longjmp” as
// the location to resume execution at (via a JMPL instruction).

// We need something like this, garnered from the PPC implementation.
// What is the equivalent code in Sparc utilizing the instructions SETHI and OR?
MIB = BuildMI(mainMBB, DL,
TII->get(Subtarget.isPPC64() ? PPC::MFLR8 : PPC::MFLR), LabelReg);

// …or possibly, it should be something like this, using addMBB (I know this isn’t legal, BTW)
MIB = BuildMI(mainMBB, DL,
TII->get(SP::LDri, LabelReg).addMBB(jumpToMBB);

[… Code omitted for brevity]
}