[clang] [llvm] [SystemZ] Add support for __builtin_setjmp and __builtin_longjmp (PR #116642)

[Ulrich Weigand via cfe-commits]

================
@@ -940,7 +947,242 @@ bool SystemZTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT,
   return SystemZVectorConstantInfo(Imm).isVectorConstantLegal(Subtarget);
 }
 
-/// Returns true if stack probing through inline assembly is requested.
+
+MachineBasicBlock *
+SystemZTargetLowering::emitEHSjLjSetJmp(MachineInstr &MI,
+                                     MachineBasicBlock *MBB) const {
+
+  DebugLoc DL = MI.getDebugLoc();
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
+  const SystemZRegisterInfo *TRI = Subtarget.getRegisterInfo();
+
+  MachineFunction *MF = MBB->getParent();
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+
+  const BasicBlock *BB = MBB->getBasicBlock();
+  MachineFunction::iterator I = ++MBB->getIterator();
+
+  Register DstReg = MI.getOperand(0).getReg();
+  const TargetRegisterClass *RC = MRI.getRegClass(DstReg);
+  assert(TRI->isTypeLegalForClass(*RC, MVT::i32) && "Invalid destination!");
+  Register mainDstReg = MRI.createVirtualRegister(RC);
+  Register restoreDstReg = MRI.createVirtualRegister(RC);
+
+  MVT PVT = getPointerTy(MF->getDataLayout());
+  assert((PVT == MVT::i64 || PVT == MVT::i32) &&
+         "Invalid Pointer Size!");
+  // For v = setjmp(buf), we generate.
+  // Algorithm:
+  //
+  //                 ---------
+  //                | thisMBB |
+  //                 ---------
+  //                     |
+  //         ------------------------
+  //        |                        |
+  //     ----------           ---------------
+  //    |  mainMBB |         | restoreMBB    |
+  //    |   v = 0  |         |  v = 1        |
+  //     ----------           ---------------
+  //        |                        |
+  //         -------------------------
+  //                     |
+  //           -----------------------------
+  //          |       sinkMBB               |
+  //          | phi(v_mainMBB,v_restoreMBB) |
+  //           -----------------------------
+  // thisMBB:
+  //  buf[0] = Frame Pointer if hasFP.
+  //  buf[LabelOffset] = restoreMBB <-- takes address of restoreMBB.
+  //  buf[BCOffset] = Backchain value if building with -mbackchain.
+  //  buf[SPOffset] = Stack Pointer.
+  //  buf[LPOffset] = We never write this slot with  R13, gcc stores R13 always.
+  //  SjLjSetup restoreMBB
+  // mainMBB:
+  //  v_main = 0
+  // sinkMBB:
+  //  v = phi(v_main, v_restore)
+  // restoreMBB:
+  //  v_restore = 1
+
+  MachineBasicBlock *thisMBB = MBB;
+  MachineBasicBlock *mainMBB = MF->CreateMachineBasicBlock(BB);
+  MachineBasicBlock *sinkMBB = MF->CreateMachineBasicBlock(BB);
+  MachineBasicBlock *restoreMBB = MF->CreateMachineBasicBlock(BB);
+
+  MF->insert(I, mainMBB);
+  MF->insert(I, sinkMBB);
+  MF->push_back(restoreMBB);
+  restoreMBB->setMachineBlockAddressTaken();
+
+  MachineInstrBuilder MIB;
+
+  // Transfer the remainder of BB and its successor edges to sinkMBB.
+  sinkMBB->splice(sinkMBB->begin(), MBB,
+                  std::next(MachineBasicBlock::iterator(MI)), MBB->end());
+  sinkMBB->transferSuccessorsAndUpdatePHIs(MBB);
+  
+
+  // thisMBB:
+  const int64_t LabelOffset = 1 * PVT.getStoreSize(); // Slot 2.
+  const int64_t SPOffset = 3 * PVT.getStoreSize(); // Slot 4.
+
+  // Buf address.
+  Register BufReg = MI.getOperand(1).getReg();
+
+  unsigned LabelReg = 0;
+  const TargetRegisterClass *PtrRC = getRegClassFor(PVT);
+  LabelReg = MRI.createVirtualRegister(PtrRC); 
+
+  // prepare IP for longjmp.
+  BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::LARL), LabelReg)
+          .addMBB(restoreMBB);
+
+  // store IP for return from jmp, slot 2, offset = 1.
+  BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::STG))
+          .addReg(LabelReg)
+          .addReg(BufReg)
+          .addImm(LabelOffset)
+          .addReg(0);
+
+  bool HasFP =  Subtarget.getFrameLowering()->hasFP(*MF);
+  if (HasFP) {
+     const int64_t FPOffset = 0; 
+     BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::STG))
+          .addReg(SystemZ::R11D)
----------------
uweigand wrote:

Even though this function will probably only be used on Linux, we still should use `getFramePointerRegister()` (from `Subtarget.getSpecialRegisters()`) here instead of hardcoding R11.  

https://github.com/llvm/llvm-project/pull/116642