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

Implementation for __builtin_setjmp and __builtin_longjmp for SystemZ.

Author: anoopkg6

clang/lib/Basic/Targets/SystemZ.h

@@ -247,6 +247,8 @@ class LLVM_LIBRARY_VISIBILITY SystemZTargetInfo : public TargetInfo {
     return RegNo < 4 ? 6 + RegNo : -1;
   }
 
+  bool hasSjLjLowering() const override { return true; }
+
   std::pair<unsigned, unsigned> hardwareInterferenceSizes() const override {
     return std::make_pair(256, 256);
   }

clang/lib/CodeGen/CGBuiltin.cpp

@@ -4860,6 +4860,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     // Buffer is a void**.
     Address Buf = EmitPointerWithAlignment(E->getArg(0));
 
+    if (getTarget().getTriple().getArch() == llvm::Triple::systemz) {
+      // On this target, the back end fills in the context buffer completely.
+      // It doesn't really matter if the frontend stores to the buffer before
+      // calling setjmp, the back-end is going to overwrite them anyway.
+      Function *F = CGM.getIntrinsic(Intrinsic::eh_sjlj_setjmp);
+      return RValue::get(Builder.CreateCall(F, Buf.emitRawPointer(*this)));
+    }
+
     // Store the frame pointer to the setjmp buffer.
     Value *FrameAddr = Builder.CreateCall(
         CGM.getIntrinsic(Intrinsic::frameaddress, AllocaInt8PtrTy),

clang/test/CodeGen/SystemZ/builtin-setjmp-logjmp.c

@@ -0,0 +1,25 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
+// RUN: %clang --target=s390x-linux -S -emit-llvm -o - %s | FileCheck %s
+
+void *buf[20];
+// CHECK-LABEL: define dso_local void @foo(
+// CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[TMP0:%.*]] = call i32 @llvm.eh.sjlj.setjmp(ptr @buf)
+// CHECK-NEXT:    ret void
+//
+void foo()
+{
+  __builtin_setjmp (buf);
+}
+
+// CHECK-LABEL: define dso_local void @foo1(
+// CHECK-SAME: ) #[[ATTR0]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    call void @llvm.eh.sjlj.longjmp(ptr @buf)
+// CHECK-NEXT:    unreachable
+//
+void foo1()
+{
+  __builtin_longjmp (buf, 1);
+}

llvm/docs/ExceptionHandling.rst

@@ -374,10 +374,11 @@ overall functioning of this intrinsic is compatible with the GCC
 to interoperate.
 
 The single parameter is a pointer to a five word buffer in which the calling
-context is saved. The front end places the frame pointer in the first word, and
-the target implementation of this intrinsic should place the destination address
-for a `llvm.eh.sjlj.longjmp`_ in the second word. The following three words are
-available for use in a target-specific manner.
+context is saved. The format and contents of the buffer are target-specific.
+On certain targets (ARM, PowerPC, VE, X86), the front end places the 
+frame pointer in the first word and the stack pointer in the third word, 
+while the target implementation of this intrinsic fills in the remaining 
+words.  On other targets (SystemZ), saving the calling context to the buffer is left completely to the target implementation. 
 
 .. _llvm.eh.sjlj.longjmp:
 

llvm/lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -705,6 +705,11 @@ void SystemZAsmPrinter::emitInstruction(const MachineInstr *MI) {
     return;
   }
 
+  // EH_SjLj_Setup is a dummy terminator instruction of size 0.
+  // It is used to handle the clobber register for builtin setjmp.
+  case SystemZ::EH_SjLj_Setup:
+    return;
+
   default:
     Lower.lower(MI, LoweredMI);
     break;

llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

@@ -751,6 +751,11 @@ SystemZTargetLowering::SystemZTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::INTRINSIC_W_CHAIN, MVT::Other, Custom);
   setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
 
+  // We're not using SJLJ for exception handling, but they're implemented
+  // solely to support use of __builtin_setjmp / __builtin_longjmp.
+  setOperationAction(ISD::EH_SJLJ_SETJMP, MVT::i32, Custom);
+  setOperationAction(ISD::EH_SJLJ_LONGJMP, MVT::Other, Custom);
+
   // We want to use MVC in preference to even a single load/store pair.
   MaxStoresPerMemcpy = Subtarget.hasVector() ? 2 : 0;
   MaxStoresPerMemcpyOptSize = 0;
@@ -940,6 +945,240 @@ bool SystemZTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT,
   return SystemZVectorConstantInfo(Imm).isVectorConstantLegal(Subtarget);
 }
 
+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[FPOffset] = 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 FPOffset = 0;                         // Slot 1.
+  const int64_t LabelOffset = 1 * PVT.getStoreSize(); // Slot 2.
+  const int64_t BCOffset = 2 * PVT.getStoreSize();    // Slot 3.
+  const int64_t SPOffset = 3 * PVT.getStoreSize();    // Slot 4.
+
+  // Buf address.
+  Register BufReg = MI.getOperand(1).getReg();
+
+  const TargetRegisterClass *PtrRC = getRegClassFor(PVT);
+  unsigned 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);
+
+  auto *SpecialRegs = Subtarget.getSpecialRegisters();
+  bool HasFP = Subtarget.getFrameLowering()->hasFP(*MF);
+  if (HasFP) {
+    BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::STG))
+        .addReg(SpecialRegs->getFramePointerRegister())
+        .addReg(BufReg)
+        .addImm(FPOffset)
+        .addReg(0);
+  }
+
+  // Store SP.
+  BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::STG))
+      .addReg(SpecialRegs->getStackPointerRegister())
+      .addReg(BufReg)
+      .addImm(SPOffset)
+      .addReg(0);
+
+  // Slot 3(Offset = 2) Backchain value (if building with -mbackchain).
+  bool BackChain = MF->getSubtarget<SystemZSubtarget>().hasBackChain();
+  if (BackChain) {
+    Register BCReg = MRI.createVirtualRegister(RC);
+    auto *TFL = Subtarget.getFrameLowering<SystemZFrameLowering>();
+    MIB = BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::LG), BCReg)
+              .addReg(SpecialRegs->getStackPointerRegister())
+              .addImm(TFL->getBackchainOffset(*MF))
+              .addReg(0);
+
+    BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::STG))
+        .addReg(BCReg)
+        .addReg(BufReg)
+        .addImm(BCOffset)
+        .addReg(0);
+  }
+
+  // Setup.
+  MIB = BuildMI(*thisMBB, MI, DL, TII->get(SystemZ::EH_SjLj_Setup))
+            .addMBB(restoreMBB);
+
+  const SystemZRegisterInfo *RegInfo = Subtarget.getRegisterInfo();
+  MIB.addRegMask(RegInfo->getNoPreservedMask());
+
+  thisMBB->addSuccessor(mainMBB);
+  thisMBB->addSuccessor(restoreMBB);
+
+  // mainMBB:
+  BuildMI(mainMBB, DL, TII->get(SystemZ::LHI), mainDstReg).addImm(0);
+  mainMBB->addSuccessor(sinkMBB);
+
+  // sinkMBB:
+  BuildMI(*sinkMBB, sinkMBB->begin(), DL, TII->get(SystemZ::PHI), DstReg)
+      .addReg(mainDstReg)
+      .addMBB(mainMBB)
+      .addReg(restoreDstReg)
+      .addMBB(restoreMBB);
+
+  // restoreMBB.
+  BuildMI(restoreMBB, DL, TII->get(SystemZ::LHI), restoreDstReg).addImm(1);
+  BuildMI(restoreMBB, DL, TII->get(SystemZ::J)).addMBB(sinkMBB);
+  restoreMBB->addSuccessor(sinkMBB);
+
+  MI.eraseFromParent();
+
+  return sinkMBB;
+}
+
+MachineBasicBlock *
+SystemZTargetLowering::emitEHSjLjLongJmp(MachineInstr &MI,
+                                         MachineBasicBlock *MBB) const {
+
+  DebugLoc DL = MI.getDebugLoc();
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
+
+  MachineFunction *MF = MBB->getParent();
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+
+  MVT PVT = getPointerTy(MF->getDataLayout());
+  assert((PVT == MVT::i64 || PVT == MVT::i32) && "Invalid Pointer Size!");
+  Register BufReg = MI.getOperand(0).getReg();
+  const TargetRegisterClass *RC = MRI.getRegClass(BufReg);
+  auto *SpecialRegs = Subtarget.getSpecialRegisters();
+
+  Register Tmp = MRI.createVirtualRegister(RC);
+  Register BCReg = MRI.createVirtualRegister(RC);
+
+  MachineInstrBuilder MIB;
+
+  const int64_t FPOffset = 0;
+  const int64_t LabelOffset = 1 * PVT.getStoreSize();
+  const int64_t BCOffset = 2 * PVT.getStoreSize();
+  const int64_t SPOffset = 3 * PVT.getStoreSize();
+  const int64_t LPOffset = 4 * PVT.getStoreSize();
+
+  MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::LG), Tmp)
+            .addReg(BufReg)
+            .addImm(LabelOffset)
+            .addReg(0);
+
+  MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::LG),
+                SpecialRegs->getFramePointerRegister())
+            .addReg(BufReg)
+            .addImm(FPOffset)
+            .addReg(0);
+
+  // We are restoring R13 even though we never stored in setjmp from llvm,
+  // as gcc always stores R13 in builtin_setjmp. We could have mixed code
+  // gcc setjmp and llvm longjmp.
+  MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::LG), SystemZ::R13D)
+            .addReg(BufReg)
+            .addImm(LPOffset)
+            .addReg(0);
+
+  bool BackChain = MF->getSubtarget<SystemZSubtarget>().hasBackChain();
+  if (BackChain) {
+    MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::LG), BCReg)
+              .addReg(BufReg)
+              .addImm(BCOffset)
+              .addReg(0);
+  }
+
+  MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::LG),
+                SpecialRegs->getStackPointerRegister())
+            .addReg(BufReg)
+            .addImm(SPOffset)
+            .addReg(0);
+
+  if (BackChain) {
+    auto *TFL = Subtarget.getFrameLowering<SystemZFrameLowering>();
+    BuildMI(*MBB, MI, DL, TII->get(SystemZ::STG))
+        .addReg(BCReg)
+        .addReg(SpecialRegs->getStackPointerRegister())
+        .addImm(TFL->getBackchainOffset(*MF))
+        .addReg(0);
+  }
+
+  MIB = BuildMI(*MBB, MI, DL, TII->get(SystemZ::BR)).addReg(Tmp);
+
+  MI.eraseFromParent();
+  return MBB;
+}
+
 /// Returns true if stack probing through inline assembly is requested.
 bool SystemZTargetLowering::hasInlineStackProbe(const MachineFunction &MF) const {
   // If the function specifically requests inline stack probes, emit them.
@@ -6292,6 +6531,14 @@ SDValue SystemZTargetLowering::LowerOperation(SDValue Op,
     return lowerGET_ROUNDING(Op, DAG);
   case ISD::READCYCLECOUNTER:
     return lowerREADCYCLECOUNTER(Op, DAG);
+  case ISD::EH_SJLJ_SETJMP:
+  case ISD::EH_SJLJ_LONGJMP:
+    // These operations are legal on our platform, but we cannot actually
+    // set the operation action to Legal as common code would treat this
+    // as equivalent to Expand. Instead, we keep the operation action to
+    // Custom and just leave them unchanged here.
+    return Op;
+
   default:
     llvm_unreachable("Unexpected node to lower");
   }
@@ -9733,6 +9980,10 @@ MachineBasicBlock *SystemZTargetLowering::EmitInstrWithCustomInserter(
 
   case SystemZ::PROBED_ALLOCA:
     return emitProbedAlloca(MI, MBB);
+  case SystemZ::EH_SjLj_SetJmp:
+    return emitEHSjLjSetJmp(MI, MBB);
+  case SystemZ::EH_SjLj_LongJmp:
+    return emitEHSjLjLongJmp(MI, MBB);
 
   case TargetOpcode::STACKMAP:
   case TargetOpcode::PATCHPOINT:

llvm/lib/Target/SystemZ/SystemZISelLowering.h

@@ -476,6 +476,12 @@ class SystemZTargetLowering : public TargetLowering {
     // LD, and having the full constant in memory enables reg/mem opcodes.
     return VT != MVT::f64;
   }
+  MachineBasicBlock *emitEHSjLjSetJmp(MachineInstr &MI,
+                                      MachineBasicBlock *MBB) const;
+
+  MachineBasicBlock *emitEHSjLjLongJmp(MachineInstr &MI,
+                                       MachineBasicBlock *MBB) const;
+
   bool hasInlineStackProbe(const MachineFunction &MF) const override;
   AtomicExpansionKind shouldCastAtomicLoadInIR(LoadInst *LI) const override;
   AtomicExpansionKind shouldCastAtomicStoreInIR(StoreInst *SI) const override;

llvm/lib/Target/SystemZ/SystemZInstrInfo.td

@@ -1862,6 +1862,23 @@ let mayLoad = 1, mayStore = 1, Defs = [CC] in {
   }
 }
 
+//--------------------------------------------------------------------------
+// Setjmp/Longjmp.
+//--------------------------------------------------------------------------
+let isBarrier = 1,  hasNoSchedulingInfo = 1 in {
+  let hasSideEffects = 1, usesCustomInserter = 1 in {
+    def EH_SjLj_SetJmp : Pseudo<(outs GR32:$dst), (ins ADDR64:$R2), 
+                        [(set GR32:$dst, (z_eh_sjlj_setjmp ADDR64:$R2))]>;
+    let isTerminator = 1 in {
+      def EH_SjLj_LongJmp : Pseudo<(outs), (ins ADDR64:$R2), 
+                           [(z_eh_sjlj_longjmp  ADDR64:$R2)]>;
+    }
+  }
+  let isTerminator = 1, isCodeGenOnly = 1, Size = 0 in {
+    def EH_SjLj_Setup : Pseudo<(outs), (ins brtarget32:$dst), []>;
+  }
+}
+
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