[LoongArch] Support llvm.thread.pointer

[xen0n]

Summary

For __builtin_thread_pointer to work, among other things.

Similar to D76828 for RISCV.

[xen0n]

change commit message

[xry111]

It's straightforward enough IMO.

llvm/lib/Target/LoongArch/LoongArchISelLowering.h

private:
   EmitInstrWithCustomInserter(MachineInstr &MI,
                               MachineBasicBlock *BB) const override;
   SDValue lowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerEH_DWARF_CFA(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFP_TO_SINT(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerBITCAST(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerUINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerVASTART(SDValue Op, SelectionDAG &DAG) const;
+  SDValue lowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
 
   bool isFPImmLegal(const APFloat &Imm, EVT VT,
                     bool ForCodeSize) const override;
 
   bool shouldInsertFencesForAtomic(const Instruction *I) const override;
 
   ConstraintType getConstraintType(StringRef Constraint) const override;
 

llvm/lib/Target/LoongArch/LoongArchISelLowering.cpp

LoongArchTargetLowering::LoongArchTargetLowering(const TargetMachine &TM,
   setOperationAction(ISD::SRA_PARTS, GRLenVT, Custom);
   setOperationAction(ISD::SRL_PARTS, GRLenVT, Custom);
   setOperationAction(ISD::FP_TO_SINT, GRLenVT, Custom);
   setOperationAction(ISD::ROTL, GRLenVT, Expand);
   setOperationAction(ISD::CTPOP, GRLenVT, Expand);
 
   setOperationAction({ISD::GlobalAddress, ISD::ConstantPool}, GRLenVT, Custom);
 
+  setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
+
   setOperationAction(ISD::EH_DWARF_CFA, MVT::i32, Custom);
   if (Subtarget.is64Bit())
     setOperationAction(ISD::EH_DWARF_CFA, MVT::i64, Custom);
 
   setOperationAction(ISD::DYNAMIC_STACKALLOC, GRLenVT, Expand);
   setOperationAction(ISD::VASTART, MVT::Other, Custom);
   setOperationAction({ISD::VAARG, ISD::VACOPY, ISD::VAEND}, MVT::Other, Expand);
 

 
 SDValue LoongArchTargetLowering::LowerOperation(SDValue Op,
                                                 SelectionDAG &DAG) const {
   switch (Op.getOpcode()) {
   case ISD::EH_DWARF_CFA:
     return lowerEH_DWARF_CFA(Op, DAG);
   case ISD::GlobalAddress:
     return lowerGlobalAddress(Op, DAG);
+  case ISD::INTRINSIC_WO_CHAIN:
+    return lowerINTRINSIC_WO_CHAIN(Op, DAG);
   case ISD::SHL_PARTS:
     return lowerShiftLeftParts(Op, DAG);
   case ISD::SRA_PARTS:
     return lowerShiftRightParts(Op, DAG, true);
   case ISD::SRL_PARTS:
     return lowerShiftRightParts(Op, DAG, false);
   case ISD::ConstantPool:
     return lowerConstantPool(Op, DAG);
SDValue GALo =
         DAG.getTargetGlobalAddress(GV, DL, Ty, 0, LoongArchII::MO_PCREL_LO);
     SDValue AddrHi(DAG.getMachineNode(LoongArch::PCALAU12I, DL, Ty, GAHi), 0);
 
     return SDValue(DAG.getMachineNode(ADDIOp, DL, Ty, AddrHi, GALo), 0);
   }
   report_fatal_error("Unable to lowerGlobalAddress");
 }
 
+SDValue LoongArchTargetLowering::lowerINTRINSIC_WO_CHAIN(SDValue Op,
+                                                         SelectionDAG &DAG) const {
+  unsigned IntNo = Op.getConstantOperandVal(0);
+
+  switch (IntNo) {
+  default:
+    return SDValue(); // Don't custom lower most intrinsics.
+  case Intrinsic::thread_pointer: {
+    EVT PtrVT = getPointerTy(DAG.getDataLayout());
+    return DAG.getRegister(LoongArch::R2, PtrVT);
+  }
+  }
+}
+
 SDValue LoongArchTargetLowering::lowerShiftLeftParts(SDValue Op,
                                                      SelectionDAG &DAG) const {
   SDLoc DL(Op);
   SDValue Lo = Op.getOperand(0);
   SDValue Hi = Op.getOperand(1);
   SDValue Shamt = Op.getOperand(2);
   EVT VT = Lo.getValueType();
 

llvm/test/CodeGen/LoongArch/thread-pointer.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s --mtriple=loongarch32 | FileCheck %s
+; RUN: llc < %s --mtriple=loongarch64 | FileCheck %s
+
+declare ptr @llvm.thread.pointer()
+
+define ptr @thread_pointer() nounwind {
+; CHECK-LABEL: thread_pointer:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    move $a0, $tp
+; CHECK-NEXT:    ret
+  %1 = tail call ptr @llvm.thread.pointer()
+  ret ptr %1
+}