[RISCV] Support llvm.thread.pointer

Fixes https://bugs.llvm.org/show_bug.cgi?id=45303 (clang crashed on __builtin_thread_pointer)

Reviewed By: lenary, MaskRay, luismarques

Differential Revision: https://reviews.llvm.org/D76828

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -210,6 +210,7 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   setOperationAction(ISD::TRAP, MVT::Other, Legal);
   setOperationAction(ISD::DEBUGTRAP, MVT::Other, Legal);
+  setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::Other, Custom);
 
   if (Subtarget.hasStdExtA()) {
     setMaxAtomicSizeInBitsSupported(Subtarget.getXLen());
@@ -429,6 +430,8 @@ SDValue RISCVTargetLowering::LowerOperation(SDValue Op,
     SDValue FPConv = DAG.getNode(RISCVISD::FMV_W_X_RV64, DL, MVT::f32, NewOp0);
     return FPConv;
   }
+  case ISD::INTRINSIC_WO_CHAIN:
+    return LowerINTRINSIC_WO_CHAIN(Op, DAG);
   }
 }
 
@@ -832,6 +835,20 @@ SDValue RISCVTargetLowering::lowerShiftRightParts(SDValue Op, SelectionDAG &DAG,
   return DAG.getMergeValues(Parts, DL);
 }
 
+SDValue RISCVTargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
+                                                     SelectionDAG &DAG) const {
+  unsigned IntNo = cast<ConstantSDNode>(Op.getOperand(0))->getZExtValue();
+  SDLoc DL(Op);
+  switch (IntNo) {
+  default:
+    return SDValue();    // Don't custom lower most intrinsics.
+  case Intrinsic::thread_pointer: {
+    EVT PtrVT = getPointerTy(DAG.getDataLayout());
+    return DAG.getRegister(RISCV::X4, PtrVT);
+  }
+  }
+}
+
 // Returns the opcode of the target-specific SDNode that implements the 32-bit
 // form of the given Opcode.
 static RISCVISD::NodeType getRISCVWOpcode(unsigned Opcode) {

llvm/lib/Target/RISCV/RISCVISelLowering.h

@@ -203,6 +203,7 @@ class RISCVTargetLowering : public TargetLowering {
   SDValue lowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerShiftLeftParts(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerShiftRightParts(SDValue Op, SelectionDAG &DAG, bool IsSRA) const;
+  SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
 
   bool isEligibleForTailCallOptimization(
       CCState &CCInfo, CallLoweringInfo &CLI, MachineFunction &MF,

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

@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=riscv64 | FileCheck %s
+; RUN: llc < %s -mtriple=riscv32 | FileCheck %s
+
+declare i8* @llvm.thread.pointer()
+
+define i8* @thread_pointer() nounwind {
+; CHECK-LABEL: thread_pointer:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    mv a0, tp
+; CHECK-NEXT:    ret
+  %1 = tail call i8* @llvm.thread.pointer()
+  ret i8* %1
+}