[RISC-V] Support __builtin_thread_pointer

[kamleshbhalui]

Summary

Fixes
https://bugs.llvm.org/show_bug.cgi?id=45303

[luismarques]

Please add tests.

[kamleshbhalui]

nit and Added the tests.

[luismarques]

LGTM. Thanks!

llvm/test/CodeGen/RISCV/pr45303.ll

1 ↗

(On Diff #252814)

Best to add a run line for rv32 too.

[kamleshbhalui]

Added rv32 run line.

@luismarques Thanks for the review.
I do not have commit access.

[lenary]

Please do not merge this until I have had the opportunity to ensure it works correctly with all threading models. I will approve it once I am satisfied this patch is correct.

[asb]

Thanks for the patch. I added a couple of nits - please rename the test file to thread-pointer.ll to match what other backends do and make it more discoverable. Also, although there different is minor we do use update_llc_test_checks.py for essentially all RISC-V tests so it would be good to use that for thread-pointer.ll as well.

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

841

Nit: Should be DL to match the variable naming elsewhere.

llvm/test/CodeGen/RISCV/pr45303.ll

1 ↗

(On Diff #252825)

We normally put the smallest triple that make sense. In this case, just riscv32 and riscv64 are sufficient to exhibit the bheaviour.

[luismarques]

llvm/test/CodeGen/RISCV/pr45303.ll

6 ↗

(On Diff #252825)

If you are going to use update_llc_test_checks.py then you should add nounwind, to avoid the CFI directives.

[kamleshbhalui]

nits and updated test.

[MaskRay]

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

2

Delete --check-prefix=CHECK

[kamleshbhalui]

nit test

[lenary]

After discussion with the RISC-V GCC Developers (including @kito-cheng), we have decided that both GCC and Clang will use __builtin_thread_pointer() to return the value in tp. I'm happy for this to land now.

[kamleshbhalui]

Thanks @lenary for review.
I do not have commit access,
please commit this when you get time.

llvm/lib/Target/RISCV/RISCVISelLowering.h

private:
   SDValue lowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerSELECT(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerVASTART(SDValue Op, SelectionDAG &DAG) const;
   SDValue lowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
   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,
       const SmallVector<CCValAssign, 16> &ArgLocs) const;
 
   TargetLowering::AtomicExpansionKind
   shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;
   virtual Value *emitMaskedAtomicRMWIntrinsic(

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   // TODO: On M-mode only targets, the cycle[h] CSR may not be present.
   // Unfortunately this can't be determined just from the ISA naming string.
   setOperationAction(ISD::READCYCLECOUNTER, MVT::i64,
                      Subtarget.is64Bit() ? Legal : Custom);
 
   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());
     setMinCmpXchgSizeInBits(32);
   } else {
     setMaxAtomicSizeInBitsSupported(0);
   }
 
case ISD::BITCAST: {
     SDLoc DL(Op);
     SDValue Op0 = Op.getOperand(0);
     if (Op.getValueType() != MVT::f32 || Op0.getValueType() != MVT::i32)
       return SDValue();
     SDValue NewOp0 = DAG.getNode(ISD::ANY_EXTEND, DL, MVT::i64, Op0);
     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);
   }
 }
 
 static SDValue getTargetNode(GlobalAddressSDNode *N, SDLoc DL, EVT Ty,
                              SelectionDAG &DAG, unsigned Flags) {
   return DAG.getTargetGlobalAddress(N->getGlobal(), DL, Ty, 0, Flags);
 }
 
SDValue RISCVTargetLowering::lowerShiftRightParts(SDValue Op, SelectionDAG &DAG,
 
   Lo = DAG.getNode(ISD::SELECT, DL, VT, CC, LoTrue, LoFalse);
   Hi = DAG.getNode(ISD::SELECT, DL, VT, CC, HiTrue, HiFalse);
 
   SDValue Parts[2] = {Lo, Hi};
   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) {
   switch (Opcode) {
   default:
     llvm_unreachable("Unexpected opcode");
   case ISD::SHL:
     return RISCVISD::SLLW;

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

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=riscv64 | FileCheck %s --check-prefix=CHECK
+; RUN: llc < %s -mtriple=riscv32 | FileCheck %s --check-prefix=CHECK
+
+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
+}