Index: lib/Target/RISCV/RISCVISelLowering.h
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.h
+++ lib/Target/RISCV/RISCVISelLowering.h
@@ -110,6 +110,12 @@
     return ISD::SIGN_EXTEND;
   }
 
+  bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override {
+    if (DAG.getMachineFunction().getFunction().optForMinSize())
+      return false;
+    return true;
+  }
+
 private:
   void analyzeInputArgs(MachineFunction &MF, CCState &CCInfo,
                         const SmallVectorImpl<ISD::InputArg> &Ins,
@@ -144,6 +150,8 @@
   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;
 
   bool isEligibleForTailCallOptimization(
       CCState &CCInfo, CallLoweringInfo &CLI, MachineFunction &MF,
Index: lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- lib/Target/RISCV/RISCVISelLowering.cpp
+++ lib/Target/RISCV/RISCVISelLowering.cpp
@@ -113,9 +113,9 @@
   setOperationAction(ISD::SMUL_LOHI, XLenVT, Expand);
   setOperationAction(ISD::UMUL_LOHI, XLenVT, Expand);
 
-  setOperationAction(ISD::SHL_PARTS, XLenVT, Expand);
-  setOperationAction(ISD::SRL_PARTS, XLenVT, Expand);
-  setOperationAction(ISD::SRA_PARTS, XLenVT, Expand);
+  setOperationAction(ISD::SHL_PARTS, XLenVT, Custom);
+  setOperationAction(ISD::SRL_PARTS, XLenVT, Custom);
+  setOperationAction(ISD::SRA_PARTS, XLenVT, Custom);
 
   setOperationAction(ISD::ROTL, XLenVT, Expand);
   setOperationAction(ISD::ROTR, XLenVT, Expand);
@@ -348,6 +348,12 @@
     return lowerFRAMEADDR(Op, DAG);
   case ISD::RETURNADDR:
     return lowerRETURNADDR(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::BITCAST: {
     assert(Subtarget.is64Bit() && Subtarget.hasStdExtF() &&
            "Unexpected custom legalisation");
@@ -538,6 +544,97 @@
   return DAG.getCopyFromReg(DAG.getEntryNode(), DL, Reg, XLenVT);
 }
 
+SDValue RISCVTargetLowering::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();
+
+  // if Shamt-XLEN < 0: // Shamt < XLEN
+  //   Lo = Lo << (Shamt-XLEN)
+  //   Hi = (Hi << Shamt) | ((Lo >>u 1) >>u (XLEN-1 - Shamt))
+  // else:
+  //   Lo = 0
+  //   Hi = Lo << Shamt
+
+  SDValue Zero = DAG.getConstant(0, DL, VT);
+  SDValue One = DAG.getConstant(1, DL, VT);
+  SDValue MinusXLen = DAG.getConstant(-Subtarget.getXLen(), DL, VT);
+  SDValue XLenMinus1 = DAG.getConstant(Subtarget.getXLen() - 1, DL, VT);
+  SDValue ShamtMinusXLen = DAG.getNode(ISD::ADD, DL, VT, Shamt, MinusXLen);
+  SDValue XLenMinus1Shamt = DAG.getNode(ISD::SUB, DL, VT, XLenMinus1, Shamt);
+
+  SDValue LoTrue = DAG.getNode(ISD::SHL, DL, VT, Lo, Shamt);
+  SDValue ShiftRight1Lo = DAG.getNode(ISD::SRL, DL, VT, Lo, One);
+  SDValue ShiftRightLo =
+      DAG.getNode(ISD::SRL, DL, VT, ShiftRight1Lo, XLenMinus1Shamt);
+  SDValue ShiftLeftHi = DAG.getNode(ISD::SHL, DL, VT, Hi, Shamt);
+  SDValue HiTrue = DAG.getNode(ISD::OR, DL, VT, ShiftLeftHi, ShiftRightLo);
+  SDValue HiFalse = DAG.getNode(ISD::SHL, DL, VT, Lo, ShamtMinusXLen);
+
+  SDValue CC = DAG.getSetCC(DL, VT, ShamtMinusXLen, Zero, ISD::SETLT);
+
+  Lo = DAG.getNode(ISD::SELECT, DL, VT, CC, LoTrue, Zero);
+  Hi = DAG.getNode(ISD::SELECT, DL, VT, CC, HiTrue, HiFalse);
+
+  SDValue Parts[2] = {Lo, Hi};
+  return DAG.getMergeValues(Parts, DL);
+}
+
+SDValue RISCVTargetLowering::lowerShiftRightParts(SDValue Op, SelectionDAG &DAG,
+                                                  bool IsSRA) const {
+  SDLoc DL(Op);
+  SDValue Lo = Op.getOperand(0);
+  SDValue Hi = Op.getOperand(1);
+  SDValue Shamt = Op.getOperand(2);
+  EVT VT = Lo.getValueType();
+
+  // SRA expansion:
+  //   if Shamt-XLEN < 0: // Shamt < XLEN
+  //     Lo = (Lo >>u Shamt) | ((Hi << 1) << (XLEN-1 - Shamt))
+  //     Hi = Hi >>s Shamt
+  //   else:
+  //     Lo = Hi >>s (Shamt-XLEN);
+  //     Hi = Hi >>s (XLEN-1)
+  //
+  // SRL expansion:
+  //   if Shamt-XLEN < 0: // Shamt < XLEN
+  //     Lo = (Lo >>u Shamt) | ((Hi << 1) << (XLEN-1 - Shamt))
+  //     Hi = Hi >>u Shamt
+  //   else:
+  //     Lo = Hi >>u (Shamt-XLEN);
+  //     Hi = 0;
+
+  unsigned ShiftRightOp = IsSRA ? ISD::SRA : ISD::SRL;
+
+  SDValue Zero = DAG.getConstant(0, DL, VT);
+  SDValue One = DAG.getConstant(1, DL, VT);
+  SDValue MinusXLen = DAG.getConstant(-Subtarget.getXLen(), DL, VT);
+  SDValue XLenMinus1 = DAG.getConstant(Subtarget.getXLen() - 1, DL, VT);
+  SDValue ShamtMinusXLen = DAG.getNode(ISD::ADD, DL, VT, Shamt, MinusXLen);
+  SDValue XLenMinus1Shamt = DAG.getNode(ISD::SUB, DL, VT, XLenMinus1, Shamt);
+
+  SDValue ShiftRightLo = DAG.getNode(ISD::SRL, DL, VT, Lo, Shamt);
+  SDValue ShiftLeftHi1 = DAG.getNode(ISD::SHL, DL, VT, Hi, One);
+  SDValue ShiftLeftHi =
+      DAG.getNode(ISD::SHL, DL, VT, ShiftLeftHi1, XLenMinus1Shamt);
+  SDValue LoTrue = DAG.getNode(ISD::OR, DL, VT, ShiftRightLo, ShiftLeftHi);
+  SDValue HiTrue = DAG.getNode(ShiftRightOp, DL, VT, Hi, Shamt);
+  SDValue LoFalse = DAG.getNode(ShiftRightOp, DL, VT, Hi, ShamtMinusXLen);
+  SDValue HiFalse =
+      IsSRA ? DAG.getNode(ISD::SRA, DL, VT, Hi, XLenMinus1) : Zero;
+
+  SDValue CC = DAG.getSetCC(DL, VT, ShamtMinusXLen, Zero, ISD::SETLT);
+
+  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);
+}
+
 // Returns the opcode of the target-specific SDNode that implements the 32-bit
 // form of the given Opcode.
 static RISCVISD::NodeType getRISCVWOpcode(unsigned Opcode) {
Index: test/CodeGen/RISCV/alu64.ll
===================================================================
--- test/CodeGen/RISCV/alu64.ll
+++ test/CodeGen/RISCV/alu64.ll
@@ -211,11 +211,20 @@
 ;
 ; RV32I-LABEL: sll:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __ashldi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB11_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    sll a1, a0, a3
+; RV32I-NEXT:    mv a0, zero
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB11_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    srli a4, a0, 1
+; RV32I-NEXT:    srl a3, a4, a3
+; RV32I-NEXT:    sll a1, a1, a2
+; RV32I-NEXT:    or a1, a1, a3
+; RV32I-NEXT:    sll a0, a0, a2
 ; RV32I-NEXT:    ret
   %1 = shl i64 %a, %b
   ret i64 %1
@@ -288,11 +297,20 @@
 ;
 ; RV32I-LABEL: srl:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __lshrdi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB15_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    srl a0, a1, a3
+; RV32I-NEXT:    mv a1, zero
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB15_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    slli a4, a1, 1
+; RV32I-NEXT:    sll a3, a4, a3
+; RV32I-NEXT:    srl a0, a0, a2
+; RV32I-NEXT:    or a0, a0, a3
+; RV32I-NEXT:    srl a1, a1, a2
 ; RV32I-NEXT:    ret
   %1 = lshr i64 %a, %b
   ret i64 %1
@@ -306,11 +324,20 @@
 ;
 ; RV32I-LABEL: sra:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __ashrdi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB16_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    sra a0, a1, a3
+; RV32I-NEXT:    srai a1, a1, 31
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB16_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    slli a4, a1, 1
+; RV32I-NEXT:    sll a3, a4, a3
+; RV32I-NEXT:    srl a0, a0, a2
+; RV32I-NEXT:    or a0, a0, a3
+; RV32I-NEXT:    sra a1, a1, a2
 ; RV32I-NEXT:    ret
   %1 = ashr i64 %a, %b
   ret i64 %1
Index: test/CodeGen/RISCV/shifts.ll
===================================================================
--- test/CodeGen/RISCV/shifts.ll
+++ test/CodeGen/RISCV/shifts.ll
@@ -8,11 +8,20 @@
 define i64 @lshr64(i64 %a, i64 %b) nounwind {
 ; RV32I-LABEL: lshr64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __lshrdi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB0_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    srl a0, a1, a3
+; RV32I-NEXT:    mv a1, zero
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB0_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    slli a4, a1, 1
+; RV32I-NEXT:    sll a3, a4, a3
+; RV32I-NEXT:    srl a0, a0, a2
+; RV32I-NEXT:    or a0, a0, a3
+; RV32I-NEXT:    srl a1, a1, a2
 ; RV32I-NEXT:    ret
   %1 = lshr i64 %a, %b
   ret i64 %1
@@ -21,11 +30,20 @@
 define i64 @ashr64(i64 %a, i64 %b) nounwind {
 ; RV32I-LABEL: ashr64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __ashrdi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB1_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    sra a0, a1, a3
+; RV32I-NEXT:    srai a1, a1, 31
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB1_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    slli a4, a1, 1
+; RV32I-NEXT:    sll a3, a4, a3
+; RV32I-NEXT:    srl a0, a0, a2
+; RV32I-NEXT:    or a0, a0, a3
+; RV32I-NEXT:    sra a1, a1, a2
 ; RV32I-NEXT:    ret
   %1 = ashr i64 %a, %b
   ret i64 %1
@@ -34,11 +52,20 @@
 define i64 @shl64(i64 %a, i64 %b) nounwind {
 ; RV32I-LABEL: shl64:
 ; RV32I:       # %bb.0:
-; RV32I-NEXT:    addi sp, sp, -16
-; RV32I-NEXT:    sw ra, 12(sp)
-; RV32I-NEXT:    call __ashldi3
-; RV32I-NEXT:    lw ra, 12(sp)
-; RV32I-NEXT:    addi sp, sp, 16
+; RV32I-NEXT:    addi a3, a2, -32
+; RV32I-NEXT:    bltz a3, .LBB2_2
+; RV32I-NEXT:  # %bb.1:
+; RV32I-NEXT:    sll a1, a0, a3
+; RV32I-NEXT:    mv a0, zero
+; RV32I-NEXT:    ret
+; RV32I-NEXT:  .LBB2_2:
+; RV32I-NEXT:    addi a3, zero, 31
+; RV32I-NEXT:    sub a3, a3, a2
+; RV32I-NEXT:    srli a4, a0, 1
+; RV32I-NEXT:    srl a3, a4, a3
+; RV32I-NEXT:    sll a1, a1, a2
+; RV32I-NEXT:    or a1, a1, a3
+; RV32I-NEXT:    sll a0, a0, a2
 ; RV32I-NEXT:    ret
   %1 = shl i64 %a, %b
   ret i64 %1