diff --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.h
@@ -191,6 +191,7 @@
 struct RISCVMaskedPseudoInfo {
   uint16_t MaskedPseudo;
   uint16_t UnmaskedPseudo;
+  uint16_t UnmaskedTuPseudo;
   uint8_t MaskOpIdx;
 };
 
diff --git a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
--- a/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelDAGToDAG.cpp
@@ -2243,6 +2243,9 @@
 
   const MCInstrDesc &MaskedMCID = TII->get(N->getMachineOpcode());
 
+  // When turning allone-masked pseudo into an unmasked one,
+  // we assume policy operand precedes merge operand
+  bool IsTA = true;
   if (RISCVII::hasVecPolicyOp(MaskedMCID.TSFlags)) {
     // The last operand of the pseudo is the policy op, but we're expecting a
     // Glue operand last. We may also have a chain.
@@ -2252,24 +2255,40 @@
     if (N->getOperand(*TailPolicyOpIdx).getValueType() == MVT::Other)
       (*TailPolicyOpIdx)--;
 
-    // If the policy isn't TAIL_AGNOSTIC we can't perform this optimization.
-    if (N->getConstantOperandVal(*TailPolicyOpIdx) != RISCVII::TAIL_AGNOSTIC)
-      return false;
+    // If the tie operand is IMPLICIT_DEF, it is not preserved.
+    // So we turn it into _TU pseudos only when it is not IMPLICIT_DEF
+    if (N->getConstantOperandVal(*TailPolicyOpIdx) ==
+            RISCVII::TAIL_UNDISTURBED &&
+        !N->getOperand(0).isUndef())
+      IsTA = false;
   }
 
-  const MCInstrDesc &UnmaskedMCID = TII->get(I->UnmaskedPseudo);
+  if (IsTA) {
+    const MCInstrDesc &UnmaskedMCID = TII->get(I->UnmaskedPseudo);
 
-  // Check that we're dropping the merge operand, the mask operand, and any
-  // policy operand when we transform to this unmasked pseudo.
-  assert(!RISCVII::hasMergeOp(UnmaskedMCID.TSFlags) &&
-         RISCVII::hasDummyMaskOp(UnmaskedMCID.TSFlags) &&
-         !RISCVII::hasVecPolicyOp(UnmaskedMCID.TSFlags) &&
-         "Unexpected pseudo to transform to");
-  (void)UnmaskedMCID;
+    // Check that we're dropping the merge operand, the mask operand, and any
+    // policy operand when we transform to this unmasked pseudo.
+    assert(!RISCVII::hasMergeOp(UnmaskedMCID.TSFlags) &&
+           RISCVII::hasDummyMaskOp(UnmaskedMCID.TSFlags) &&
+           !RISCVII::hasVecPolicyOp(UnmaskedMCID.TSFlags) &&
+           "Unexpected pseudo to transform to");
+    (void)UnmaskedMCID;
+  } else {
+    const MCInstrDesc &UnmaskedTuMCID = TII->get(I->UnmaskedTuPseudo);
+
+    // Check that we're dropping the mask operand, and any policy operand
+    // when we transform to this unmasked tu pseudo.
+    assert(RISCVII::hasMergeOp(UnmaskedTuMCID.TSFlags) &&
+           RISCVII::hasDummyMaskOp(UnmaskedTuMCID.TSFlags) &&
+           !RISCVII::hasVecPolicyOp(UnmaskedTuMCID.TSFlags) &&
+           "Unexpected pseudo to transform to");
+    (void)UnmaskedTuMCID;
+  }
 
+  unsigned Opc = IsTA ? I->UnmaskedPseudo : I->UnmaskedTuPseudo;
   SmallVector<SDValue, 8> Ops;
-  // Skip the merge operand at index 0.
-  for (unsigned I = 1, E = N->getNumOperands(); I != E; I++) {
+  // Skip the merge operand at index 0 if IsTA
+  for (unsigned I = IsTA, E = N->getNumOperands(); I != E; I++) {
     // Skip the mask, the policy, and the Glue.
     SDValue Op = N->getOperand(I);
     if (I == MaskOpIdx || I == TailPolicyOpIdx ||
@@ -2282,8 +2301,7 @@
   if (auto *TGlued = Glued->getGluedNode())
     Ops.push_back(SDValue(TGlued, TGlued->getNumValues() - 1));
 
-  SDNode *Result =
-      CurDAG->getMachineNode(I->UnmaskedPseudo, SDLoc(N), N->getVTList(), Ops);
+  SDNode *Result = CurDAG->getMachineNode(Opc, SDLoc(N), N->getVTList(), Ops);
   ReplaceUses(N, Result);
 
   return true;
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td b/llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoVPseudos.td
@@ -426,13 +426,14 @@
 class RISCVMaskedPseudo<bits<4> MaskIdx> {
   Pseudo MaskedPseudo = !cast<Pseudo>(NAME);
   Pseudo UnmaskedPseudo = !cast<Pseudo>(!subst("_MASK", "", NAME));
+  Pseudo UnmaskedTuPseudo = !cast<Pseudo>(!subst("_MASK", "", NAME # "_TU"));
   bits<4> MaskOpIdx = MaskIdx;
 }
 
 def RISCVMaskedPseudosTable : GenericTable {
   let FilterClass = "RISCVMaskedPseudo";
   let CppTypeName = "RISCVMaskedPseudoInfo";
-  let Fields = ["MaskedPseudo", "UnmaskedPseudo", "MaskOpIdx"];
+  let Fields = ["MaskedPseudo", "UnmaskedPseudo", "UnmaskedTuPseudo", "MaskOpIdx"];
   let PrimaryKey = ["MaskedPseudo"];
   let PrimaryKeyName = "getMaskedPseudoInfo";
 }
diff --git a/llvm/test/CodeGen/RISCV/rvv/allone-masked-to-unmasked.ll b/llvm/test/CodeGen/RISCV/rvv/allone-masked-to-unmasked.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/rvv/allone-masked-to-unmasked.ll
@@ -0,0 +1,91 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv64 -mattr=+v -verify-machineinstrs < %s | FileCheck %s
+
+declare <vscale x 1 x i1> @llvm.riscv.vmset.nxv1i1(i64);
+
+declare <vscale x 1 x i8> @llvm.riscv.vadd.mask.nxv1i8.nxv1i8(
+  <vscale x 1 x i8>,
+  <vscale x 1 x i8>,
+  <vscale x 1 x i8>,
+  <vscale x 1 x i1>,
+  i64, i64);
+
+; Use unmasked instruction because the mask operand is allone mask;
+define <vscale x 1 x i8> @test0(<vscale x 1 x i8> %0, <vscale x 1 x i8> %1, i64 %2) nounwind {
+; CHECK-LABEL: test0:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e8, mf8, ta, mu
+; CHECK-NEXT:    vadd.vv v8, v8, v9
+; CHECK-NEXT:    ret
+entry:
+  %allone = call <vscale x 1 x i1> @llvm.riscv.vmset.nxv1i1(
+    i64 %2);
+  %a = call <vscale x 1 x i8> @llvm.riscv.vadd.mask.nxv1i8.nxv1i8(
+    <vscale x 1 x i8> undef,
+    <vscale x 1 x i8> %0,
+    <vscale x 1 x i8> %1,
+    <vscale x 1 x i1> %allone,
+    i64 %2, i64 1)
+
+  ret <vscale x 1 x i8> %a
+}
+
+; Regardless of the policy operand, TAIL_AGNOSIC is used because the tie operand is IMPLICIT_DEF
+define <vscale x 1 x i8> @test1(<vscale x 1 x i8> %0, <vscale x 1 x i8> %1, i64 %2) nounwind {
+; CHECK-LABEL: test1:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e8, mf8, ta, mu
+; CHECK-NEXT:    vadd.vv v8, v8, v9
+; CHECK-NEXT:    ret
+entry:
+  %allone = call <vscale x 1 x i1> @llvm.riscv.vmset.nxv1i1(
+    i64 %2);
+  %a = call <vscale x 1 x i8> @llvm.riscv.vadd.mask.nxv1i8.nxv1i8(
+    <vscale x 1 x i8> undef,
+    <vscale x 1 x i8> %0,
+    <vscale x 1 x i8> %1,
+    <vscale x 1 x i1> %allone,
+    i64 %2, i64 0)
+
+  ret <vscale x 1 x i8> %a
+}
+
+; Merge operand is kept because of the policy operand
+define <vscale x 1 x i8> @test2(<vscale x 1 x i8> %0, <vscale x 1 x i8> %1, <vscale x 1 x i8> %2, i64 %3) nounwind {
+; CHECK-LABEL: test2:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e8, mf8, tu, mu
+; CHECK-NEXT:    vadd.vv v8, v9, v10
+; CHECK-NEXT:    ret
+entry:
+  %allone = call <vscale x 1 x i1> @llvm.riscv.vmset.nxv1i1(
+    i64 %3);
+  %a = call <vscale x 1 x i8> @llvm.riscv.vadd.mask.nxv1i8.nxv1i8(
+    <vscale x 1 x i8> %0,
+    <vscale x 1 x i8> %1,
+    <vscale x 1 x i8> %2,
+    <vscale x 1 x i1> %allone,
+    i64 %3, i64 0)
+
+  ret <vscale x 1 x i8> %a
+}
+
+; Merge operand is dropped because of the policy operand
+define <vscale x 1 x i8> @test3(<vscale x 1 x i8> %0, <vscale x 1 x i8> %1, <vscale x 1 x i8> %2, i64 %3) nounwind {
+; CHECK-LABEL: test3:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    vsetvli zero, a0, e8, mf8, ta, mu
+; CHECK-NEXT:    vadd.vv v8, v9, v10
+; CHECK-NEXT:    ret
+entry:
+  %allone = call <vscale x 1 x i1> @llvm.riscv.vmset.nxv1i1(
+    i64 %3);
+  %a = call <vscale x 1 x i8> @llvm.riscv.vadd.mask.nxv1i8.nxv1i8(
+    <vscale x 1 x i8> %0,
+    <vscale x 1 x i8> %1,
+    <vscale x 1 x i8> %2,
+    <vscale x 1 x i1> %allone,
+    i64 %3, i64 1)
+
+  ret <vscale x 1 x i8> %a
+}