diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -23355,10 +23355,13 @@
   int Index0, Index1;
   SDValue Src0 = DAG.getSplatSourceVector(N0, Index0);
   SDValue Src1 = DAG.getSplatSourceVector(N1, Index1);
+  // Extract element from splat_vector should be free.
+  bool IsBothSplatVector = N0.getOpcode() == ISD::SPLAT_VECTOR &&
+                           N1.getOpcode() == ISD::SPLAT_VECTOR;
   if (!Src0 || !Src1 || Index0 != Index1 ||
       Src0.getValueType().getVectorElementType() != EltVT ||
       Src1.getValueType().getVectorElementType() != EltVT ||
-      !TLI.isExtractVecEltCheap(VT, Index0) ||
+      !(IsBothSplatVector || TLI.isExtractVecEltCheap(VT, Index0)) ||
       !TLI.isOperationLegalOrCustom(Opcode, EltVT))
     return SDValue();
 
@@ -23380,6 +23383,8 @@
   }
 
   // bo (splat X, Index), (splat Y, Index) --> splat (bo X, Y), Index
+  if (VT.isScalableVector())
+    return DAG.getSplatVector(VT, DL, ScalarBO);
   SmallVector<SDValue, 8> Ops(VT.getVectorNumElements(), ScalarBO);
   return DAG.getBuildVector(VT, DL, Ops);
 }
diff --git a/llvm/test/CodeGen/RISCV/rvv/vadd-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vadd-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vadd-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vadd-sdnode.ll
@@ -879,9 +879,9 @@
 ;
 ; RV64-LABEL: vadd_xx_nxv8i64:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
+; RV64-NEXT:    add a0, a0, a1
+; RV64-NEXT:    vsetvli a1, zero, e64, m8, ta, mu
 ; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vadd.vx v8, v8, a1
 ; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
diff --git a/llvm/test/CodeGen/RISCV/rvv/vand-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vand-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vand-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vand-sdnode.ll
@@ -1370,9 +1370,9 @@
 ;
 ; RV64-LABEL: vand_xx_nxv8i64:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
+; RV64-NEXT:    and a0, a0, a1
+; RV64-NEXT:    vsetvli a1, zero, e64, m8, ta, mu
 ; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vand.vx v8, v8, a1
 ; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
diff --git a/llvm/test/CodeGen/RISCV/rvv/vmul-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vmul-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vmul-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vmul-sdnode.ll
@@ -938,13 +938,6 @@
 ; RV32-NEXT:    vmul.vv v8, v8, v16
 ; RV32-NEXT:    addi sp, sp, 16
 ; RV32-NEXT:    ret
-;
-; RV64-LABEL: vmul_xx_nxv8i64:
-; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
-; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vmul.vx v8, v8, a1
-; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
   %head2 = insertelement <vscale x 8 x i64> poison, i64 %b, i32 0
diff --git a/llvm/test/CodeGen/RISCV/rvv/vor-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vor-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vor-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vor-sdnode.ll
@@ -1163,9 +1163,9 @@
 ;
 ; RV64-LABEL: vor_xx_nxv8i64:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
+; RV64-NEXT:    or a0, a0, a1
+; RV64-NEXT:    vsetvli a1, zero, e64, m8, ta, mu
 ; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vor.vx v8, v8, a1
 ; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
diff --git a/llvm/test/CodeGen/RISCV/rvv/vsub-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vsub-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vsub-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vsub-sdnode.ll
@@ -857,9 +857,9 @@
 ;
 ; RV64-LABEL: vsub_xx_nxv8i64:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
+; RV64-NEXT:    sub a0, a0, a1
+; RV64-NEXT:    vsetvli a1, zero, e64, m8, ta, mu
 ; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vsub.vx v8, v8, a1
 ; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer
diff --git a/llvm/test/CodeGen/RISCV/rvv/vxor-sdnode.ll b/llvm/test/CodeGen/RISCV/rvv/vxor-sdnode.ll
--- a/llvm/test/CodeGen/RISCV/rvv/vxor-sdnode.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/vxor-sdnode.ll
@@ -1370,9 +1370,9 @@
 ;
 ; RV64-LABEL: vxor_xx_nxv8i64:
 ; RV64:       # %bb.0:
-; RV64-NEXT:    vsetvli a2, zero, e64, m8, ta, mu
+; RV64-NEXT:    xor a0, a0, a1
+; RV64-NEXT:    vsetvli a1, zero, e64, m8, ta, mu
 ; RV64-NEXT:    vmv.v.x v8, a0
-; RV64-NEXT:    vxor.vx v8, v8, a1
 ; RV64-NEXT:    ret
   %head1 = insertelement <vscale x 8 x i64> poison, i64 %a, i32 0
   %splat1 = shufflevector <vscale x 8 x i64> %head1, <vscale x 8 x i64> poison, <vscale x 8 x i32> zeroinitializer