diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6157,6 +6157,11 @@
     break;
   case ISD::VECTOR_SHUFFLE:
     llvm_unreachable("should use getVectorShuffle constructor!");
+  case ISD::VECTOR_SPLICE: {
+    if (cast<ConstantSDNode>(N3)->isNullValue())
+      return N1;
+    break;
+  }
   case ISD::INSERT_VECTOR_ELT: {
     ConstantSDNode *N3C = dyn_cast<ConstantSDNode>(N3);
     // INSERT_VECTOR_ELT into out-of-bounds element is an UNDEF, except
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -7630,11 +7630,14 @@
 
 SDValue AArch64TargetLowering::LowerVECTOR_SPLICE(SDValue Op,
                                                   SelectionDAG &DAG) const {
-
   EVT Ty = Op.getValueType();
   auto Idx = Op.getConstantOperandAPInt(2);
-  if (Idx.sge(-1) && Idx.slt(Ty.getVectorMinNumElements()))
+
+  // This will select to an EXT instruction, which has a maximum immediate
+  // value of 255, hence 2048-bits is the maximum value we can lower.
+  if (Idx.sge(-1) && Idx.slt(2048 / Ty.getVectorElementType().getSizeInBits()))
     return Op;
+
   return SDValue();
 }
 
diff --git a/llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td b/llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td
--- a/llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td
@@ -2598,14 +2598,14 @@
   }
 
   // Splice with lane bigger or equal to 0
-  def : Pat<(nxv16i8 (vector_splice (nxv16i8 ZPR:$Z1), (nxv16i8 ZPR:$Z2), (i64 (sve_ext_imm_0_15 i32:$index)))),
-            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_15:$index)>;
-  def : Pat<(nxv8i16 (vector_splice (nxv8i16 ZPR:$Z1), (nxv8i16 ZPR:$Z2), (i64 (sve_ext_imm_0_7 i32:$index)))),
-            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_7:$index)>;
-  def : Pat<(nxv4i32 (vector_splice (nxv4i32 ZPR:$Z1), (nxv4i32 ZPR:$Z2), (i64 (sve_ext_imm_0_3 i32:$index)))),
-            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_3:$index)>;
-  def : Pat<(nxv2i64 (vector_splice (nxv2i64 ZPR:$Z1), (nxv2i64 ZPR:$Z2), (i64 (sve_ext_imm_0_1 i32:$index)))),
-            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_1:$index)>;
+  def : Pat<(nxv16i8 (vector_splice (nxv16i8 ZPR:$Z1), (nxv16i8 ZPR:$Z2), (i64 (sve_ext_imm_0_255 i32:$index)))),
+            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_255:$index)>;
+  def : Pat<(nxv8i16 (vector_splice (nxv8i16 ZPR:$Z1), (nxv8i16 ZPR:$Z2), (i64 (sve_ext_imm_0_127 i32:$index)))),
+            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_127:$index)>;
+  def : Pat<(nxv4i32 (vector_splice (nxv4i32 ZPR:$Z1), (nxv4i32 ZPR:$Z2), (i64 (sve_ext_imm_0_63 i32:$index)))),
+            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_63:$index)>;
+  def : Pat<(nxv2i64 (vector_splice (nxv2i64 ZPR:$Z1), (nxv2i64 ZPR:$Z2), (i64 (sve_ext_imm_0_31 i32:$index)))),
+            (EXT_ZZI  ZPR:$Z1, ZPR:$Z2, sve_ext_imm_0_31:$index)>;
 
 } // End HasSVEorStreamingSVE
 
diff --git a/llvm/lib/Target/AArch64/SVEInstrFormats.td b/llvm/lib/Target/AArch64/SVEInstrFormats.td
--- a/llvm/lib/Target/AArch64/SVEInstrFormats.td
+++ b/llvm/lib/Target/AArch64/SVEInstrFormats.td
@@ -264,10 +264,10 @@
 def sve_cnt_shl_imm : ComplexPattern<i32, 1, "SelectCntImm<1, 16, 1, true>">;
 
 
-def sve_ext_imm_0_1  : ComplexPattern<i32, 1, "SelectEXTImm<1, 8>">;
-def sve_ext_imm_0_3  : ComplexPattern<i32, 1, "SelectEXTImm<3, 4>">;
-def sve_ext_imm_0_7  : ComplexPattern<i32, 1, "SelectEXTImm<7, 2>">;
-def sve_ext_imm_0_15 : ComplexPattern<i32, 1, "SelectEXTImm<15, 1>">;
+def sve_ext_imm_0_31  : ComplexPattern<i32, 1, "SelectEXTImm<31, 8>">;
+def sve_ext_imm_0_63  : ComplexPattern<i32, 1, "SelectEXTImm<63, 4>">;
+def sve_ext_imm_0_127 : ComplexPattern<i32, 1, "SelectEXTImm<127, 2>">;
+def sve_ext_imm_0_255 : ComplexPattern<i32, 1, "SelectEXTImm<255, 1>">;
 
 def int_aarch64_sve_cntp_oneuse : PatFrag<(ops node:$pred, node:$src2),
                                           (int_aarch64_sve_cntp node:$pred, node:$src2), [{
diff --git a/llvm/test/CodeGen/AArch64/named-vector-shuffles-sve.ll b/llvm/test/CodeGen/AArch64/named-vector-shuffles-sve.ll
--- a/llvm/test/CodeGen/AArch64/named-vector-shuffles-sve.ll
+++ b/llvm/test/CodeGen/AArch64/named-vector-shuffles-sve.ll
@@ -7,25 +7,33 @@
 ; VECTOR_SPLICE (index)
 ;
 
+define <vscale x 16 x i8> @splice_nxv16i8_zero_idx(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b) #0 {
+; CHECK-LABEL: splice_nxv16i8_zero_idx:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    ret
+  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 0)
+  ret <vscale x 16 x i8> %res
+}
+
 define <vscale x 16 x i8> @splice_nxv16i8_first_idx(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b) #0 {
 ; CHECK-LABEL: splice_nxv16i8_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #1
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 0)
+  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 1)
   ret <vscale x 16 x i8> %res
 }
 
 define <vscale x 16 x i8> @splice_nxv16i8_last_idx(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b) #0 {
 ; CHECK-LABEL: splice_nxv16i8_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #15
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #255
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 15)
+  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 255)
   ret <vscale x 16 x i8> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 16 x i8> @splice_nxv16i8_clamped_idx(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b) #0 {
 ; CHECK-LABEL: splice_nxv16i8_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -35,8 +43,8 @@
 ; CHECK-NEXT:    sub x9, x9, #1
 ; CHECK-NEXT:    ptrue p0.b
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w10, #16
-; CHECK-NEXT:    cmp x9, #16
+; CHECK-NEXT:    mov w10, #256
+; CHECK-NEXT:    cmp x9, #256
 ; CHECK-NEXT:    st1b { z0.b }, p0, [sp]
 ; CHECK-NEXT:    st1b { z1.b }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x9, x10, lo
@@ -44,29 +52,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 16)
+  %res = call <vscale x 16 x i8> @llvm.experimental.vector.splice.nxv16i8(<vscale x 16 x i8> %a, <vscale x 16 x i8> %b, i32 256)
   ret <vscale x 16 x i8> %res
 }
 
 define <vscale x 8 x i16> @splice_nxv8i16_first_idx(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b) #0 {
 ; CHECK-LABEL: splice_nxv8i16_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #2
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 0)
+  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 1)
   ret <vscale x 8 x i16> %res
 }
 
 define <vscale x 8 x i16> @splice_nxv8i16_last_idx(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b) #0 {
 ; CHECK-LABEL: splice_nxv8i16_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #14
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #254
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 7)
+  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 127)
   ret <vscale x 8 x i16> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 8 x i16> @splice_nxv8i16_clamped_idx(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b) #0 {
 ; CHECK-LABEL: splice_nxv8i16_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -76,8 +84,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.h
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #8
-; CHECK-NEXT:    cmp x10, #8
+; CHECK-NEXT:    mov w9, #128
+; CHECK-NEXT:    cmp x10, #128
 ; CHECK-NEXT:    st1h { z0.h }, p0, [sp]
 ; CHECK-NEXT:    st1h { z1.h }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -85,29 +93,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 8)
+  %res = call <vscale x 8 x i16> @llvm.experimental.vector.splice.nxv8i16(<vscale x 8 x i16> %a, <vscale x 8 x i16> %b, i32 128)
   ret <vscale x 8 x i16> %res
 }
 
 define <vscale x 4 x i32> @splice_nxv4i32_first_idx(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b) #0 {
 ; CHECK-LABEL: splice_nxv4i32_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #4
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 0)
+  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 1)
   ret <vscale x 4 x i32> %res
 }
 
 define <vscale x 4 x i32> @splice_nxv4i32_last_idx(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b) #0 {
 ; CHECK-LABEL: splice_nxv4i32_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #12
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #252
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 3)
+  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 63)
   ret <vscale x 4 x i32> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 4 x i32> @splice_nxv4i32_clamped_idx(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b) #0 {
 ; CHECK-LABEL: splice_nxv4i32_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -117,8 +125,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.s
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #4
-; CHECK-NEXT:    cmp x10, #4
+; CHECK-NEXT:    mov w9, #64
+; CHECK-NEXT:    cmp x10, #64
 ; CHECK-NEXT:    st1w { z0.s }, p0, [sp]
 ; CHECK-NEXT:    st1w { z1.s }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -126,29 +134,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 4)
+  %res = call <vscale x 4 x i32> @llvm.experimental.vector.splice.nxv4i32(<vscale x 4 x i32> %a, <vscale x 4 x i32> %b, i32 64)
   ret <vscale x 4 x i32> %res
 }
 
 define <vscale x 2 x i64> @splice_nxv2i64_first_idx(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b) #0 {
 ; CHECK-LABEL: splice_nxv2i64_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 0)
+  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 1)
   ret <vscale x 2 x i64> %res
 }
 
 define <vscale x 2 x i64> @splice_nxv2i64_last_idx(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b) #0 {
 ; CHECK-LABEL: splice_nxv2i64_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #248
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 1)
+  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 31)
   ret <vscale x 2 x i64> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 2 x i64> @splice_nxv2i64_clamped_idx(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b) #0 {
 ; CHECK-LABEL: splice_nxv2i64_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -158,8 +166,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.d
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #2
-; CHECK-NEXT:    cmp x10, #2
+; CHECK-NEXT:    mov w9, #32
+; CHECK-NEXT:    cmp x10, #32
 ; CHECK-NEXT:    st1d { z0.d }, p0, [sp]
 ; CHECK-NEXT:    st1d { z1.d }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -167,7 +175,7 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 2)
+  %res = call <vscale x 2 x i64> @llvm.experimental.vector.splice.nxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b, i32 32)
   ret <vscale x 2 x i64> %res
 }
 
@@ -205,31 +213,31 @@
 define <vscale x 2 x half> @splice_nxv2f16_first_idx(<vscale x 2 x half> %a, <vscale x 2 x half> %b) #0 {
 ; CHECK-LABEL: splice_nxv2f16_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 0)
+  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 1)
   ret <vscale x 2 x half> %res
 }
 
-define <vscale x 2 x half> @splice_nxv2f16_1_idx(<vscale x 2 x half> %a, <vscale x 2 x half> %b) #0 {
-; CHECK-LABEL: splice_nxv2f16_1_idx:
+define <vscale x 2 x half> @splice_nxv2f16_last_idx(<vscale x 2 x half> %a, <vscale x 2 x half> %b) #0 {
+; CHECK-LABEL: splice_nxv2f16_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #248
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 1)
+  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 31)
   ret <vscale x 2 x half> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
-define <vscale x 2 x half> @splice_nxv2f16_last_idx(<vscale x 2 x half> %a, <vscale x 2 x half> %b) #0 {
-; CHECK-LABEL: splice_nxv2f16_last_idx:
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
+define <vscale x 2 x half> @splice_nxv2f16_clamped_idx(<vscale x 2 x half> %a, <vscale x 2 x half> %b) #0 {
+; CHECK-LABEL: splice_nxv2f16_clamped_idx:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    str x29, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    addvl sp, sp, #-2
 ; CHECK-NEXT:    cntd x10
 ; CHECK-NEXT:    sub x10, x10, #1
-; CHECK-NEXT:    mov w9, #2
-; CHECK-NEXT:    cmp x10, #2
+; CHECK-NEXT:    mov w9, #32
+; CHECK-NEXT:    cmp x10, #32
 ; CHECK-NEXT:    ptrue p0.h
 ; CHECK-NEXT:    mov x8, sp
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -241,7 +249,7 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 2)
+  %res = call <vscale x 2 x half> @llvm.experimental.vector.splice.nxv2f16(<vscale x 2 x half> %a, <vscale x 2 x half> %b, i32 32)
   ret <vscale x 2 x half> %res
 }
 
@@ -279,31 +287,31 @@
 define <vscale x 4 x half> @splice_nxv4f16_first_idx(<vscale x 4 x half> %a, <vscale x 4 x half> %b) #0 {
 ; CHECK-LABEL: splice_nxv4f16_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #4
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 0)
+  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 1)
   ret <vscale x 4 x half> %res
 }
 
-define <vscale x 4 x half> @splice_nxv4f16_3_idx(<vscale x 4 x half> %a, <vscale x 4 x half> %b) #0 {
-; CHECK-LABEL: splice_nxv4f16_3_idx:
+define <vscale x 4 x half> @splice_nxv4f16_last_idx(<vscale x 4 x half> %a, <vscale x 4 x half> %b) #0 {
+; CHECK-LABEL: splice_nxv4f16_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #12
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #252
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 3)
+  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 63)
   ret <vscale x 4 x half> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
-define <vscale x 4 x half> @splice_nxv4f16_last_idx(<vscale x 4 x half> %a, <vscale x 4 x half> %b) #0 {
-; CHECK-LABEL: splice_nxv4f16_last_idx:
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
+define <vscale x 4 x half> @splice_nxv4f16_clamped_idx(<vscale x 4 x half> %a, <vscale x 4 x half> %b) #0 {
+; CHECK-LABEL: splice_nxv4f16_clamped_idx:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    str x29, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    addvl sp, sp, #-2
 ; CHECK-NEXT:    cntw x10
 ; CHECK-NEXT:    sub x10, x10, #1
-; CHECK-NEXT:    mov w9, #4
-; CHECK-NEXT:    cmp x10, #4
+; CHECK-NEXT:    mov w9, #64
+; CHECK-NEXT:    cmp x10, #64
 ; CHECK-NEXT:    ptrue p0.h
 ; CHECK-NEXT:    mov x8, sp
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -315,30 +323,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 4)
+  %res = call <vscale x 4 x half> @llvm.experimental.vector.splice.nxv4f16(<vscale x 4 x half> %a, <vscale x 4 x half> %b, i32 64)
   ret <vscale x 4 x half> %res
 }
 
-
 define <vscale x 8 x half> @splice_nxv8f16_first_idx(<vscale x 8 x half> %a, <vscale x 8 x half> %b) #0 {
 ; CHECK-LABEL: splice_nxv8f16_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #2
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 0)
+  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 1)
   ret <vscale x 8 x half> %res
 }
 
 define <vscale x 8 x half> @splice_nxv8f16_last_idx(<vscale x 8 x half> %a, <vscale x 8 x half> %b) #0 {
 ; CHECK-LABEL: splice_nxv8f16_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #14
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #254
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 7)
+  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 127)
   ret <vscale x 8 x half> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 8 x half> @splice_nxv8f16_clamped_idx(<vscale x 8 x half> %a, <vscale x 8 x half> %b) #0 {
 ; CHECK-LABEL: splice_nxv8f16_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -348,8 +355,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.h
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #8
-; CHECK-NEXT:    cmp x10, #8
+; CHECK-NEXT:    mov w9, #128
+; CHECK-NEXT:    cmp x10, #128
 ; CHECK-NEXT:    st1h { z0.h }, p0, [sp]
 ; CHECK-NEXT:    st1h { z1.h }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -357,7 +364,7 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 8)
+  %res = call <vscale x 8 x half> @llvm.experimental.vector.splice.nxv8f16(<vscale x 8 x half> %a, <vscale x 8 x half> %b, i32 128)
   ret <vscale x 8 x half> %res
 }
 
@@ -395,31 +402,31 @@
 define <vscale x 2 x float> @splice_nxv2f32_first_idx(<vscale x 2 x float> %a, <vscale x 2 x float> %b) #0 {
 ; CHECK-LABEL: splice_nxv2f32_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 0)
+  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 1)
   ret <vscale x 2 x float> %res
 }
 
-define <vscale x 2 x float> @splice_nxv2f32_1_idx(<vscale x 2 x float> %a, <vscale x 2 x float> %b) #0 {
-; CHECK-LABEL: splice_nxv2f32_1_idx:
+define <vscale x 2 x float> @splice_nxv2f32_last_idx(<vscale x 2 x float> %a, <vscale x 2 x float> %b) #0 {
+; CHECK-LABEL: splice_nxv2f32_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #248
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 1)
+  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 31)
   ret <vscale x 2 x float> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
-define <vscale x 2 x float> @splice_nxv2f32_last_idx(<vscale x 2 x float> %a, <vscale x 2 x float> %b) #0 {
-; CHECK-LABEL: splice_nxv2f32_last_idx:
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
+define <vscale x 2 x float> @splice_nxv2f32_clamped_idx(<vscale x 2 x float> %a, <vscale x 2 x float> %b) #0 {
+; CHECK-LABEL: splice_nxv2f32_clamped_idx:
 ; CHECK:       // %bb.0:
 ; CHECK-NEXT:    str x29, [sp, #-16]! // 8-byte Folded Spill
 ; CHECK-NEXT:    addvl sp, sp, #-2
 ; CHECK-NEXT:    cntd x10
 ; CHECK-NEXT:    sub x10, x10, #1
-; CHECK-NEXT:    mov w9, #2
-; CHECK-NEXT:    cmp x10, #2
+; CHECK-NEXT:    mov w9, #32
+; CHECK-NEXT:    cmp x10, #32
 ; CHECK-NEXT:    ptrue p0.s
 ; CHECK-NEXT:    mov x8, sp
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -431,29 +438,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 2)
+  %res = call <vscale x 2 x float> @llvm.experimental.vector.splice.nxv2f32(<vscale x 2 x float> %a, <vscale x 2 x float> %b, i32 32)
   ret <vscale x 2 x float> %res
 }
 
 define <vscale x 4 x float> @splice_nxv4f32_first_idx(<vscale x 4 x float> %a, <vscale x 4 x float> %b) #0 {
 ; CHECK-LABEL: splice_nxv4f32_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #4
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 0)
+  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 1)
   ret <vscale x 4 x float> %res
 }
 
 define <vscale x 4 x float> @splice_nxv4f32_last_idx(<vscale x 4 x float> %a, <vscale x 4 x float> %b) #0 {
 ; CHECK-LABEL: splice_nxv4f32_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #12
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #252
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 3)
+  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 63)
   ret <vscale x 4 x float> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 4 x float> @splice_nxv4f32_clamped_idx(<vscale x 4 x float> %a, <vscale x 4 x float> %b) #0 {
 ; CHECK-LABEL: splice_nxv4f32_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -463,8 +470,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.s
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #4
-; CHECK-NEXT:    cmp x10, #4
+; CHECK-NEXT:    mov w9, #64
+; CHECK-NEXT:    cmp x10, #64
 ; CHECK-NEXT:    st1w { z0.s }, p0, [sp]
 ; CHECK-NEXT:    st1w { z1.s }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -472,29 +479,29 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 4)
+  %res = call <vscale x 4 x float> @llvm.experimental.vector.splice.nxv4f32(<vscale x 4 x float> %a, <vscale x 4 x float> %b, i32 64)
   ret <vscale x 4 x float> %res
 }
 
 define <vscale x 2 x double> @splice_nxv2f64_first_idx(<vscale x 2 x double> %a, <vscale x 2 x double> %b) #0 {
 ; CHECK-LABEL: splice_nxv2f64_first_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #0
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 0)
+  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 1)
   ret <vscale x 2 x double> %res
 }
 
 define <vscale x 2 x double> @splice_nxv2f64_last_idx(<vscale x 2 x double> %a, <vscale x 2 x double> %b) #0 {
 ; CHECK-LABEL: splice_nxv2f64_last_idx:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #8
+; CHECK-NEXT:    ext z0.b, z0.b, z1.b, #248
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 1)
+  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 31)
   ret <vscale x 2 x double> %res
 }
 
-; Ensure index is clamped when we cannot prove it's less than VL-1.
+; Ensure index is clamped when we cannot prove it's less than 2048-bit.
 define <vscale x 2 x double> @splice_nxv2f64_clamped_idx(<vscale x 2 x double> %a, <vscale x 2 x double> %b) #0 {
 ; CHECK-LABEL: splice_nxv2f64_clamped_idx:
 ; CHECK:       // %bb.0:
@@ -504,8 +511,8 @@
 ; CHECK-NEXT:    sub x10, x10, #1
 ; CHECK-NEXT:    ptrue p0.d
 ; CHECK-NEXT:    mov x8, sp
-; CHECK-NEXT:    mov w9, #2
-; CHECK-NEXT:    cmp x10, #2
+; CHECK-NEXT:    mov w9, #32
+; CHECK-NEXT:    cmp x10, #32
 ; CHECK-NEXT:    st1d { z0.d }, p0, [sp]
 ; CHECK-NEXT:    st1d { z1.d }, p0, [x8, #1, mul vl]
 ; CHECK-NEXT:    csel x9, x10, x9, lo
@@ -513,7 +520,7 @@
 ; CHECK-NEXT:    addvl sp, sp, #2
 ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
 ; CHECK-NEXT:    ret
-  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 2)
+  %res = call <vscale x 2 x double> @llvm.experimental.vector.splice.nxv2f64(<vscale x 2 x double> %a, <vscale x 2 x double> %b, i32 32)
   ret <vscale x 2 x double> %res
 }