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
@@ -4045,22 +4045,30 @@
   let ElementSize = zprty.ElementSize;
 }
 
-multiclass sve_int_dup_imm_pred_merge<string asm> {
-  let Constraints = "$Zd = $_Zd" in {
-  def _B : sve_int_dup_imm_pred<0b00, 1, asm, ZPR8,  "/m", (ins ZPR8:$_Zd,  PPRAny:$Pg, cpy_imm8_opt_lsl_i8:$imm)>;
-  def _H : sve_int_dup_imm_pred<0b01, 1, asm, ZPR16, "/m", (ins ZPR16:$_Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i16:$imm)>;
-  def _S : sve_int_dup_imm_pred<0b10, 1, asm, ZPR32, "/m", (ins ZPR32:$_Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i32:$imm)>;
-  def _D : sve_int_dup_imm_pred<0b11, 1, asm, ZPR64, "/m", (ins ZPR64:$_Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i64:$imm)>;
-  }
-
-  def : InstAlias<"mov $Zd, $Pg/m, $imm",
-                  (!cast<Instruction>(NAME # _B) ZPR8:$Zd,  PPRAny:$Pg, cpy_imm8_opt_lsl_i8:$imm), 1>;
-  def : InstAlias<"mov $Zd, $Pg/m, $imm",
-                  (!cast<Instruction>(NAME # _H) ZPR16:$Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i16:$imm), 1>;
-  def : InstAlias<"mov $Zd, $Pg/m, $imm",
-                  (!cast<Instruction>(NAME # _S) ZPR32:$Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i32:$imm), 1>;
+multiclass sve_int_dup_imm_pred_merge_inst<
+    bits<2> sz8_64, string asm, ZPRRegOp zprty, ValueType intty,
+    ValueType predty, ValueType scalarty, imm8_opt_lsl cpyimm> {
+  let Constraints = "$Zd = $_Zd" in
+  def NAME : sve_int_dup_imm_pred<sz8_64, 1, asm, zprty,  "/m",
+                                  (ins zprty:$_Zd, PPRAny:$Pg, cpyimm:$imm)>;
   def : InstAlias<"mov $Zd, $Pg/m, $imm",
-                  (!cast<Instruction>(NAME # _D) ZPR64:$Zd, PPRAny:$Pg, cpy_imm8_opt_lsl_i64:$imm), 1>;
+                  (!cast<Instruction>(NAME) zprty:$Zd, PPRAny:$Pg, cpyimm:$imm), 1>;
+  def : Pat<(intty
+              (vselect predty:$Pg,
+                (intty (AArch64dup (scalarty (SVE8BitLslImm i32:$imm, i32:$shift)))),
+                intty:$Zd)),
+            (!cast<Instruction>(NAME) zprty:$Zd, $Pg, i32:$imm, i32:$shift)>;
+}
+
+multiclass sve_int_dup_imm_pred_merge<string asm> {
+  defm _B : sve_int_dup_imm_pred_merge_inst<0b00, asm, ZPR8, nxv16i8, nxv16i1,
+                                            i32, cpy_imm8_opt_lsl_i8>;
+  defm _H : sve_int_dup_imm_pred_merge_inst<0b01, asm, ZPR16, nxv8i16, nxv8i1,
+                                            i32, cpy_imm8_opt_lsl_i16>;
+  defm _S : sve_int_dup_imm_pred_merge_inst<0b10, asm, ZPR32, nxv4i32, nxv4i1,
+                                            i32, cpy_imm8_opt_lsl_i32>;
+  defm _D : sve_int_dup_imm_pred_merge_inst<0b11, asm, ZPR64, nxv2i64, nxv2i1,
+                                            i64, cpy_imm8_opt_lsl_i64>;
 
   def : InstAlias<"fmov $Zd, $Pg/m, #0.0",
                   (!cast<Instruction>(NAME # _H) ZPR16:$Zd, PPRAny:$Pg, 0, 0), 0>;
diff --git a/llvm/test/CodeGen/AArch64/sve-vselect-imm.ll b/llvm/test/CodeGen/AArch64/sve-vselect-imm.ll
--- a/llvm/test/CodeGen/AArch64/sve-vselect-imm.ll
+++ b/llvm/test/CodeGen/AArch64/sve-vselect-imm.ll
@@ -111,8 +111,10 @@
 ret <vscale x 2 x i64> %sel
 }
 
-; TODO: We could actually use something like "sel z0.b, p0/z, #-128" if the
-; odd bits of the predicate are zero.
+; TODO: We could actually use something like "cpy z0.b, p0/z, #-128". But it's
+; a little tricky to prove correctness: we're using the predicate with the
+; wrong width, so we'd have to prove the bits which would normally be unused
+; are actually zero.
 define <vscale x 8 x i16> @sel_16_illegal_wrong_extension(<vscale x 8 x i1> %p) {
 ; CHECK-LABEL: sel_16_illegal_wrong_extension:
 ; CHECK:       // %bb.0:
@@ -190,3 +192,225 @@
 %sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> zeroinitializer
 ret <vscale x 2 x i64> %sel
 }
+
+define <vscale x 16 x i8> @sel_merge_8_positive(<vscale x 16 x i1> %p, <vscale x 16 x i8> %in) {
+; CHECK-LABEL: sel_merge_8_positive:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.b, p0/m, #3 // =0x3
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 16 x i8> insertelement (<vscale x 16 x i8> undef, i8 3, i32 0), <vscale x 16 x i8> zeroinitializer, <vscale x 16 x i32> zeroinitializer
+%sel = select <vscale x 16 x i1> %p, <vscale x 16 x i8> %vec, <vscale x 16 x i8> %in
+ret <vscale x 16 x i8> %sel
+}
+
+define <vscale x 8 x i16> @sel_merge_16_positive(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_positive:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.h, p0/m, #3 // =0x3
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 8 x i16> insertelement (<vscale x 8 x i16> undef, i16 3, i32 0), <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i32> zeroinitializer
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> %vec, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_positive(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_positive:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.s, p0/m, #3 // =0x3
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 3, i32 0), <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> %vec, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_positive(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_positive:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.d, p0/m, #3 // =0x3
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 3, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}
+
+define <vscale x 16 x i8> @sel_merge_8_negative(<vscale x 16 x i1> %p, <vscale x 16 x i8> %in) {
+; CHECK-LABEL: sel_merge_8_negative:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.b, p0/m, #-128 // =0xffffffffffffff80
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 16 x i8> insertelement (<vscale x 16 x i8> undef, i8 -128, i32 0), <vscale x 16 x i8> zeroinitializer, <vscale x 16 x i32> zeroinitializer
+%sel = select <vscale x 16 x i1> %p, <vscale x 16 x i8> %vec, <vscale x 16 x i8> %in
+ret <vscale x 16 x i8> %sel
+}
+
+define <vscale x 8 x i16> @sel_merge_16_negative(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_negative:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.h, p0/m, #-128 // =0xffffffffffffff80
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 8 x i16> insertelement (<vscale x 8 x i16> undef, i16 -128, i32 0), <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i32> zeroinitializer
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> %vec, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_negative(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_negative:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.s, p0/m, #-128 // =0xffffffffffffff80
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 -128, i32 0), <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> %vec, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_negative(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_negative:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.d, p0/m, #-128 // =0xffffffffffffff80
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 -128, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}
+
+define <vscale x 16 x i8> @sel_merge_8_zero(<vscale x 16 x i1> %p, <vscale x 16 x i8> %in) {
+; CHECK-LABEL: sel_merge_8_zero:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.b, p0/m, #0 // =0x0
+; CHECK-NEXT:    ret
+%sel = select <vscale x 16 x i1> %p, <vscale x 16 x i8> zeroinitializer, <vscale x 16 x i8> %in
+ret <vscale x 16 x i8> %sel
+}
+
+define <vscale x 8 x i16> @sel_merge_16_zero(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_zero:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.h, p0/m, #0 // =0x0
+; CHECK-NEXT:    ret
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_zero(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_zero:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.s, p0/m, #0 // =0x0
+; CHECK-NEXT:    ret
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_zero(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_zero:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.d, p0/m, #0 // =0x0
+; CHECK-NEXT:    ret
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}
+
+define <vscale x 8 x i16> @sel_merge_16_shifted(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.h, p0/m, #512 // =0x200
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 8 x i16> insertelement (<vscale x 8 x i16> undef, i16 512, i32 0), <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i32> zeroinitializer
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> %vec, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_shifted(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.s, p0/m, #512 // =0x200
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 512, i32 0), <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> %vec, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_shifted(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov z0.d, p0/m, #512 // =0x200
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 512, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}
+
+; TODO: We could actually use something like "cpy z0.b, p0/m, #-128". But it's
+; a little tricky to prove correctness: we're using the predicate with the
+; wrong width, so we'd have to prove the bits which would normally be unused
+; are actually zero.
+define <vscale x 8 x i16> @sel_merge_16_illegal_wrong_extension(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_illegal_wrong_extension:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #128
+; CHECK-NEXT:    mov z1.h, w8
+; CHECK-NEXT:    mov z0.h, p0/m, z1.h
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 8 x i16> insertelement (<vscale x 8 x i16> undef, i16 128, i32 0), <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i32> zeroinitializer
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> %vec, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_illegal_wrong_extension(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_illegal_wrong_extension:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #128
+; CHECK-NEXT:    mov z1.s, w8
+; CHECK-NEXT:    mov z0.s, p0/m, z1.s
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 128, i32 0), <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> %vec, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_illegal_wrong_extension(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_illegal_wrong_extension:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #128
+; CHECK-NEXT:    mov z1.d, x8
+; CHECK-NEXT:    mov z0.d, p0/m, z1.d
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 128, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}
+
+define <vscale x 8 x i16> @sel_merge_16_illegal_shifted(<vscale x 8 x i1> %p, <vscale x 8 x i16> %in) {
+; CHECK-LABEL: sel_merge_16_illegal_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #513
+; CHECK-NEXT:    mov z1.h, w8
+; CHECK-NEXT:    mov z0.h, p0/m, z1.h
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 8 x i16> insertelement (<vscale x 8 x i16> undef, i16 513, i32 0), <vscale x 8 x i16> zeroinitializer, <vscale x 8 x i32> zeroinitializer
+%sel = select <vscale x 8 x i1> %p, <vscale x 8 x i16> %vec, <vscale x 8 x i16> %in
+ret <vscale x 8 x i16> %sel
+}
+
+define <vscale x 4 x i32> @sel_merge_32_illegal_shifted(<vscale x 4 x i1> %p, <vscale x 4 x i32> %in) {
+; CHECK-LABEL: sel_merge_32_illegal_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #513
+; CHECK-NEXT:    mov z1.s, w8
+; CHECK-NEXT:    mov z0.s, p0/m, z1.s
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 513, i32 0), <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer
+%sel = select <vscale x 4 x i1> %p, <vscale x 4 x i32> %vec, <vscale x 4 x i32> %in
+ret <vscale x 4 x i32> %sel
+}
+
+define <vscale x 2 x i64> @sel_merge_64_illegal_shifted(<vscale x 2 x i1> %p, <vscale x 2 x i64> %in) {
+; CHECK-LABEL: sel_merge_64_illegal_shifted:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #513
+; CHECK-NEXT:    mov z1.d, x8
+; CHECK-NEXT:    mov z0.d, p0/m, z1.d
+; CHECK-NEXT:    ret
+%vec = shufflevector <vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 513, i32 0), <vscale x 2 x i64> zeroinitializer, <vscale x 2 x i32> zeroinitializer
+%sel = select <vscale x 2 x i1> %p, <vscale x 2 x i64> %vec, <vscale x 2 x i64> %in
+ret <vscale x 2 x i64> %sel
+}