diff --git a/clang/include/clang/Basic/arm_mve.td b/clang/include/clang/Basic/arm_mve.td
--- a/clang/include/clang/Basic/arm_mve.td
+++ b/clang/include/clang/Basic/arm_mve.td
@@ -610,17 +610,10 @@
 defm vstrdq: scatter_offset_both<T.Int64, u64, 3>;
 
 multiclass PredicatedImmediateVectorShift<
-    Immediate immtype, string predIntrName, list<dag> unsignedFlag = []> {
-  foreach predIntr = [IRInt<predIntrName, [Vector, Predicate]>] in {
-    def _m_n: Intrinsic<Vector, (args Vector:$inactive, Vector:$v,
-                                      immtype:$sh, Predicate:$pred),
-       !con((predIntr $v, $sh), !dag(predIntr, unsignedFlag, ?),
-            (predIntr $pred, $inactive))>;
-    def _x_n: Intrinsic<Vector, (args Vector:$v, immtype:$sh,
-                                      Predicate:$pred),
-       !con((predIntr $v, $sh), !dag(predIntr, unsignedFlag, ?),
-            (predIntr $pred, (undef Vector)))>;
-  }
+    Immediate immtype, string predIntrName, dag unsignedFlag = (?)> {
+  defm "": IntrinsicMX<Vector, (args Vector:$v, immtype:$sh, Predicate:$pred),
+     !con((IRInt<predIntrName, [Vector, Predicate]> $v, $sh),
+          unsignedFlag, (? $pred, $inactive)), "_n">;
 }
 
 let params = T.Int in {
@@ -632,7 +625,7 @@
     def vshrq_n: Intrinsic<Vector, (args Vector:$v, imm_1toN:$sh),
                             (immshr $v, $sh, (unsignedflag Scalar))>;
     defm vshrq: PredicatedImmediateVectorShift<imm_1toN, "shr_imm_predicated",
-                                     [(unsignedflag Scalar)]>;
+                                     (? (unsignedflag Scalar))>;
   }
 }
 
@@ -713,25 +706,17 @@
 multiclass VectorComplexAddPred<dag not_halving, dag angle> {
   def "" : Intrinsic<Vector, (args Vector:$a, Vector:$b),
      (IRInt<"vcaddq", [Vector]> not_halving, angle, $a, $b)>;
-  def _m : Intrinsic<Vector, (args Vector:$inactive, Vector:$a, Vector:$b,
-                              Predicate:$pred),
+  defm "" : IntrinsicMX<Vector, (args Vector:$a, Vector:$b, Predicate:$pred),
      (IRInt<"vcaddq_predicated", [Vector, Predicate]>
        not_halving, angle, $inactive, $a, $b, $pred)>;
-  def _x : Intrinsic<Vector, (args Vector:$a, Vector:$b, Predicate:$pred),
-     (IRInt<"vcaddq_predicated", [Vector, Predicate]>
-       not_halving, angle, (undef Vector), $a, $b, $pred)>;
 }
 
 multiclass VectorComplexMulPred<dag angle> {
   def "" : Intrinsic<Vector, (args Vector:$a, Vector:$b),
     (IRInt<"vcmulq", [Vector]> angle, $a, $b)>;
-  def _m : Intrinsic<Vector, (args Vector:$inactive, Vector:$a, Vector:$b,
-                              Predicate:$pred),
+  defm "" : IntrinsicMX<Vector, (args Vector:$a, Vector:$b, Predicate:$pred),
     (IRInt<"vcmulq_predicated", [Vector, Predicate]> angle, $inactive, $a, $b,
       $pred)>;
-  def _x : Intrinsic<Vector, (args Vector:$a, Vector:$b, Predicate:$pred),
-    (IRInt<"vcmulq_predicated", [Vector, Predicate]> angle, (undef Vector), $a,
-      $b, $pred)>;
 }
 
 multiclass VectorComplexMLAPred<dag angle> {
diff --git a/clang/include/clang/Basic/arm_mve_defs.td b/clang/include/clang/Basic/arm_mve_defs.td
--- a/clang/include/clang/Basic/arm_mve_defs.td
+++ b/clang/include/clang/Basic/arm_mve_defs.td
@@ -432,6 +432,30 @@
   string basename = basename_;
 }
 
+// A wrapper to define both _m and _x versions of a predicated
+// intrinsic.
+multiclass IntrinsicMX<Type rettype, dag arguments, dag cg,
+                       string nameSuffix = "",
+                       PolymorphicNameType pnt_x = PNT_Type> {
+  // The _m variant takes an initial parameter called $inactive, which
+  // provides the input value of the output register, i.e. all the
+  // inactive lanes in the predicated operation take their values from
+  // this.
+  def "_m" # nameSuffix:
+     Intrinsic<rettype, !con((args rettype:$inactive), arguments), cg>;
+
+  // The _x variant leaves off that parameter, and simply uses an
+  // undef value of the same type.
+  def "_x" # nameSuffix:
+     Intrinsic<rettype, arguments, (seq (undef rettype):$inactive, cg)> {
+    // Allow overriding of the polymorphic name type, because
+    // sometimes the _m and _x variants polymorph differently
+    // (typically because the type of the inactive parameter can be
+    // used as a disambiguator if it's present).
+    let pnt = pnt_x;
+  }
+}
+
 // -----------------------------------------------------------------------------
 // Convenience lists of parameter types. 'T' is just a container record, so you
 // can define a typical intrinsic with 'let Params = T.Usual', or similar,