Index: llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
+++ llvm/include/llvm/CodeGen/GlobalISel/LegalizerInfo.h
@@ -357,6 +357,14 @@
 /// Keep the same scalar or element type as the given type.
 LegalizeMutation changeElementTo(unsigned TypeIdx, LLT Ty);
 
+/// Keep the same scalar or element type as \p TypeIdx, but take the number of
+/// elements from \p FromTypeIdx.
+LegalizeMutation changeElementCountTo(unsigned TypeIdx, unsigned FromTypeIdx);
+
+/// Keep the same scalar or element type as \p TypeIdx, but take the number of
+/// elements from \p Ty.
+LegalizeMutation changeElementCountTo(unsigned TypeIdx, LLT Ty);
+
 /// Change the scalar size or element size to have the same scalar size as type
 /// index \p FromIndex. Unlike changeElementTo, this discards pointer types and
 /// only changes the size.
Index: llvm/lib/CodeGen/GlobalISel/LegalizeMutations.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizeMutations.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizeMutations.cpp
@@ -43,6 +43,25 @@
   };
 }
 
+LegalizeMutation LegalizeMutations::changeElementCountTo(unsigned TypeIdx,
+                                                         unsigned FromTypeIdx) {
+  return [=](const LegalityQuery &Query) {
+    const LLT OldTy = Query.Types[TypeIdx];
+    const LLT NewTy = Query.Types[FromTypeIdx];
+    return std::make_pair(TypeIdx,
+                          OldTy.changeElementCount(NewTy.getElementCount()));
+  };
+}
+
+LegalizeMutation LegalizeMutations::changeElementCountTo(unsigned TypeIdx,
+                                                         LLT NewEltTy) {
+  return [=](const LegalityQuery &Query) {
+    const LLT OldTy = Query.Types[TypeIdx];
+    return std::make_pair(TypeIdx,
+                          OldTy.changeElementCount(NewEltTy.getElementCount()));
+  };
+}
+
 LegalizeMutation LegalizeMutations::changeElementSizeTo(unsigned TypeIdx,
                                                         unsigned FromTypeIdx) {
   return [=](const LegalityQuery &Query) {