Index: llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
===================================================================
--- llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
+++ llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
@@ -231,6 +231,8 @@
     }
   }
 
+  bool shouldFavorBackedgeIndex(const Loop *L) const;
+
   unsigned getGISelRematGlobalCost() const {
     return 2;
   }
Index: llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -16,6 +16,7 @@
 #include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/IntrinsicsAArch64.h"
+#include "llvm/IR/Use.h"
 #include "llvm/Support/Debug.h"
 #include <algorithm>
 using namespace llvm;
@@ -972,6 +973,36 @@
   return Considerable;
 }
 
+bool AArch64TTIImpl::shouldFavorBackedgeIndex(const Loop *L) const {
+  // This optimisation will generally introduce base address modifying
+  // instruction(s) into the preheader and is only really useful for
+  // unrolled loops, and we don't generally do when optimising for size.
+  if (L->getHeader()->getParent()->hasOptSize() ||
+      L->getNumBlocks() != 1)
+    return false;
+
+  // Find pointers with multiple uses within the loop.
+  DenseMap<Value *, unsigned> NumPointerUses;
+  for (auto &I : *L->getHeader()) {
+    if (I.getType()->isPointerTy())
+      NumPointerUses[&I] = 0;
+
+    for (auto &Use : I.operands()) {
+      if (!Use->getType()->isPointerTy())
+        continue;
+      if (NumPointerUses.count(Use))
+        NumPointerUses[Use]++;
+      else
+        NumPointerUses[Use] = 0;
+    }
+  }
+
+  return std::any_of(NumPointerUses.begin(), NumPointerUses.end(),
+                      [](detail::DenseMapPair<Value *, unsigned> Pair) {
+                        return Pair.second > 1;
+                      });
+}
+
 bool AArch64TTIImpl::useReductionIntrinsic(unsigned Opcode, Type *Ty,
                                            TTI::ReductionFlags Flags) const {
   auto *VTy = cast<VectorType>(Ty);