Index: llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -190,17 +190,6 @@
                              unsigned char OpFlags) const;
 
   // Optimization methods.
-
-  // Helper function to check if a reg def is an MI with a given opcode and
-  // returns it if so.
-  MachineInstr *findMIFromReg(unsigned Reg, unsigned Opc,
-                              MachineIRBuilder &MIB) const {
-    auto *Def = MIB.getMRI()->getVRegDef(Reg);
-    if (!Def || Def->getOpcode() != Opc)
-      return nullptr;
-    return Def;
-  }
-
   bool tryOptVectorShuffle(MachineInstr &I) const;
   bool tryOptVectorDup(MachineInstr &MI) const;
   bool tryOptSelect(MachineInstr &MI) const;
@@ -3342,12 +3331,12 @@
 
   // Begin matching the insert.
   auto *InsMI =
-      findMIFromReg(I.getOperand(1).getReg(), G_INSERT_VECTOR_ELT, MIB);
+      getOpcodeDef(G_INSERT_VECTOR_ELT, I.getOperand(1).getReg(), MRI);
   if (!InsMI)
     return false;
   // Match the undef vector operand.
   auto *UndefMI =
-      findMIFromReg(InsMI->getOperand(1).getReg(), G_IMPLICIT_DEF, MIB);
+      getOpcodeDef(G_IMPLICIT_DEF, InsMI->getOperand(1).getReg(), MRI);
   if (!UndefMI)
     return false;
   // Match the scalar being splatted.
@@ -3359,7 +3348,7 @@
     return false;
 
   // The shuffle's second operand doesn't matter if the mask is all zero.
-  auto *ZeroVec = findMIFromReg(I.getOperand(3).getReg(), G_BUILD_VECTOR, MIB);
+  auto *ZeroVec = getOpcodeDef(G_BUILD_VECTOR, I.getOperand(3).getReg(), MRI);
   if (!ZeroVec)
     return false;
   int64_t Zero = 0;
Index: llvm/test/CodeGen/AArch64/GlobalISel/opt-shuffle-splat.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/opt-shuffle-splat.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/opt-shuffle-splat.mir
@@ -108,3 +108,25 @@
     RET_ReallyLR implicit $q0
 
 ...
+---
+name:            splat_2xf64_copies
+alignment:       2
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+body:             |
+  bb.1.entry:
+    liveins: $d0
+
+    ; This test is exactly the same as splat_2xf64, except it adds two copies.
+    ; These copies shouldn't get in the way of matching the dup pattern.
+    %0:fpr(s64) = COPY $d0
+    %2:fpr(<2 x s64>) = G_IMPLICIT_DEF
+    %6:fpr(<2 x s64>) = COPY %2
+    %3:gpr(s32) = G_CONSTANT i32 0
+    %5:fpr(<2 x s32>) = G_BUILD_VECTOR %3(s32), %3(s32)
+    %1:fpr(<2 x s64>) = G_INSERT_VECTOR_ELT %6, %0(s64), %3(s32)
+    %7:fpr(<2 x s64>) = COPY %1
+    %4:fpr(<2 x s64>) = G_SHUFFLE_VECTOR %7(<2 x s64>), %2, %5(<2 x s32>)
+    $q0 = COPY %4(<2 x s64>)
+    RET_ReallyLR implicit $q0