Index: llvm/lib/CodeGen/MachineOutliner.cpp
===================================================================
--- llvm/lib/CodeGen/MachineOutliner.cpp
+++ llvm/lib/CodeGen/MachineOutliner.cpp
@@ -56,6 +56,7 @@
 //===----------------------------------------------------------------------===//
 #include "llvm/CodeGen/MachineOutliner.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/CodeGen/MachineFunction.h"
@@ -1245,31 +1246,53 @@
       // make sure that the ranges we yank things out of aren't wrong.
       if (MBB.getParent()->getProperties().hasProperty(
               MachineFunctionProperties::Property::TracksLiveness)) {
-        // Helper lambda for adding implicit def operands to the call
+        // The following code is to add implicit def operands to the call
         // instruction. It also updates call site information for moved
         // code.
-        auto CopyDefsAndUpdateCalls = [&CallInst](MachineInstr &MI) {
-          for (MachineOperand &MOP : MI.operands()) {
-            // Skip over anything that isn't a register.
-            if (!MOP.isReg())
-              continue;
-
-            // If it's a def, add it to the call instruction.
-            if (MOP.isDef())
-              CallInst->addOperand(MachineOperand::CreateReg(
-                  MOP.getReg(), true, /* isDef = true */
-                  true /* isImp = true */));
-          }
-          if (MI.isCandidateForCallSiteEntry())
-            MI.getMF()->eraseCallSiteInfo(&MI);
-        };
+        SmallSet<Register, 2> UseRegs, DefRegs;
         // Copy over the defs in the outlined range.
         // First inst in outlined range <-- Anything that's defined in this
         // ...                           .. range has to be added as an
         // implicit Last inst in outlined range  <-- def to the call
         // instruction. Also remove call site information for outlined block
-        // of code.
-        std::for_each(CallInst, std::next(EndIt), CopyDefsAndUpdateCalls);
+        // of code. The exposed uses need to be copied in the outlined range.
+        for (MachineBasicBlock::reverse_iterator Iter = EndIt.getReverse(),
+             Last = std::next(CallInst.getReverse());
+             Iter != Last; Iter++) {
+          MachineInstr *MI = &*Iter;
+          for (MachineOperand &MOP : MI->operands()) {
+            // Skip over anything that isn't a register.
+            if (!MOP.isReg())
+              continue;
+
+            if (MOP.isDef()) {
+              // Introduce DefRegs set to skip the redundant register.
+              DefRegs.insert(MOP.getReg());
+              if (UseRegs.count(MOP.getReg()))
+                // Since the regiester is modeled as defined,
+                // it is not necessary to be put in use register set.
+                UseRegs.erase(MOP.getReg());
+            } else if (!MOP.isUndef()) {
+              // Any register which is not undefined should
+              // be put in the use register set.
+              UseRegs.insert(MOP.getReg());
+            }
+          }
+          if (MI->isCandidateForCallSiteEntry())
+            MI->getMF()->eraseCallSiteInfo(MI);
+        }
+
+        for (const Register &I : DefRegs)
+           // If it's a def, add it to the call instruction.
+          CallInst->addOperand(MachineOperand::CreateReg(
+                  I, true, /* isDef = true */
+                  true /* isImp = true */));
+
+        for (const Register &I : UseRegs)
+          // If it's a exposed use, add it to the call instruction.
+          CallInst->addOperand(
+              MachineOperand::CreateReg(I, false, /* isDef = false */
+                                        true /* isImp = true */));
       }
 
       // Erase from the point after where the call was inserted up to, and
Index: llvm/test/CodeGen/AArch64/machine-outliner-side-effect.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/machine-outliner-side-effect.mir
@@ -0,0 +1,32 @@
+# RUN: llc -mtriple=aarch64 -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s
+
+# The test checks whether the compiler updates the side effect of function @OUTLINED_FUNCTION_0 by adding the use of register x20.
+
+--- |
+  declare void @spam() local_unnamed_addr
+  define void @baz() optsize minsize noredzone { ret void }
+...
+---
+name:            baz
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $x20
+
+    $x0 = COPY renamable $x20
+    BL @spam, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit-def $sp, implicit-def $x0
+    renamable $x21 = COPY $x0
+
+    $x0 = COPY renamable $x20
+    BL @spam, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit-def $sp, implicit-def $x0
+    renamable $x22 = COPY $x0
+
+    $x0 = COPY killed renamable $x20
+    BL @spam, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit-def $sp, implicit-def $x0
+    renamable $x3 = COPY $x0
+
+    RET_ReallyLR
+
+...
+
+# CHECK: BL @OUTLINED_FUNCTION_0, {{.*}}, implicit $x20, {{.*}}