diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -1193,7 +1193,8 @@
 
   // Mark all used registers.
   BitVector UsedRegs(TRI.getNumRegs());
-  if (OnlyUsed)
+  if (OnlyUsed) {
+    const MachineRegisterInfo &MRI = MF.getRegInfo();
     for (const MachineBasicBlock &MBB : MF)
       for (const MachineInstr &MI : MBB)
         for (const MachineOperand &MO : MI.operands()) {
@@ -1202,9 +1203,10 @@
 
           MCRegister Reg = MO.getReg();
           if (AllocatableSet[Reg] && !MO.isImplicit() &&
-              (MO.isDef() || MO.isUse()))
+              MRI.isPhysRegModified(Reg))
             UsedRegs.set(Reg);
         }
+  }
 
   BitVector RegsToZero(TRI.getNumRegs());
   for (MCRegister Reg : AllocatableSet.set_bits()) {
diff --git a/llvm/test/CodeGen/AArch64/zero-call-used-regs.ll b/llvm/test/CodeGen/AArch64/zero-call-used-regs.ll
--- a/llvm/test/CodeGen/AArch64/zero-call-used-regs.ll
+++ b/llvm/test/CodeGen/AArch64/zero-call-used-regs.ll
@@ -22,8 +22,6 @@
 ; CHECK:       // %bb.0: // %entry
 ; CHECK-NEXT:    mul w8, w1, w0
 ; CHECK-NEXT:    orr w0, w8, w2
-; CHECK-NEXT:    mov x1, #0
-; CHECK-NEXT:    mov x2, #0
 ; CHECK-NEXT:    ret
 
 entry:
@@ -37,8 +35,6 @@
 ; CHECK:       // %bb.0: // %entry
 ; CHECK-NEXT:    mul w8, w1, w0
 ; CHECK-NEXT:    orr w0, w8, w2
-; CHECK-NEXT:    mov x1, #0
-; CHECK-NEXT:    mov x2, #0
 ; CHECK-NEXT:    mov x8, #0
 ; CHECK-NEXT:    ret
 
@@ -53,8 +49,6 @@
 ; CHECK:       // %bb.0: // %entry
 ; CHECK-NEXT:    mul w8, w1, w0
 ; CHECK-NEXT:    orr w0, w8, w2
-; CHECK-NEXT:    mov x1, #0
-; CHECK-NEXT:    mov x2, #0
 ; CHECK-NEXT:    ret
 
 entry:
@@ -68,8 +62,6 @@
 ; CHECK:       // %bb.0: // %entry
 ; CHECK-NEXT:    mul w8, w1, w0
 ; CHECK-NEXT:    orr w0, w8, w2
-; CHECK-NEXT:    mov x1, #0
-; CHECK-NEXT:    mov x2, #0
 ; CHECK-NEXT:    mov x8, #0
 ; CHECK-NEXT:    ret
 
diff --git a/llvm/test/CodeGen/X86/zero-call-used-regs.ll b/llvm/test/CodeGen/X86/zero-call-used-regs.ll
--- a/llvm/test/CodeGen/X86/zero-call-used-regs.ll
+++ b/llvm/test/CodeGen/X86/zero-call-used-regs.ll
@@ -28,7 +28,6 @@
 ; X86-64-LABEL: used_gpr_arg:
 ; X86-64:       # %bb.0: # %entry
 ; X86-64-NEXT:    movl %edi, %eax
-; X86-64-NEXT:    xorl %edi, %edi
 ; X86-64-NEXT:    retq
 
 entry:
@@ -44,7 +43,6 @@
 ; X86-64-LABEL: used_gpr:
 ; X86-64:       # %bb.0: # %entry
 ; X86-64-NEXT:    movl %edi, %eax
-; X86-64-NEXT:    xorl %edi, %edi
 ; X86-64-NEXT:    retq
 
 entry:
@@ -60,7 +58,6 @@
 ; X86-64-LABEL: used_arg:
 ; X86-64:       # %bb.0: # %entry
 ; X86-64-NEXT:    movl %edi, %eax
-; X86-64-NEXT:    xorl %edi, %edi
 ; X86-64-NEXT:    retq
 
 entry:
@@ -76,7 +73,6 @@
 ; X86-64-LABEL: used:
 ; X86-64:       # %bb.0: # %entry
 ; X86-64-NEXT:    movl %edi, %eax
-; X86-64-NEXT:    xorl %edi, %edi
 ; X86-64-NEXT:    retq
 
 entry: