Index: lib/CodeGen/MachineCopyPropagation.cpp
===================================================================
--- lib/CodeGen/MachineCopyPropagation.cpp
+++ lib/CodeGen/MachineCopyPropagation.cpp
@@ -52,6 +52,7 @@
 
     void SourceNoLongerAvailable(unsigned Reg);
     void CopyPropagateBlock(MachineBasicBlock &MBB);
+    bool eraseRedundantCopy(MachineInstr *MI, unsigned Src, unsigned Def);
 
     /// Candidates for deletion.
     SmallSetVector<MachineInstr*, 8> MaybeDeadCopies;
@@ -137,6 +138,31 @@
   return false;
 }
 
+bool MachineCopyPropagation::eraseRedundantCopy(MachineInstr *MI,
+                                                unsigned Src, unsigned Def) {
+  Reg2MIMap::iterator CI = AvailCopyMap.find(Src);
+  if (CI != AvailCopyMap.end()) {
+    MachineInstr *CopyMI = CI->second;
+    if (!MRI->isReserved(Def) && isNopCopy(CopyMI, Def, Src, TRI) &&
+        (!MRI->isReserved(Src) ||
+         NoInterveningSideEffect(CopyMI, MI, Src))) {
+      DEBUG(dbgs() << "MCP: copy is a NOP, removing: "; MI->dump());
+
+      // Clear any kills of Def between CopyMI and MI. This extends the
+      // live range.
+      for (MachineInstr &MMI
+           : make_range(CopyMI->getIterator(), MI->getIterator()))
+        MMI.clearRegisterKills(Def, TRI);
+
+      MI->eraseFromParent();
+      Changed = true;
+      ++NumDeletes;
+      return true;
+    }
+  }
+  return false;
+}
+
 void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
   DEBUG(dbgs() << "MCP: CopyPropagateBlock " << MBB.getName() << "\n");
 
@@ -152,40 +178,36 @@
              !TargetRegisterInfo::isVirtualRegister(Src) &&
              "MachineCopyPropagation should be run after register allocation!");
 
-      DenseMap<unsigned, MachineInstr*>::iterator CI = AvailCopyMap.find(Src);
-      if (CI != AvailCopyMap.end()) {
-        MachineInstr *CopyMI = CI->second;
-        if (!MRI->isReserved(Def) && isNopCopy(CopyMI, Def, Src, TRI) &&
-            (!MRI->isReserved(Src) ||
-             NoInterveningSideEffect(CopyMI, MI, Src))) {
-          // The two copies cancel out and the source of the first copy
-          // hasn't been overridden, eliminate the second one. e.g.
-          //  %ECX<def> = COPY %EAX<kill>
-          //  ... nothing clobbered EAX.
-          //  %EAX<def> = COPY %ECX
-          // =>
-          //  %ECX<def> = COPY %EAX
-          //
-          // Also avoid eliminating a copy from reserved registers unless the
-          // definition is proven not clobbered. e.g.
-          // %RSP<def> = COPY %RAX
-          // CALL
-          // %RAX<def> = COPY %RSP
-
-          DEBUG(dbgs() << "MCP: copy is a NOP, removing: "; MI->dump());
-
-          // Clear any kills of Def between CopyMI and MI. This extends the
-          // live range.
-          for (MachineInstr &MMI
-               : make_range(CopyMI->getIterator(), MI->getIterator()))
-            MMI.clearRegisterKills(Def, TRI);
-
-          MI->eraseFromParent();
-          Changed = true;
-          ++NumDeletes;
-          continue;
-        }
-      }
+      // The two copies cancel out and the source of the first copy
+      // hasn't been overridden, eliminate the second one. e.g.
+      //  %ECX<def> = COPY %EAX<kill>
+      //  ... nothing clobbered EAX.
+      //  %EAX<def> = COPY %ECX
+      // =>
+      //  %ECX<def> = COPY %EAX
+      //
+      // Also avoid eliminating a copy from reserved registers unless the
+      // definition is proven not clobbered. e.g.
+      // %RSP<def> = COPY %RAX
+      // CALL
+      // %RAX<def> = COPY %RSP
+      if (eraseRedundantCopy(MI, Src, Def))
+        continue;
+      // The two copies cancel out and the source of the first copy
+      // hasn't been overridden, eliminate the second one. e.g.
+      //  %ECX<def> = COPY %EAX<kill>
+      //  ... nothing clobbered EAX.
+      //  %EAX<def> = COPY %ECX
+      // =>
+      //  %ECX<def> = COPY %EAX
+      //
+      // Also avoid eliminating a copy from reserved registers unless the
+      // definition is proven not clobbered. e.g.
+      // %RSP<def> = COPY %RAX
+      // CALL
+      // %RAX<def> = COPY %RSP
+      if (eraseRedundantCopy(MI, Def, Src))
+        continue;
 
       // If Src is defined by a previous copy, the previous copy cannot be
       // eliminated.
Index: test/CodeGen/X86/machine-copy-prop.mir
===================================================================
--- test/CodeGen/X86/machine-copy-prop.mir
+++ test/CodeGen/X86/machine-copy-prop.mir
@@ -2,7 +2,22 @@
 
 --- |
   declare preserve_mostcc void @foo()
+  define void @copyprop0() { ret void }
   define void @copyprop1() { ret void }
+  define void @copyprop2() { ret void }
+...
+---
+# CHECK-LABEL: name: copyprop0
+# CHECK: bb.0:
+# CHECK-NEXT: %rax = COPY %rdi
+# CHECK-NOT: %rax = COPY %rdi
+# CHECK-NEXT: NOOP implicit %rax, implicit %rdi
+name: copyprop0
+body: |
+  bb.0:
+    %rax = COPY %rdi
+    %rax = COPY %rdi
+    NOOP implicit %rax, implicit %rdi
 ...
 ---
 # CHECK-LABEL: name: copyprop1
@@ -19,3 +34,18 @@
     %rdi = COPY %rax
     NOOP implicit %rax, implicit %rdi
 ...
+---
+# CHECK-LABEL: name: copyprop2
+# CHECK: bb.0:
+# CHECK-NEXT: %rax = COPY %rdi
+# CHECK-NEXT: CALL64pcrel32 @foo, csr_64_rt_mostregs, implicit %rsp, implicit-def %rsp
+# CHECK-NOT: %rax = COPY %rdi
+# CHECK-NEXT: NOOP implicit %rax, implicit %rdi
+name: copyprop2
+body: |
+  bb.0:
+    %rax = COPY %rdi
+    CALL64pcrel32 @foo, csr_64_rt_mostregs, implicit %rsp, implicit-def %rsp
+    %rax = COPY %rdi
+    NOOP implicit %rax, implicit %rdi
+...