diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -134,28 +134,31 @@
                           const TargetInstrInfo &TII, bool UseCopyInstr) {
     // Since Reg might be a subreg of some registers, only invalidate Reg is not
     // enough. We have to find the COPY defines Reg or registers defined by Reg
-    // and invalidate all of them.
-    SmallSet<MCRegister, 8> RegsToInvalidate;
-    RegsToInvalidate.insert(Reg);
+    // and invalidate all of them. Similarly, we must invalidate all of the
+    // the subregisters used in the source of the COPY.
+    SmallSet<MCRegUnit, 8> RegUnitsToInvalidate;
+    auto InvalidateCopy = [&](MachineInstr *MI) {
+      std::optional<DestSourcePair> CopyOperands =
+          isCopyInstr(*MI, TII, UseCopyInstr);
+      assert(CopyOperands && "Expect copy");
+
+      auto Dest = TRI.regunits(CopyOperands->Destination->getReg().asMCReg());
+      auto Src = TRI.regunits(CopyOperands->Source->getReg().asMCReg());
+      RegUnitsToInvalidate.insert(Dest.begin(), Dest.end());
+      RegUnitsToInvalidate.insert(Src.begin(), Src.end());
+    };
+
     for (MCRegUnit Unit : TRI.regunits(Reg)) {
       auto I = Copies.find(Unit);
       if (I != Copies.end()) {
-        if (MachineInstr *MI = I->second.MI) {
-          std::optional<DestSourcePair> CopyOperands =
-              isCopyInstr(*MI, TII, UseCopyInstr);
-          assert(CopyOperands && "Expect copy");
-
-          RegsToInvalidate.insert(
-              CopyOperands->Destination->getReg().asMCReg());
-          RegsToInvalidate.insert(CopyOperands->Source->getReg().asMCReg());
-        }
-        RegsToInvalidate.insert(I->second.DefRegs.begin(),
-                                I->second.DefRegs.end());
+        if (MachineInstr *MI = I->second.MI)
+          InvalidateCopy(MI);
+        if (MachineInstr *MI = I->second.LastSeenUseInCopy)
+          InvalidateCopy(MI);
       }
     }
-    for (MCRegister InvalidReg : RegsToInvalidate)
-      for (MCRegUnit Unit : TRI.regunits(InvalidReg))
-        Copies.erase(Unit);
+    for (MCRegUnit Unit : RegUnitsToInvalidate)
+      Copies.erase(Unit);
   }
 
   /// Clobber a single register, removing it from the tracker's copy maps.
diff --git a/llvm/test/CodeGen/AMDGPU/mcp-use-before-def.mir b/llvm/test/CodeGen/AMDGPU/mcp-use-before-def.mir
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/mcp-use-before-def.mir
@@ -0,0 +1,26 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 2
+# RUN: llc -mtriple=amdgcn-amd-amdhsa -verify-machineinstrs  -run-pass=machine-cp -o - %s | FileCheck %s
+
+# machine copy prop should not introduce use before def
+---
+name: back_copy_block
+body:           |
+  bb.0:
+    ; CHECK-LABEL: name: back_copy_block
+    ; CHECK: $vgpr20_vgpr21_vgpr22_vgpr23 = IMPLICIT_DEF
+    ; CHECK-NEXT: $vgpr10_vgpr11_vgpr12_vgpr13 = IMPLICIT_DEF
+    ; CHECK-NEXT: renamable $vgpr0_vgpr1 = V_MOV_B64_e64 killed $vgpr20_vgpr21, implicit $exec
+    ; CHECK-NEXT: renamable $vgpr20 = V_MOV_B32_e32 killed $vgpr1, implicit $exec
+    ; CHECK-NEXT: renamable $vgpr6_vgpr7_vgpr8_vgpr9 = COPY renamable $vgpr10_vgpr11_vgpr12_vgpr13
+    ; CHECK-NEXT: renamable $vgpr20 = V_MOV_B32_e32 killed $vgpr6, implicit $exec
+    ; CHECK-NEXT: S_ENDPGM 0, amdgpu_allvgprs
+    $vgpr20_vgpr21_vgpr22_vgpr23 = IMPLICIT_DEF
+    $vgpr10_vgpr11_vgpr12_vgpr13 = IMPLICIT_DEF
+    renamable $vgpr0_vgpr1 = V_MOV_B64_e64 killed renamable $vgpr20_vgpr21, implicit $exec
+    renamable $vgpr20 = V_MOV_B32_e32 killed renamable $vgpr1, implicit $exec
+    renamable $vgpr6_vgpr7_vgpr8_vgpr9 = COPY killed renamable $vgpr10_vgpr11_vgpr12_vgpr13
+    renamable $vgpr14_vgpr15 = COPY killed renamable $vgpr0_vgpr1
+    renamable $vgpr20 = V_MOV_B32_e32 killed renamable $vgpr6, implicit $exec
+    renamable $vgpr1_vgpr2_vgpr3_vgpr4 = COPY killed renamable $vgpr6_vgpr7_vgpr8_vgpr9
+    S_ENDPGM 0, amdgpu_allvgprs
+...